"Les Rencontres de l'Observatoire"
ACTIVE GALACTIC NUCLEI:
FROM CENTRAL ENGINE TO HOST GALAXY
Meudon, France, 23-27 July 2002

02/19/02
Alexander Paul University of Cambridge
Department of Physics, Cavendish Laboratory, Madingley Road
CB3 0HE Cambridge, England
Presentation 1 : Poster
The environmental impact of FR-II radio sources
P. Alexander
FR-II radio sources have a very dramatic effect on their environment heating the ICM/IGM as they expand. However, the nature of this interaction depends critically on the properties (density profile, cooling time, thermal conductivity) of the surrounding gas. Simple physical models enable robust predictions to be made for X-ray appearance of the gas around FR-II sources and these are compared to recent CHANDRA data. Finally the long-term evolution of the cluster on time-scales long compared to the life-time of the source will be considered.
Presentation 2 : Poster
Simulations of the long-term evolution of cooling flow clusters containing radio sources
J. Basson, P. Alexander
We present simulations of the long-term evolution of cooling flow clusters containing a powerful FR-II radio source. The radio source has, as expected, a dramatic effect on the cluster for the period the source is initially expanding dragging cool gas from the centre of the cluster to large cluster radii. More surprisingly, the effects of the radio source can persist for periods long compared to the life-time of the source effecting both the cooling flow and the symmetry of the X-ray emission.
03/01/02
Aldcroft Tom Smithsonian Astrophysical Observatory
60 Garden St.
02138 Cambridge, USA
Presentation 1 : Poster
Deep Chandra observation of the lensed BALQSO UM425
Tom Aldcroft and Paul Green
We have obtained a 120 ksec Chandra ACIS-S exposure of UM425, a bright gravitationally lensed Broad Absorption Line (BAL) QSO. BALQSOs may exist in every quasar when seen at the proper orientation, or they may represent an early or high L/LEdd phase of quasar evolution. Our spectrum of UM425 (the brighter "A" component) has approximately 5000 counts, and is well fit with a power law (photon spectral index of 1.7) absorbed by a partially covering cloud having a Hydrogen column of 2.5 x 10^22 / cm^2. These parameters and the optical to X-ray slope are consistent with the interpretation that UM425 is a normal QSO which is hidden behind a shroud of obscuring material. We also examine the emission from the fainter lensed image UM425B, which is approximately 60 times fainter than UM425A in the optical. In the X-rays we find a ratio of 170, and we investigate possible sources of this discrepancy, including variability and absorption by the lensing galaxy.
09/05/01
Allen Mark Space Telescope Science Institute
3700 San Martin DriveHST imaging
21218 Baltimore, USA
Presentation 1 : Poster
STIS Ultraviolet Imaging of Low-Z 3CR Radio Galaxies.
M.G.Allen, W.B.Sparks, A.Koekemoer, A.R.Martel
We present ultraviolet images of 27 z < 0.1 3CR radio galaxies imaged at 2200 Angstroms with STIS. We compare the UV morphologies with WFPC2 snapshot survey images. We have found dramatic, complex and extended ultraviolet emission from radio galaxies even at zero redshift. We find a diverse range of UV morphologies, some completely divergent from their visual morphology, which are reminiscent of the chaotic high-z radio galaxies structures seen in rest-frame UV including star formation, jets, and possible scattered AGN continuum. We propose that these are the same physical phenomena as at high redshift, but on a smaller scale.
11/11/01
Alonso-Herrero Almudena Steward Observatory
933 N. Cherry Ave
AZ85721 Tucson, USA
Presentation 1 : Oral
An Infrared View of local universe AGN
Almudena Alonso-Herrero
In recent years, the advent of new infrared (IR) facilities (both space and ground-based) with superb spatial resolution and sensitivity has allowed us to make significant progress on the understanding of the IR properties of local universe AGN. In this talk I will summarize recent results obtained by our group on the IR properties of Seyfert and nearby radio galaxies. The IR emission in AGNs (Seyfert galaxies and radio quiet quasars) has often been interpreted as produced by a torus configuration where the dust is heated by the central source. However, until recently, the nuclear non-stellar IR continuum in Seyfert 2 galaxies had eluded us because of the dominance of the stellar emission shortward of 2 micron. From high resolution HST/NICMOS observations, we have now found that almost 100% of all Seyfert 1--1.9s and 50% of all Sy 2s show point sources at 1.6micron. This unresolved emission is variable in some of the Sy 2s and thus is presumably non-stellar emission (hot dust) associated with the central engine. We have put together non-stellar IR spectral energy distributions for a number of Seyfert and radio galaxies. Their modelling and the comparison between the infrared and hard X-ray properties of AGN has allowed us to demonstrate that the mid-IR emission (5-10micron) of local universe AGN is approximately an isotropic property, and thus it can be used as a good indicator of the AGN luminosity.
Presentation 2 : Poster
The SIRTF Spectral Energy Distributions of Luminous AGN
Almudena Alonso-Herrero, George H. Rieke, Dean Hines, et al.
The Unification Model proposes that various types of AGN (e.g., QSO vs. Hyperluminous Infrared Galaxy) are fundamentally similar in nature, but appear to have diverse properties because they are viewed at different angles. These aspect angles accentuate or de-emphasize emission at various wavelengths and from various regions near the central engine. The SIRTF AGN SED program is aimed to understanding the far-IR properties of Luminous AGN and will provide the SIRTF deep surveys with templates for classifying the newly discovered objects. We have selected a number of different AGN catalogs based on different observational properties, e.g., x-ray brightness, high frequency radio brightness, infrared emission, etc. From the complete AGN catalogs, we have drawn the most luminous examples (10-20 objects) at redshifts of z lower than 0.4. The use of previously well defined samples and the z lower than 0.4 redshift limit aids completeness and ensures access to large existing databases and high resolution imaging. We supplement the core sample with two small samples of AGNs at high redshift to probe evolutionary trends. This comparison will be particularly important for evaluating the effectiveness of our low-z SEDs as templates for identifying very high redshift AGNs.
03/01/02
Anderson James M New Mexico Tech/National Radio Astronomy Observatory
1003 Lopezville Rd
87801 Socorro NM, United States
Presentation 1 : Poster
Multi-Frequency VLBA Observations of Three LLAGN
James M. Anderson, James S. Ulvestad, Luis C. Ho
VLA observations of low-luminosity active galactic nuclei (LLAGN) have detected numerous flat-spectrum radio cores in nearby galaxies. Observations of three of theses sources (NGC 3147, 4203, and 4579) with the VLBA show slightly inverted spectra between 1.6 and 8.4 GHz, and are completely unresolved down to sizes of 2500 Schwarzschild radii. Here we will present results from VLBA observations between 8 and 43 GHz. ADAF-fueled LLAGN should remain unresolved at these higher frequencies with spectra that continue increasing, whereas jet-driven LLAGN may be resolved or have a spectral turnover.
02/05/02
Appleton Philip SIRTF Science Center, Caltech
Mailcode 220-6, 1200 E. California Blvd.
CA 91125 Pasadena, USA
Presentation 1 : Poster
The Host Galaxies of Low-luminosity AGN in the COLA Sample
P. N. Appleton
The COLA (Compact Object in Low-luminosity AGNs) sample is aimed at understanding the possible relationship between nuclear radio sources and their host galaxy environment. I will review the status of an all-sky IRAS-selected galaxy survey which includes CO, HI and optical observations of galaxies spanning a wide range of far-IR luminosity. In the northern sample, we have divided the galaxies into 5 classes based on the degree of galaxy-galaxy interaction (from isolated to violent mergers), and the dependence of the nuclear properties of the galaxies will be related to their large-scale dynamical state. The survey has relevance to the evolution of galaxies at high redshift since it provides a low-redshift baseline with which to compare interactions spread over cosmic time.
03/02/02
Baker Andrew MPE Garching
MPI fuer extraterrestrische Physik
Postfach 1312, D-85741 Garching, Germany
Presentation 1 : Poster
OVRO observations of molecular gas in active and inactive nuclei
Andrew J. Baker, Shardha Jogee, Kazushi Sakamoto, & Nick Z. Scoville
We present results from a multiple-line survey of fifteen nearby galactic nuclei conducted with the Owens Valley Radio Observatory millimeter array. Our sample galaxies span the full range of bar strength and include sources with Seyfert, LINER, and HII-region spectral classifications. High-resolution maps of CO(1-0), CO(2-1), and HCN(1-0) emission trace their distributions of molecular gas in different regimes of temperature and density. The inclusion of a control subsample of "inactive" nuclei is crucial in allowing us to test scenarios which relate the kinematic and physical properties of the fuel supply in a host galaxy to the apparent level of accretion activity in its center.
11/27/01
Baker Joanne University of Oxford
AStrophysics, DEpt Physics, Denys Wilkinson Building, Keble Rd
OX1 3RH Oxford, UK
Presentation 1 : Poster
Associated absorption in radio-loud quasars
J. Baker
We find that the strength of associated CIV absorption in quasars depends on the size, and hence age, of the radio source. Evidence is presented to show that the radio jets in quasars are triggered in a dusty gas-rich environment, which dissipates as the source grows.
02/05/02
Ballantyne David Institute of Astronomy
University of Cambridge
CB3 0HA Cambridge, United Kingdom
Presentation 1 : Poster
The properties of soft X-ray emission lines from accretion discs
D.R. Ballantyne, R.R. Ross & A.C. Fabian
I will present and discuss calculations of the soft X-ray emission features in the reflection spectra of photoionized accretion discs. We consider different ionization parameters, abundances and density distributions. The spectra exhibit lines from C VI, N VII, O VII, O VIII & Fe XVII-XVIII. For constant density models, the O VIII line typically has an EW < 100 eV. This can be made larger by increasing the O abundance, but this results in a much stronger O VII line. Hydrostatic models produce much weaker (EWs < 40 eV) and broader lines due to the presence of an ionized skin on the surface of the atmosphere. In all cases Compton broadening produces lines with a minimum width much larger than 10 eV. Therefore, it is unlikely that reflection from an ionized disc can produce strong soft X-ray emission lines with sharp blue wings.
01/19/02
Barth Aaron California Institute of Technology
Department of Astronomy, 105-24
91125 Pasadena, CA, USA
Presentation 1 : Poster
The Masses of Black Holes in BL Lac Objects
Aaron Barth
Recently, a tight correlation has been discovered between black hole mass and stellar velocity dispersion in galaxy bulges. We are carrying out a program to measure the stellar velocity dispersions in the host galaxies of low-redshift BL Lac objects, so that the black hole masses can be estimated by applying the M-sigma correlation. We will describe our results and the implications for the unification of BL Lac objects and radio galaxies.
Presentation 2 : Poster
Hubble Space Telescope Observations of LINER/HII "Transition" Galaxies
Aaron Barth, Luis Ho, and Alex Filippenko
About 15% of nearby galaxies have transition-type nuclei with emission line ratios that are intermediate between those of LINERs and normal HII regions. Various mechanisms have been proposed to explain the ionization of these objects, including ionization by unusually hot stars, shock excitation, and composite systems consisting of weak AGNs surrounded by star-forming regions. We have obtained new Hubble Space Telescope spectra, using a 0.2"-wide slit, of 15 transition nuclei in nearby galaxies, in order to spatially resolve the emission regions and constrain the excitation mechanisms and power sources. In this poster, we present preliminary results from this survey.
02/01/02
Bechtold Jill Steward Observatory, University of Arizona
933 N. Cherry Avenue
85721 Tucson, Arizona, USA
Presentation 1 : Oral
Chandra Survey of Radio-quiet, High Redshift Quasars
Bechtold et al.
We have observed 17 optically selected, radio-quiet high-redshift (z>4) quasars with the Chandra Observatory ACIS and detected 16 of them. When compared to low-redshift quasars observed with ROSAT, high redshift quasars are significantly more X-ray quiet, even when their extreme luminosity is taken into account. We also find that the X-ray spectral index of the high redshift objects is flatter than the average at low redshift. We show that these trends are predicted by models where the accretion flow is described by a cold, optically-thick accretion disk surrounded by a hot, optically thin corona, provided the viscosity alpha >=0.1, and the high redshift quasars have black holes with masses ~10^10 solar masses, accreting material at ~0.1 the Eddington limit.
08/30/01
Becker Robert UC-Davis & LLNL
L-413, LLNL
94550 Livermore, CA
Presentation 1 : Poster
The Highest Redshift Quasars and the Reddest Quasars
Becker, White, Fan, and a cast of thousands
We have been systematically searching a combination of the FIRST survey, the 2MASS survey, and the SDSS to discover very red quasars. Our efforts have uncovered two classes of objects: quasars at redshifts of 6 and beyond and quasars with extremely high extinction. The former are proving invaluable for probing the early universe. The latter are expanding our knowledge of red quasar populations. I will report on recent progress in both areas.
10/16/01
Beswick Robert Jodrell Bank Observatory, University of Manchester
Jodrell Bank Observatory, Macclesfield, Cheshire
SK11 9DL Macclesfield, U.K.
Presentation 1 : Poster
HI absorption against the radio galaxy 3C 293:Neutral Hydrogen towards the central Kiloparsec
Beswick, Pedlar, Taylor, Peck & Holloway
We will present recent results from a series of HI absorption observations of 3C 293 made using the GMRT, VLA + Pie Town, MERLIN, global VLBI and combinations of these data sets. Broad HI absorption is detected against the entire sub-arcsecond radio continuum source in all of these experiments. These observations have enabled us to trace the dynamics a distribution of HI on scales down to just a few pcs. We have detected large velocity gradients within the HI gas associated with the AGN which are interpreted as a ring of neutral gas located at a radius of only a few hundred parsecs from the nucleus.
09/04/01
Binette Luc Instituto de Astronomia
UNAM, Ap. 70-264,
04510 D.F. Mexico, Mexique
Presentation 1 : Poster
Can intergalactic gas explain quasar break near 1200Å ?
Luc Binette, Mario Rodríguez-Martínez and Isidro Ballinas, Instituto de Astronomía, UNAM, México
The ionizing spectral energy distribution of quasars exhibits a steepening of the distribution short-ward of 1200Å. The change of the power-law index from approximately -1 to -2 has so far been interpreted as being intrinsic to quasars. We consider the possibility that some of the steepening may result from a tenuous absorption component anticorrelated with large mass overdensities. EUV satellites whose detectors can extend down to 1000Å should set a usefull limit on such an absorption component by searching for an increase of quasar flux in the window 1050-1200Å respective to the extrapolation of the continuum above 1230Å.
02/19/02
Blackman Eric university of rochester
department of physics, university of rochester
14627 rochester, usa
Presentation 1 : Poster
Iron-line profiles from Four Non-Flat Disk Models
Eric G. Blackman, Sean A. Hartnoll
X-ray iron line profiles represent an important probe of the geometry and dynamics of the central accretion engine in AGN. Although a flat disk illuminated from above seems to work reasonably well in some cases, the noise in the current data and plausible disk physics invites some consideration of line profiles from non-flat disks for future comparison. Here I discuss some line profiles from concave discs, warped discs, clumpy thick discs, and disks with spiral structure, emphasizing their distinguishing and common features.
10/17/01
Blundell Katherine Oxford University Astrophysics
Keble Road
OX1 3RH Oxford, UK
10/22/01
Bochkarev Nikolai Sternberg State Astronomical Inst. at Lomonosov Moscow Univ.
Universitetskij Prospect, 13
119899 Moscow, Russia
Presentation 1 : Poster
Optical monitoring of AGN: history, results, problems, prospective
Bochkarev, N.G.
The role of photometric and monitoring programs in AGN research is discussed. History of monitoring programs is briefly described. Monitoring method input into determination of AGN size, mass, structure and kinematics is considered. Prospective of spectral and multi-colour photometric monitoring of AGN is briefly traced.
Presentation 2 : Poster
Correlation of optical and X-ray radiation of AGN
Novikova, O.A., Bochkarev, N.G.
We report the results of our study of correlation of optical and X-ray radiation of some AGN, specially: NGC 4151 and 3C390.3 as derived from low signal-to-noise data from All-Sky-Monitor of Rossi X-ray Timing Explorer (2-10 keV)and broad-band photometry of optical continuum, mainly that performed during several latest years at 4 CIS astronomical observatoreis in the frame of the "AGN Watch" Program.
03/05/01
Boisson Catherine observatoire de Paris-Meudon
5 Place J. Janssen
92195 Meudon, France
Presentation 1 : Poster
Stellar population synthesis of AGN from optical and IR spectroscopy
C. Boisson, M. Joly, D. Pelat
We are interested in the stellar content of AGN in relation with the evolution of the central activity. In this aim, we perform stellar population synthesis of the integrated starlight using a very powerful method dedicated to the determination of {\it the best solution} (among the many local solutions) in the stellar population synthesis problem. We are also able to calculate the error on the solution expected from the observational uncertainties. We will present the results obtained from observations in the optical and in the near IR (H band) of a sample of AGN. Preliminary results suggest an age sequence between starburst, Seyfert and normal galaxies.
03/28/02
Burbidge Margaret Center for Astrophysics & Space Sciences
University of California, San Diego
92093-0424 La Jolla, USA
Presentation 1 : Poster
The Ejection of QSOs from AGN: A phenomenon that cannot be denied
E. Margaret Burbidge and Geoffrey Burbidge
01/21/02
Cappi Massimo TeSRE-CNR
Via Gobetti 101,
40129 Bologna, Italy
Presentation 1 : Poster
XMM-Newton Survey of a Distance-limited Sample of Seyfert Galaxies
M. Cappi et al.
We are being performing an XMM-Newton study (275 ks awarded in the EPIC Guarantee Time) of a well-defined, complete, and statistically significant sample of the nearest (D<22Mpc) known 28 Seyfert galaxies. We present here the results from the >10 Seyferts observed to date, which illustrate well how this survey will allow a comprehensive study of nearby (low-luminosity) AGNs, as well as the serendipitous source populations of their host galaxies.
04/21/02
Cattaneo Andrea IAP Institut d'Astrophysique
98bis Bd Arago
75014 Paris, France
Presentation 1 : Poster
The radio dichotomy of quasars in cosmological simulations of galaxy formation
Andrea Cattaneo
I have studied the mass and spin evolution of supermassive black holes in Monte Carlo simulations of galaxy formation based on the Press-Schechter formalism. In field galaxies the black holes acquire most of their mass in a single accretion event, while refuellings and mergers with other black holes become more important in groups and clusters. I have also investigated if the assumption that radio jets are powered by the black hole rotation can explain the observed dichotomy in the radio properties of quasars. The simulations can reproduce a good agreement with the data but only if the accretion disc structure is such that effective despinning is still possible at high accretion rates close to the Eddington limit. The scenario considered in this study predicts that radio-loud quasars accrete matter at a lower fraction of the Eddington limit than radio-quiet ones.
11/11/01
Cecil Gerald University of North Carolina
Phillips Hall
27599-3255 Chapel Hill, NC, USA
Presentation 1 : Poster
STIS Maps of High-Velocity Gas in the NLR of NGC 1068: Connection to Coronal and Molecular Gas
Gerald Cecil
Our grid of STIS spectra span the NLR of NGC 1068 in [O III] and H-beta line emission, at 60 km/s and approx. 0."1 resolution. The spectra reveal numerous compact knots that are blueshifted up to 3200 km/s relative to galaxy systemic velocity, are located 70-150 pc from the nucleus, and range in velocity over 1250 km/s. The knots are generally located near the bright edges of the NLR, and each has KE at least 10^52 erg/ne4 (ne4 is gas density in units of 10^4 cm^-3). I will discuss how these knots appear to interact with other components of the NLR and the host galaxy, including the inner molecular torus and radio jet.
08/28/01
Celotti Annalisa S.I.S.S.A.
via Beirut 2-4
34014 Trieste, Italy
Presentation 1 : Poster
What jets are made of
Celotti A., Ghisellini G.
We discuss the nature of extragalactic jets and their content. Recent observations on different scales have in fact allowed to pose constraints on the role of electron-positron pairs vs ordinary electron proton plasma.
03/01/02
Chambers Ken Institute for Astronomy, University of Hawaii
2680 Woodlawn Drive
96822 Honolulu, USA
Presentation 1 : Poster
Bipolar outflows and the alignment effect in high redshift radio galaxies
K. C. Chambers
The alignment effect in high redshift radio galaxies can be modeled by an expanding outward-opening bipolar dust shell illuminated by a quasar nucleus. The model explains why QSRs have little or no extinction while allowing for the alignment effect in HZRGs to be dominated by dust scattering of a misdirected QSR. The velocity fields of the large scale extended emission lines are expected to include a redshifted echo of the emission lines from the QSR nucleus.
02/28/02
Charlot Patrick Observatoire de Bordeaux
2 Avenue de l'Observatoire, BP 89
33270 Floirac, France
Presentation 1 : Poster
Simultaneous VLBI and high-energy TeV observations of the gamma-ray blazar Mkn 421
P. Charlot, D. C. Gabuzda, H. Sol, B. Degrange, F. Piron
We report results of multi-frequency VLBI polarization observations of the gamma-ray blazar Mkn 421, coordinated with monitoring of its TeV emission with the CAT ground-based Cerenkov telescope. These observations revealed very obvious changes in the core region of Mkn 421 on time scales of a few weeks, at a time when it showed strong TeV activity. The paper will discuss possible correlations between radio core properties and high-energy events in the context of a VLBI-TeV connection.
08/28/01
Charmandaris Vassilis Cornell University
Astronomy Department, 106 Space Sciences Bld.
14853 Ithaca, USA
Presentation 1 : Poster
Search for diffuse extended mid-IR emission in Luminous IR Galaxies
V. Charmandaris, E. Le Floc'h, I.F. Mirabel
The discovery by IRAS of luminous (L$_{\rm IR}$ $>$10$^{11}$ L$_{\odot}$) and ultraluminous (L$_{\rm IR}$ $>$10$^{12}$ L$_{\odot}$) IR galaxies (LIRGs / ULIRGs) opened a new window in extragalactic astronomy, since it revealed that they are the dominant population of extragalactic objects in the local Universe (z$<$0.3). It is now widely accepted that i) nearly all ULIRGs are advanced mergers harboring powerful nuclear starbursts and/or enshrouded AGN, and ii) the mid-IR is powerful tracer of the star formation activity and bolometric luminosity of galaxies. The poor spatial resolution of IRAS though, due to the large ($\sim$1\,arcmin) pixels used, made it impossible to resolve the physical extent of the region which produces the bulk of their mid-IR emission. Recently, ground based 10 and 18\,$\mu$m imaging for a number of the nearest and brightest objects, has revealed compact nuclear emission from regions of just few arcsecs in diameter, (i.e. Soifer et al. 2001)., even though the ground measurements are hampered in sensitivity by the low mid-IR atmospheric transmission. Using ISOCAM, the most sensitive mid-IR camera to date, and the good spatial resolution images it provides we searched for extended emission from a sample of nearby luminous IR galaxies (Arp220, Arp299, NGC6240, VV114, IRAS14248-1447, IRAS19254-7245, IRAS23128-5919) for which the 5--16\,$\mu$m spectral energy distribution was available. We find that with the exception of VV114 more than 90\% of the integrated IRAS 12 micron flux originates from their nuclear regions ($\sim$5\,arcsec, $<$2\,kpc). This result suggests that the 10--15\,$\mu$m properties of distant unresolved ULIRGs would likely to also be dominated not by their disks, but by their nuclear region instead.
02/25/02
Chiaberge Marco Space Telescope Science Institute
3700 San Martin Drive
21218 Baltimore, MD, USA
Presentation 1 : Poster
The nuclei of FRI and FRII as seen by the HST: a further step towards a "fundamental plane" of radio galaxies?
M. Chiaberge, A. Capetti, A. Celotti, F.D. Macchetto, W.B. Sparks
We have studied the nuclei of 3CR radio galaxies with z lower than 0.3 through HST images, both in the optical and in the UV. The great majority of them show unresolved nuclear sources (central compact cores, CCC). We find a tight linear correlation between FRI CCC and the radio core emission, both in flux and luminosity, arguing for a non--thermal synchrotron origin of both components. FR II nuclei show a more complex behavior, which is however related to their optical spectral properties. Broad--lined objects (BLO) have the brightest nuclei both in the optical and in the UV. In the radio-optical plane BLO show an optical excess, when compared to the radio-optical correlation of FRI. About 40% of the high and low excitation galaxies (HEG and LEG) show CCC which resemble those detected in FRI galaxies, in apparent contrast to the unification model. The equivalent width of the [OIII] emission line reveals the nature of these nuclei. Most of HEGs nuclei are obscured to our line of sight and only scattered radiation is observed. LEGs (and a minority of HEGs) are instead truly similar to FRI. This implies that the population of FR II is composed by objects with different nuclear properties, and only a fraction of them can be unified with quasars. The different optical-UV spectral indices confirm the different nature of FRI and FRII nuclei: while the synchrotron scenario can account for the spectral properties of FRI CCC, the nuclei of BLO FRII are consistent with thermal radiation from the accretion disk. The UV data suggest that a moderate amount of obscuration (A_V ~ 1-3) can be present in FRI, but the obscuring material is not in a ``standard'' geometrically thick torus.
02/28/02
Christopher Micol California Institute of Technology
105-24 Caltech. 1201 East California Blvd.
91125 Pasadena, CA, USA
Presentation 1 : Poster
Molecular Gas in the Inner 3 Parsecs of Our Galaxy
M. Christopher, N. Scoville, S. Stolovy, M. Yun, and R. Coker
Using the Owens Valley Radio Observatory (OVRO) millimeter array, we have obtained the highest spatial (3.3" x 2.4") and spectral resolution HCN maps of the galactic center region. The prominent molecular emission comes from the circumnuclear disk (CND), a ring-like structure surrounding the galactic center at an inner radius of 1-1.5 parsecs. The CND is not a smooth structure, but rather is comprised primarily of 10-20 high density clouds with characteristic sizes of 8-10". From our observations we deduce a typical H_2 density within these clouds of a few x 10^6 cm^-3, corresponding to approximately a thousand solar masses of molecular gas in each cloud. The densities within these clouds are not high enough to prevent tidal disruption in the gravitational field of the galactic center (comprising both the massive black hole and the stellar population interior to the CND). Comparing our observed molecular gas emission with the ionized gas emission as seen in the Paschen Alpha NICMOS map from Scoville et al. (2002), there is clear evidence for interplay between the ionized and molecular gas (e.g. the western arc in ionized gas is the photoionized edge of the CND and streamers within the CND spatially and kinematically connect with the Northern Arm of ionized gas). Examining the interaction of the molecular and ionized gas within the central parsecs of the galaxy sheds observational light on conditions near massive black holes, a critical tool for understanding AGN phenomenon.
Presentation 2 : Poster
Keck H and K Spectroscopy of UGC5101: Probing the AGN and Starburst Components
M. Christopher, N. Scoville, E. Schinnerer, L. Armus and D. Frayer
UGC5101 is an ultraluminous infrared galaxy (ULIRG) at a redshift of 0.04. Using NIRSPEC on the Keck Telescope, we have obtained H and K band spectroscopy of UGC5101 with a seeing of 0.5". The excellent seeing conditions allow us to probe the conditions at a close distance to the central nucleus. By examining the equivalent widths of the CO bandheads located in the H and K bands, we have traced the stellar population, and we find convincing evidence for a central starburst containing red supergiants. In addition, equivalent width measurements of the lines of Brackett Gamma and molecular hydrogen as well as absorption lines have shown strong evidence for a central dilution consistent with a central hot dust source. Our spectra also include one starburst cluster (identified in NICMOS imaging by Scoville et al. 2000) lying approximately 4" from the central nucleus of UGC5101, and we analyze the stellar population of that cluster and compare that to the population of the nuclear region.
10/16/01
Cid Fernandes Roberto Universidade Federal de Santa Catarina
Depto. de Fisica - CFM - UFSC - Campus Universitario - Trindade - PO Box: 476
88040-900 Florianopolis, SC, Brazil
Presentation 1 : Oral
Starbursts around Seyfert Nuclei - What do we know about them
R Cid Fernandes, T Heckman, T Strochi Bergmann, R Gonzalez Delgado, H Schmitt, N Levenson
We present a comparative study of 15 composite starburst + Seyfert 2 galaxies and 20 ``pure''/``boring'' Seyfert 2's (those where star-formation has not been detected). Composites are defined as nuclei which show the direct (but difficult-to-detect) spectroscopic signatures of the hot massive stars that power circum-nuclear starbursts: UV stellar wind lines, WR features and/or high order Balmer absorption lines. We examine a variety of more-easily-measured quantities for this sample, such as the equivalent widths of strong absorption features, continuum colors, emission-line equivalent widths, emission line ratios and profiles, far-IR luminosities, and near-UV surface brightness. Our goals are to verify whether these properties of the composite nuclei are consistent with the expected impact of a starburst, and to investigate alternative less-demanding methods to infer the presence of starbursts in Seyfert 2 nuclei, applicable to larger samples. We find that starbursts do indeed leave clear and easily quantifiable imprints on the near-UV to optical continuum and emission line properties of Seyfert 2's. Composite systems can be recognized by: (1) a strong ``Featureless Continuum'', which dilutes the Ca K line from old bulge stars to $W_K< 10$ \AA; (2) emission lines whose equivalent widths are intermediate between Starburst galaxies and ``pure'' Seyfert 2's; (3) relatively low excitation line-ratios, which indicate that part of the gas ionization in these Seyfert 2's (typically $\sim 50\%$ of H$\beta$) is due to photoionization by OB stars; (4) large far IR luminosities ($> 10^{10}$ L$_\odot$); (5) High near-UV surface brightness ($\sim 10^3$ L$_{\odot}$ pc$^{-2}$). These characteristics are all consistent with the expected impact of circum-nuclear starbursts on the observed properties of Seyfert 2's. Furtheremore, they offer cheap and easy-to-aply alternative empirical diagnostics of the presence of circum-nuclear starbursts. We also find strong evidence for an evolutionary scenario, in which luminous composite systems evolve towards weak and ``pure'' Seyfert 2's. For various and technical and (mostly) historical reasons, other classes of AGN have not been carefully scrutinized for the presence of circum-nuclear starbursts, hindering a more panoramic understanding of the starburst-AGN connection. Do LINERs, transition objects and type 1 Seyferts also have circum-nuclear starbursts? We present some ``hot-off-the-dome'' observational results which answer this question. We conclude that, as a whole, the once herectic subject of the starburst-AGN connection has finally come off age. Slowly but syrely, these new evidence is helping us figure the roles of starbursts and black-holes in AGN.
11/09/01
Clénet Yann Observatoire de Paris
5 place Jules Janssen
92190 Meudon, France
Presentation 1 : Poster
First observations of AGNs with NAOS/CONICA and GriF
Y. Clénet, D. Gratadour, D. Rouan, E. Gendron, F. Lacombe
Our team from LESIA (Observatoire de Paris) has just benefited from the installation of two new instruments: NAOS/CONICA, the VLT adaptive optics system and its infrared camera, and GriF, the 3-D spectrograph coupled with the CFHT adaptive optics system PUEO. In the quest for the detection of the internal morphological structures invoked by the unified model in active galactic nuclei (molecular disk, dust/gas torus, cusp, micro-bars and micro-spirals), high spatial resolution is mandatory since their predicted size, from 1 to 100 pc, even for the nearest AGNs (15 Mpc for example for NGC 1068) corresponds to subarcsecond dimensions. Thanks to adaptive optics, a spatial scale as small as 2.5 pc (resp. 6 pc) is now accessible on NGC 1068 in imaging and spectroscopy with NAOS/CONICA (resp. GriF). Recently, the long-slit spectroscopic mode of GriF was used for the first time to observe the central part of NGC 1068 and the first observations of AGNs made with NAOS/CONICA were performed on the Sombrero galaxy (M104) and NGC 3081 during commissionning phase. Preliminary results from these observations will be presented in a poster during this conference.
08/28/01
Clavel Jean ESA
P.O. Box 50727
28080 Madrid, Spain
Presentation 1 : Poster
XMM observations of the BALQSO LBQS 2212-1759
J. Clavel, N. Schartel, M. Santos, M. Guainazzi
The Broad Absorption Line Quasar (BALQSO) LBQS 2212-1759 was observed with XMM-Newton for 115 ks. Despite its large optical brightness, the quasar is not detected in neither of the three X-ray XMM telescopes. The very long exposure time, coupled with the exceptionally low level of background during the observation and the combined large effective area of the three XMM telescopes yield very stringent upper limits on the X-ray flux of LBQS 2212-1759. For reasonable values of the 0.1-10 keV and optical-to-X-ray spectral indices, this translates into a stringent lower limit on the absorbing column density in front of the X-ray source. This confirms the suspicion that BALQSO are heavily absorbed sources. The serendipitous content of the deep exposure of the 30 arcmin field around LBQS 2212-1759 is also analysed.
07/18/01
Collin Suzy observatoire de Paris-Meudon
5 Place J. Janssen
92195 Meudon, France
Presentation 1 : Poster
Influence of thermal instability on the AGN spectrum
S. Coup\'e, A-M.Dumont, S. Collin
It is well-known that thermal instability leads to the coexistence of two or more phases in the atmosphere of irradiated disks in AGN, or more generally in an irradiated medium where the pressure is imposed. We study the impact on the emitted spectrum, and we show that for models corresponding to the same given parameters (external pressure, irradiating flux and spectrum, abundances, column density) it can lead to large uncertainties on the emitted spectrum, as for instance on the X-ray line intensities or on the slope of the continuum.
07/17/01
Combes Francoise Observatoire de Paris
61 Av. de l'Observatoire
F-75014 Paris, France
Presentation 1 : Invited
AGN Fueling: The Observational Point of View
Observations at multiple wavelengths are reviewed to search for evidence for fueling mechanisms in galaxies, both for nuclear starbursts and AGN activity. Although it is undisputed that dynamical perturbations such as bars or tidal interactions accumulate gas in the central regions and sometimes trigger nuclear starbursts, the evidence remains scarce that these are necessary to fuel AGNs. Interpretations in terms of time-scales, feed-back, and black hole evolution will be discussed.
08/29/01
Corbett Elizabeth Anglo-Australian Observatory
PO Box 296
1710 Epping, NSW, Australia
Presentation 1 : Poster
The relationship between line width and luminosity in composite QSO spectra.
E. Corbett, H. Netzer, S. Croom, B. Boyle, K. Rhook, N. Loaring, L.Miller, P. Outram, T. Shanks, R.J. Smith.
We have measured the widths of the major emission lines ( e.g narrow [OIII] $\lamda \lamda$ 4959,5007, [OII] \lam3727 and broad CIV) in composite QSO spectra generated from over 22000 individual low resolution ($\sim8$\AA) QSO spectra from the 2dF ($18.25<\bj<20.85$) and 6dF ($16<\bj\leq18.25$) QSO Redshifts Surveys. Each composite spectrum covers a relatively narrow range in redshift ($\Delta z=0.25$) and absolute magnitude ($\Delta \mb=0.5$) with a typical signal-to-noise ratio of over 100. We find strong evidence that the line width of several of the emission lines, including [OIII], H$\beta$ and CIV, is correlated with the QSO luminosity. We discuss the implications of these results for studies of QSO emission line regions and the luminosity - black hole mass relationship.
09/28/01
Coupe Severine Observatoire de Paris-Meudon
5 place Jules Janssen
92195 Meudon, France
Presentation 1 : Poster
Influence of the column-density on the n=2 complex of He-like ions
S. Coup\'e, A.M.Dumont, M.C. Artru
We present new calculations performed with our transfer code, Titan, with updated atomic data. In particular we show the influence of the column-density on the population of the n=2 complex of He-like ions, those latter being widely used to provide diagnostics in optical thin plasma using the so-called x, y, z and w lines. We apply those diagnostics to optical thick photoionised plasma and compare them with the optical thin case.
12/06/01
Courbin Frederic PUC, Chile / Univ. Liege, Belgium / GEPI, France
Liege, Belgium (to be updated later since the institute being moved !)
XXXX Liege, Belgium
Presentation 1 : Poster
Spatially resolved on-axis VLT spectroscopy of quasar host galaxies
Courbin, Letawe, Wisotzki, Magain, Jablonka, Alloin
We present the first results of on ongoing effort to perform spatially resolved on-axis spectroscopy of quasar host galaxies at low (z~0.1-0.3) redshift. The science goal of the project are described and focus on the determination of the gas and stellar contents of the quasar hosts and on the study of their dynamics. The technical details of a new spectra deconvolution method are also presented. It allows one to obtain spatially resolved spectra of quasar hosts, decontaminated from the light of the central quasar. Applications to deep, high spectral resolution VLT data are shown. In particular we present rotation curves for the central kiloparsec of quasar hosts. The long term goals of project are finally described, in particular in view of the use of 2D spectrographs such as GIRAFFE or SINFONI.
08/31/01
Courvoisier Thierry ISDC
16, ch. d'Ecogia
ch-1290 Versoix, Switzerland
Presentation 1 : Poster
quasars, seyfert galaxies and stars
Courvoisier

Presentation 2 : Poster
AGN with INTEGRAL and other high energy instruments
courvoisier
02/26/02
Crenshaw D. Michael Georgia State University
One Park Place South SE, Suite 700
30303 Atlanta, GA, USA
Presentation 1 : Poster
On the Origin of Intrinsic Absorbers in AGN
Crenshaw and Kraemer
Recent UV, optical, and X-ray observations of Seyfert 1 galaxies are providing information on the radial locations of the intrinsic absorbers with respect to their nuclei, which is crucial for understanding the origin of this outflowing gas. A correlation between saturated UV absorption lines near systemic velocity, reddening (as measured by UV colors), and inclination of the host galaxy allow the identification of absorbers that originate at large distances (> 100 pc) in the plane of the host galaxy. Fine-structure and metastable UV absorption lines can be used to determine the densities; combined with photoionization models and X-ray constraints, they provide the locations of the inner absorbers (e.g., the high column absorber in NGC 4151 is only ~0.03 pc from the nucleus). Finally, multi-wavelength monitoring campaigns, such as the recent one on NGC 3783, provide densities and distances of the absorbers from the response of the absorption columns to ionization changes.
02/28/02
Cruz Fidel INSTITUTO DE ASTRONOMIA, UNAM.)
P.O. Box 439027
92143-9027 San Diego, CA, USA
Presentation 1 : Poster
Galactic cold collapse with a supermassive black hole
Fidel Cruz, Hector Velazquez
We present N-body simulations of dissipationless cold collapse with and without a primordial central black hole. Our preliminary results show that the presence of the BH allows the formation of a central cuspy profile with a slope close to the observed values.
02/28/02
De Breuck Carlos IAP, Paris
98bis Bd Arago
F-75014 Paris, France
Presentation 1 : Poster
03/01/02
Degrange Bernard Lab Phys Nucleaire Haute Energie
Ecole Polytechnique
91128 Palaiseau Cedex, France
11/26/01
Deluit Sandrine INTEGRAL Science Data Center (ISDC) and Geneva Observatory
16, Chemin d'Ecogia
ch-1290 Versoix, Switzerland
Presentation 1 : Poster
Investigating The Properties Of The Intrinsic Emission Of Seyfert 1 And Seyfert 2 Galaxies
Sandrine Deluit
We present the results of a study of the hard X-ray spectra of all the Sy 1 and Sy 2 galaxies as observed with the PDS (15-200 keV) aboard BeppoSAX. The aim of this study is to compare the intrinsic emission of a large sample of Seyfert galaxies (14 Sy1, 10 Sy 1.5 and 22 Compton thin Sy2) to test the unified model according to which Sy1 and Sy2 have the same nucleus. We built the average spectra of the different classes of Sy galaxies in order to compare their spectral properties at energies where absorption effects play no role and where we have a direct access to the central engine. We discuss the differences and common properties of the spectra and present a new vision of the unified model.
12/13/01
Dietrich Matthias Department of Astronomy, University of Florida
211 Bryant Space Center
32611-2055 Gainesville, USA
Presentation 1 : Poster
Correlations of Continuum and Emission Line Properties of Quasars
Matthias Dietrich, Fred Hamann, Joe Shields
We report on the analysis of a large quasar sample (~750), covering a redshift range from z=0 to 5 and nearly 6 orders of magnitude in continuum luminosity. Correlations of continuum and emission line properties in the ultraviolet and optical spectral range will be discussed. The well established Baldwin-effect is detected for almost all emission lines from OVI1034 to [OIII]5007. The anti-correlation provides evidence that the strength of the Baldwin-effect is related to the ionization energy of the individual ions. Furthermore, indications of a curvature in the relation will be discussed in the framework of evolutionary models assuming an anisotropic and luminosity dependent SED of the continuum.
04/18/02
Di Matteo Tiziana Max-Planck-Institut fuer Astrophysik
Karl Schwarschild Str. 1
D-85741 Garching, Germany
Presentation 1 : Poster
Black hole fuelling and accretion in low luminosity systems: the case of M87
Di Matteo T., Allen, S.W, Fabian A.C., Wilson, A, Young A.
Chandra observations of nearby galactic nuclei have allowed us to make significant progress in understanding why their central supermassive black holes are so dim. We examine the constraints on accretion disk models and on fuelling of the central black hole (and its relation to jet activity) for the nucleus of the giant elliptical galaxy M87, one of the most illustrative object within the class of low luminosity nuclei. Chandra X-ray observations of M87, for the first time, resolve the thermal state of the hot interstellar medium within the accretion (Bondi) radius of its central $3 \times 10^9 M_{\odot} $ black hole. This implies a Bondi accretion rate, $\dot{M}_{Bondi} \sim 0.1 M_{\odot}$yr$^{-1}$. The X-ray luminosity of the active nucleus of M87 observed with {\it Chandra} is $L_{x} \sim 7 \times 10^{40}$ erg s$^{-1}$. This greatly exceeds the predicted nuclear luminosity, $L_{\rm Bondi} \sim 5 \times 10^{44}$ erg s$^{-1}$, for accretion at the Bondi rate with a canonical accretion radiative efficiency of 10\%. We show that low radiative efficiency accretion flow models are consistent with the observations. However, the predicted Bondi nuclear power is consistent with the overall energetics of the system (and in particular with the kinetic energy of the jet). This suggests that either most of the accretion energy is released in the jet or that the central engine of M87 undergoes on-off activity cycles. We show that at present, the energy dumped into the ISM by the jet may reduce the accretion rate onto the black hole sufficiently to account for its low luminosity.
03/01/02
Djannati-Ataï Arache PCC-Collège de France
11, Place Marcelin Berthelot
75231 Paris Cx05, France
Presentation 1 : Oral
The BL Lac object 1ES1426+428 emission above 300 GeV as detected by the CAT telescope
A. Djannati-Ataï for the CAT collaboration
The BL Lac Object 1ES1426+428, at a redshift of 0.129, has been observed by the CAT telescope during 26 hours from february 1998 to June 2000. A gamma-ray signal of 248 events above 300 GeV at 4.7 standard- deviations has been detected, corresponding to a flux of 0.2 Crab. Although poorly determined due to low statistics, the spectrum seems very steep and supports the expected absorption effect by the Intergalactic Infrared field.
02/26/02
Donea Alina-Catalina University of Adelaide, also Astron. Inst. of Romanian Academy
Department of Physics and Mathematical Physics
5005 Adelaide, Australia
Presentation 1 : Poster
How relevant is the torus geometry for the TeV gamma-rays emitted in the AGN jets?
A.-C. Donea, R.J. Protheroe
Motivated by unification schemes of active galactic nuclei, we review evidence for the existence of small-scale dust tori and BLR in BL Lacs and Fanaroff-Riley Class I radio galaxies. Since there is no direct evidence of any thermal emission from tori the task we search for indirect evidence (at any wavelength) for dust structures in the centres of host galaxies. We propose that an existing jet-accretion disk symbiosis can be extrapolated to provide a large scale-symbiosis between other important dusty constituents of the blazar/FR-I family. In the context of this symbiosis we discuss the interactions of GeV and TeV gamma-rays produced in the jet with the infrared radiation fields external to the jet in quasars and blazars, taking account the anisotropy of the radiation. We also review what kind of torus geometry would fit observations of quasars and blazars made at different wavelengths best.
09/10/01
Dopita Michael Research School of Astronomy & Astrophysics, Aust. Nat. Univ.
Cotter Road
ACT 2611 Weston Creek, Australia
Presentation 1 : Invited
The (Dynamical & Excitation) Evolution of the Narrow Line Region
Michael A. Dopita
I will present an integrated (theoretical) view of the temporal development of the extended narrow line regions in AGN. This will attempt to show how hydrodynamical modelling, shocks, classical photoionisation models, and the new dusty, radiation-pressure dominated outflow models all have their role and how they fit together into the "big picture".
Presentation 2 : Poster
Star Formation Rates in Colliding Galaxies
Michael A. Dopita, Lisa Kewley, Elizabeth Corbett, Ray Norris, Curtis Struck, Phil Appleton, Vassilis Charmandaris
We present H-alpha imaging of the star-forming regions in a large sample of southern IRAS galaxies which are selected to be colliding, merging or post-merger systems. We investigate the distribution of star formation and its evolution during the merger, and compare the star formation rates detewrmined from H-alpha photometry with those determined from the far-IR emission.
09/04/01
Doroshenko Valentina Crimean Laboratory of Sternberg Astronomical Institute
p. Nauchny, 6-9
98409 Crimea, Ukraine
Presentation 1 : Poster
Spectral activities of the Seyfert galaxy Mkn 6 during 1970-1990
Doroshenko V.T., Sergeev S.G., Pronik V.I.
We present results of an optical spectral observations of the Seyfert galaxy Markarian 6 during 1970 - 1990 carried out with image-tube spectrograph at the 2.6-m Shajn Telescope of the Crimean Astrophysical Observatory. Our data set consists of about 100 spectra in Hbeta and ~100 spectra in Halpha regions.
Presentation 2 : Poster
UBV photometry of Markarian 6 in 1986-2001
V.T.Doroshenko
I present results of my observations of Seyfert galaxy during 1986-2001 carried out with UBV photometer at 0.6-m telescope of Crimean Laboratory of Sternberg Astronomical Institute. UBV magnitudes show the strong changes during this period. I have analysed the lightcurves by computing the normalised power density spectrum and structure function.
09/27/01
Dottori Horacio Instituto de Física, Universidade Federal do Rio Grande do Sul
Av. Bento Gonçalves 9500, CP 15051
91501-970 Porto Alegre, Brasil
Presentation 1 : Poster
Circum-nuclear Structure in the Active galaxy NGC 1241
Diaz, R., Dottori, H, Villamizar, N., Carranza, G.
We study the spiral pattern in the inner 6.5 arcsec (1arcsec$\approx$265pc) of the Seyfert 2 nucleus of NGC1241. GEMINI-N K and J bands, as well as HST Pa_{$\alpha$} and (V+R) ones are analysed through 2-D and 1-D Fourier techniques. A small ($\approx$ 500 pc) long bar surrouded by a r=700pc ring, both emitting in Pa_{$\alpha$} are found. A CR at about r=350pc is also determined, which lead to a pattern speed of 230 km/sec. The NIR spiral structure is smoother than the optical one, as found in large scale patterns. Other interesting kinematical as well as morphological structures are discussed.
03/01/02
Dressel Linda Space Telescope Science Institute
3700 San Martin Drive
21218 Baltimore, MD, USA
Presentation 1 : Poster
A Search for Offset Black Holes in LINERs
L. Dressel
According to current theories of black hole formation and galaxy evolution, black holes and the AGN that they ignite do not necessarily lie at the center of the stellar distribution of their host galaxies. For example, galaxy mergers may result in binary black holes which move through the nucleus as they proceed toward coalescence. With the spatial resolution of WFPC2 and STIS on HST, it has become possible to search nearby galaxies on the scale of a few parsecs for offsets between the luminosity peak of the AGN, the luminosity peak of the stars, the kinematic center associated with the black hole, and the kinematic center of the stellar distribution. I will discuss the results of such a study of nearby bright LINER galaxies, and the instrumental effects which limit the ability to make such measurements.
08/28/01
Dultzin-Hacyan Deborah Instituto de Astronomia, UNAM, Mexico
Apdo 70-264, Ciudad Universitaria, Mexico D.F.
04510 Mexico D.F., Mexico
Presentation 1 : Poster
Environment and Host Galaxies of Active Galactic Nuclei
Deborah Dultzin-Hacyan, Yair Krongold & paolo Marziani
We have investigated the environment and host galaxies of Seyfert 1 & 2 galaxies, Narrow line Seyfert Galaxies, Bright IRAS galaxies and LINERs. The results will be presented
07/18/01
Dumont Anne-Marie observatoire de Paris-Meudon
5 Place J. Janssen
92195 Meudon, France
Presentation 1 : Poster
Modelling the spectrum of Active Galactic Nuclei: escape probabilities versus transfer computations
A-M.Dumont, S. Coup\'e, S. Collin, O. Godet
We compare different escape probability approximations commonly used for the line transfer, with full transfer computations made with the code TITAN designed for thick hot media. For several cases typical of the UV-X emitting region in AGN, we show that they can have a strong influence on the computed structure of the medium (temperature and ionization state), and consequently on the computed emitted spectrum in the soft X-ray range. We stress that the choice of the approximation is therefore important.
01/05/02
Duschl Wolfgang J. Institut fuer Theoretische Astrophysik
Tiergartenstr. 15
69121 Heidelberg, Germany
Presentation 1 : Poster
The Formation and Feeding of Massive Black Holes in the Early Universe
Wolfgang J. Duschl & Peter A. Strittmatter
It is still an open question whether the super-massive black holes thought to be present in quasars are of primordial nature, or whether there is a viable way of forming them in the very short time scale (less than a billion years) permitted by the observational data. In this contribution, we present a way in which a galaxy-galaxy merger can provide not only the ``fuel'' for quasar activity, but can also build a super-massive black hole, i.e., "the engine", in the first place.
02/28/02
El-Zant Amr University of Kentucky
Department of Physics and Astronomy, University of Kentucky, Lexington
50506 Lexingon, USA
Presentation 1 : Poster
Triaxial haloes and the formation of galaxies and their central regions
Amr El-Zant and Isaac Shlosman
Trajectories in slowly rotating triaxial systems with nearly constant density cores are self intersecting Lissageoux type figures (box orbits) which cannot support gas motion. This fact sets constraints on the manner a baryonic component settles in such a halo and the associated inflow of gas to the central region --- since a gaseous component can only find a stable state when its central concentration is suffcient so that the harmonic nature of the potential is broken and non-self-intersecting loop orbits can exist at all radii. We discuss the consequences of this phenomenon.
08/28/01
Elvis Martin Harvard-Smithsonian Center for Astrophysics
60 Garden St.
02138 Cambridge MA, USA
01/04/02
Emsellem Eric Centre de Recherche Astronomique de Lyon
9 avenue Charles Andre
69561 Saint Genis Laval Cedex, France
Presentation 1 : Oral
Fueling the nucleus via inner density waves
Eric Emsellem
Density waves in the central regions of galaxies, such as inner spirals, bars and/or lopsided density distributions are potential actors of the redistribution of angular momentum. They may thus play an important role in the overall evolution of the central structures, and in particular in the fueling of the nucleus, thus triggering an AGN and/or central starburst. I will present evidences for the importance of such structures using new sets of observations, including two-dimensional (OASIS/CFHT) and near-infrared long-slit (ISAAC/VLT) spectrography of active and non-active galaxies, with nuclear bars and spirals. I will also discuss the importance of (keplerian or not) m=1 modes in the nuclear regions of galaxies, illustrating this with new observations and original N body simulations. The implications of these observations/models will be discussed in the context of AGN, central starbursts and the nuclear dynamical evolution.
01/22/02
Everett John University of Chicago, Dept. of Astronomy & Astrophysics
5640 S. Ellis Avenue
60637 Chicago, IL, USA
03/01/02
Falcke Heino Max-Planck-Institut für Radioastronomie
Auf dem Hügel 69
53121 Bonn, Germany
Presentation 1 : Poster
Structure and Size of the Narrow-Line Region in Quasars
Heino Falcke, Nicola Bennert, Hartmut Schulz, Andrew S. Wilson, Beverley Wills
While structure and size of the narrow-line region (NLR) of Seyfert galaxies has been the subject of many detailed studies, surprisingly little is known about the NLR in quasars. We have therefore observed the NLR in a flux-limited sample of the seven brightest radio-quiet PG (or BQS) quasars (z lower than 0.5) with the WFPC2 camera onboard the Hubble Space Telescope. Linear ramp filters were used to image the [OIII] line emission with 0.1 arcsec resolution. We find that the NLRs have typical extents of only one-two arcseconds. A few quasars show compact filamentary structure known from Seyfert NLRs which are related to radio outflows. Most interestingly, we find that the size of the NLR seems to scale proportionally to the square root of the [OIII] luminosity. This is very similar to the scaling found for the broad-line region (BLR) which is explained in terms of a constant photoionization parameter. This relation seems to connect the NLR of radio-quiet quasars and Seyferts.
03/01/02
Fossati Giovanni Rice University
Physics and Astronomy Dept MS108, 6100 Main St.
77005-1892 Houston, Texas, USA
Presentation 1 : Poster
Assessing the influence of observational selection effects on unification schemes of AGNs
G. Fossati, C.M. Urry
In the framework of the continuing effort of identifying a viable unifying scheme for radio-loud AGNs we started a study to assess the role played by selection effects in shaping our knowledge. In fact, the interpretation of observed phenomenology depends on the complicated sensitivity of diverse surveys to a range of spectral types. The challenge is to work backwards, to determine intrinsic properties. Results from quantitative simulations suggest that intrinsically continuous distributions can be made to look bimodal simply because of these selection effects. We show that selection effects can strongly determine what "kind" of blazar comes out of what kind of sample, almost independently of the underlying distribution of spectral shapes. Indeed, with present data we can say remarkably little about the intrinsic spectral shapes (specifically, correlations between optical, radio, and X-ray bands) in blazars in known samples. For instance we show that the multiple flux selections typical of available surveys could induce some of the correlations found in color-color diagrams. These latter results should apply to any study of flux limited samples, in particular there is an interesting parallelism between the problem that we are studying for the blazar case and the much broader issue of the radio-loud vs. radio-quiet AGN dichotomy.
Presentation 2 : Poster
Physics with broad band spectral variability of MKN 421
G. Fossati et al.
We present the analysis of the 10-day RossiXTE observation performed in 2001, as part of the campaign with simultaneous TeV and optical observations. The source reached a flux of almost 1e-8 c.g.s. and the very high throughput allows us to probe the variability on very short timescales, i.e. down to a few minutes. Together with past BeppoSAX observations we now have a dataset covering an unprecedented range of timescales and fluxes, providing us with the best leverage ever to address the questions on the physical properties of this type of relativistic jet sources. We will discuss the main features of the timing analysis, from structure function and periodogram analyses, including tentative evidence of a recurrence timescale for major flares. This could possibly be interpreted as signature of some characteristic of the jet formation process, in the framework of the internal shock model, now revived also for blazars. Moreover we will present the extension -with the 2001 data- of the E_peak vs. L relationship, and a few highlights of the simultaneous TeV/Optical observations.
08/28/01
Fraix-Burnet Didier Laboratoire d'Astrophysique de Grenoble
BP 53
F-38041 Grenoble Cédex 9, France
Presentation 1 : Poster
Systematics and astrophysics : toward an evolutionary classification of galaxies.
D. Fraix-Burnet, P. Choler, E. Douzery
It is possible to borrow from a topic of biology called phylogenetic systematics, concepts and tools for a logical and objective classification of galaxies. It is based on observable properties of objects - characters - either qualitative (like morphology) or quantitative (like luminosity, mass or spectrum). Distance analysis can readily be performed using a method called phenetics and based on characters. But the most promising approach is cladistics. It makes use of characters that can exist in at least two states, one being "ancestral" and the other one "derived". Objects are gathered depending on the derived states they share. We illustrate a first application of this method to astrophysics, that we name "astrocladistics", with dwarf galaxies from the Local Group. Other groups of galaxies will be considered in the near future, the AGNs being undoubtly a target of choice.
02/27/02
Fruscione Antonella Chandra X-Ray Center
60 Garden Street
02138 Cambridge, USA
Presentation 1 : Poster
Catching NGC 4051 in the Low State with Chandra
Antonella Fruscione, Phil Uttley, Ian McHardy
For the past 5 years we have monitored the nearby Seyfert galaxy NGC 4051 with the Rossi X-ray Timing Explorer. Although usually highly variable, in early 1998 NGC 4051 entered into an unusual low-flux, low-variability state which lasted 5 months. A second 3-month-long low state followed in 1999. Simultaneous observations of NGC 4051 during the first low state by BeppoSAX and RXTE suggested that the central continuum source had completely switched off, leaving only the echo of X-ray reflection from distant cold material. To determine if any residual central continuum remains during the low states we were awarded a 50 ksec duration TOO with Chandra's ACIS-S, to be triggered if NGC 4051 entered the low state once more. Our target duly obliged in January and February 2001, and we present the results of the resulting TOO observation here, showing that the central, variable continuum does not go away during the low state, but mutates into a strange hybrid, very soft at low energies, and exceptionally hard at high energies.
03/01/02
Gabel Jack Catholic University of America
NASA's Goddard Space Flight Center
20771 Greenbelt, MD, USA
Presentation 1 : Poster
Intrinsic UV Absorption in the Seyfert 1 Galaxy NGC 3783 - FUSE and HST /STIS Results
Jack R. Gabel, D. Michael Crenshaw, Steven B. Kraemer, Team3783
We present results in the UV and far-UV, as part of an intensive multiwavelength monitoring campaign designed to study the intrinsic absorption in the Seyfert 1 galaxy, NGC 3783. We have combined 18 HST/STIS echelle grating observations and 5 FUSE observations to produce a high signal-to-noise averaged spectrum that samples numerous lines spanning a large range in ionization states. Analysis of the Lyman lines reveals a complex absorption geometry in the UV absorption. The individual covering factors of the continuum and broad line region emission sources are deconvolved. We find evidence for variable covering factor with velocity in the individual absorption components, with a decrease in the wings of the profiles. The H I covering factor profiles are used to derive ionic column densities for all available lines. These results are used to constrain the physical conditions in the absorbers and investigate the complex absorption geometry in NGC 3783.
12/17/01
Gallimore Jack Bucknell University
Department of Physics
17837 Lewisburg, PA, USA
Presentation 1 : Poster
NICMOS Observations of the Nuclear Star Cluster of NGC 1068
Jack F. Gallimore and Lynn Matthews
We have applied a PSF-fitting algorithm developed by John Krist(STScI) to analyze archival HST-NICMOS images of NGC 1068. We decomposed the central ~ 2 arcseconds into a bright, unresolved (point) source and a ~ 50 parsec diameter extended source. The point source has very red near-infrared colors, as expected for an AGN, but the extended source has colors matching those of an evolved, slightly reddened star cluster. Except for photometry, the properties of the cluster are compatible with the spectroscopic imaging results reported by Thatte et al. (1996). We consider the implications of the evolutionary stage of the cluster and present prospects of a more extended study of star clusters in Seyfert nuclei.
09/12/01
Gallo Luigi Max-Planck-Institut fur Extraterrestrische Physik
Postfach 1603
85741 Garching, Germany
Presentation 1 : Poster
An XMM-Newton Observation of the ULIRG Mrk 1014: An elusive soft X-ray component and evidence for a broadened Fe K line


Presentation 2 : Poster
HeI 5016 in the Narrow-Line Seyfert 1 Galaxy Akn 564

03/01/02
Garcia-Burillo Santiago OBSERVATORIO ASTRONOMICO NACIONAL
Alfonso XII, 3
28014 MADRID, SPAIN
Presentation 1 : Oral
NUclei of GAlaxies: The PdBure survey of nearby AGN hosts (NUGA)
S.Garcia-Burillo, F.Combes, A.Eckart, L.Tacconi, L.Hunt, S.Leon, A.Baker, P.Englmaier, F.Boone, E.Schinnerer, R.Neri
We present the first results of the NUclei of GAlaxies (NUGA) project. This is a combined effort to undertake a high resolution (1''-2'' ) and high-sensitivity CO survey, made with the Plateau de Bure IRAM interferometer, on a moderately large sample of 12 nearby AGN spirals, which span the whole sequence of activity types. We study the distribution and dynamics of molecular gas in the inner 1 kpc of the nuclei with resolutions of 30-100 pc, and analyse systematically the different mechanisms for gas fuelling of the AGN. The large variety of observed dynamical instabilities (m=1 modes, nuclear bars, spirals, warps,...) are interpreted with the help of N-body numerical simulations.
03/01/02
Giebels Berrie Lab Phys Nucleaire Haute Energie
Ecole Polytechnique
91128 Palaiseau Cedex, France
02/18/02
Giovannini Gabriele Astronomy Dept. - Bologna University
via Ranzani 1
40127 Bologna, Italy
Presentation 1 : Poster
Parsec Scale Properties of Low Power Active Galactic Nuclei
G. Giovannini et al.
There are several strong and widely accepted lines of evidences for the existence of relativistic bulk velocities in the parsec scale jets of radio sources. Moreover it became evident recently that relativistic jets are present in high and low power radio sources. Observational results imply similar jet velocities with a Lorentz factor in the range 3 -- 10 for radio galaxies, despite of the variety of their large scale morphology and different total radio power. I will show new VLBI observations of low power radio galaxies to confirm previous results that the nuclear emission at radio waves is largely dominated by relativistc radio jets also in low power radio galaxies, very similar to the situation in more luminous AGNs. A few interesting objects will be presented in detail. At the light of these results I will discuss if the observational differences between high and low power radio galaxies on the large scale could be due to a different interaction of parsec scale radio jets with the ISM in the nuclear regions.
12/04/01
Godet Olivier Centre d'Etude Spatiale du Rayonnement
9, avenue Colonel-Roche
31028 TOULOUSE, FRANCE
11/28/01
Gondoin Philippe European Space Agency
Keplerlaan 1, Noordwijk, The Netherlands
2200 AG Noordwijk, The Netherlands
Presentation 1 : Poster
XMM-Newton observation of the Seyfert 1 galaxy Mrk 335
P. Gondoin, A. Orr, D. Lumb, M. Santos-Lleo
We report on an XMM-Newton observation of the Seyfert 1 galaxy Mrk 335 performed in 2000 December. The 0.3--10 keV spectrum of Mrk 335 is compared with X-ray spectra of a sample of Seyfert 1 galaxies that we analysed within the frame of the XMM-Newton Guaranteed Time Programme. The spectral components of Mrk 335 exhibit important specificities, i.e (i) their luminosity is variable on timescales as short as a few ksec, (ii) the power law component above 2 keV has a photon index much steeper than that of a "normal" Seyfert 1 galaxy, (iii) the spectral feature observed around 6.0 keV is broad and can be fitted by a relativistic emission profile and (iv) the soft excess above the power law rises steeply below 2 keV and represents more than 30 % of the intrinsic source luminosity in the 0.3--2 keV band. We present a scenario that could account for these spectral properties taking into account previous ASCA and SAX observations.
Presentation 2 : Poster
Simultaneous XMM-Newton and BeppoSAX observation of the Seyfert I galaxy IC 4329A
P. Gondoin, P. Barr, D Lumb, T. Oosterbroek, A. Orr, A.N. Parmar
We report on a simultaneous XMM-Newton and BeppoSAX observation of the Seyfert 1 galaxy IC 4329A performed in 2001 January. Above 1 keV, EPIC spectra show a narrow Fe K emission line at 6.42 keV with an equivalent width of 43 eV. An absorption edge is detected at 7.1 keV in the source rest frame that has not been reported before. The energy of these features is consistent with reflection of the primary X-ray continuum by a optically thick material containing iron in low states of ionization. The narrow Fe K feature suggests that the reflection arises relatively far from a putative central black hole. Spectral fitting of simultaneous XMM-Newton and BeppoSAX data over the 0.3-130 keV energy range shows that the primary continuum is well described by a cut-off power law with a photon index of 1.93 and a folding energy of 260 keV. The high energy tail > 10 keV constrains the reflection fraction close to unity. Fitting over the overall spectral range indicates that the Fe abundance within the cool reflecting material is not significantly different from the cosmic value. The extrapolation of the primary power law continuum to energies < 1 keV indicates the presence of absorption edges produced by neutral and ionized oxygen. The optical depth of the O I edge at 0.54 keV constrains the intrinsic absorption by neutral material to an hydrogen column density of = 33 10^{20} cm^{-2} along the line of sight to IC 4329A nucleus. The energy of the edge at 0.854 keV is consistent with absorption by O VIII. A third edge at 0.660 keV is likely related to absorption by O VI and N VII. The simultaneous presence of O VI and O VIII edges without significant O VII absorption indicates that the warm absorber originates from at least two zones.
03/01/02
Griffiths Richard Carnegie Mellon University
Physics Dept., 5000 Forbes Ave.
PA 15213 Pittsburgh, USA
Presentation 1 : Poster
Iron line features in the spectra of NGC4151 and MCG-5-23-13
R.E.Griffiths, A.Ptak, N. Schurch, R. S. Warwick
We show that relativistically broadened iron line emission is not required to fit the X-ray spectra of NGC4151 and MCG-5-23-16 measured using the using the XMM-Newton observatory. The iron K-alpha line in each object is well fitted using a narrow Gaussian profile. Furthermore, we have searched for variability of the iron line without success, in contrast with variable line profiles found previously. We compare these results with those from MCG-6-30-15 and Mkn 766, and draw conclusions relating to the underlying geometries.
02/12/02
Groves Brent RSAA
Mt Stromlo Observatory, Cotter Rd, Weston
2611 ACT, Australia
Presentation 1 : Poster
Dust and Radiation Pressure in Narrow Line Regions
Brent Groves, Mike Dopita, Ralph Sutherland
The Spectra of Seyfert2 galaxies all show similar line emission, with less than 0.8 dex variation in line ratios like [OIII]5007/H-beta or [NII]6583/H-alpha. This tight clustering on line diagnostic diagrams has not been explained consistently by previous single component photoionisation models and has only been matched using more complex geometries. Here we put forward a new model of dusty, radiation-pressure dominated photoionised clouds which gives a physical explanation for the observed line ratios and for the tight clustering seen on line diagnostic diagrams.
09/19/01
Gurvits Leonid Joint Institute for VLBI in Europe (JIVE)
P.O.Box 2
7990 AA Dwingeloo, The Netherlands
Presentation 1 : Oral
Close look at the central engine of AGN with a VLBI magnifier
L.I.Gurvits
Very Long Baseline Interferometry (VLBI) with its new extension to the orbital radio telescope, VSOP/HALCA, offers an unrivaled angular resolution reaching milli- and sub-milliarcseconds at centi- and millimetre wavelengths. I will review recent results of VLBI studies of AGNs emphasizing the following: - nucleus-jet diagnostics based on VLBI, X- and gamma-ray observations of several high-redshift quasars (0014+813 and 2215+020 among them); - parsec- and sub-parsec-scale morphology in the brightest blazars known to date and several other ultra-compact radio-loud AGNs, including intra-day variable quasars; - statistical study of milliarcsecond structures in more than 500 AGNs, allowing us to estimate physical parameters in the optically thick regions of jets ("cores") and their relations to the central engine parameters.
02/27/02
Hall Patrick P. Universidad Catolica de Chile
Depto. Astronomia y Astrofisica, Casilla 306
22 Santiago, Chile
Presentation 1 : Poster
Unusual BAL Quasars from the Sloan Digital Sky Survey
Patrick Hall, Scott Anderson, Michael Strauss, Donald York et al.
The SDSS has confirmed the existence of populations of broad absorption line quasars with extreme properties. I will discuss the discovery of redshifted absorption troughs (confirmation of a rotating disk wind?), absorption from FeIII but not FeII (a very large column density of moderately ionized gas?), extremely reddened objects (extinction curves even steeper than that of the SMC), objects with overlapping troughs that remove 90% of the flux below MgII, and two mysterious objects which may or may not be unusual BALs. Implications of these objects for quasar and BAL outflow models will be discussed, along with preliminary results of various followup observations.
Presentation 2 : Poster
AGN from 2MASS
Patrick Hall
I present initial results of a survey for AGN from the 2-Micron All-Sky Survey. 2MASS can be used to select samples of AGN with a greatly reduced bias against dust-reddened or intrinsically red objects compared to optical surveys. Simple optical-NIR color criteria similar to those of Barkhouse & Hall (2001) have been used to select targets; spectroscopic followup shows that nearly 2/3 of K<13.5 candidates are AGN. Most are at z lower than 0.4, with some out to z=2 (2MASS can detect the most luminous quasars to z=4). The spectra show a wide range of continuum slopes, line widths and line strengths; I will discuss these and other properties of the sample.
09/12/01
Hamann Fred University of Florida
Department of Astronomy, 211 Bryant Space Science Center
32611-2055 Gainesville, FL, USA
Presentation 1 : Oral
Quasar Element Abundances as Probes of Host Galaxy Evolution
F. Hamann
The emission and absorption lines in quasar spectra provide measures of the gas-phase metal abundances at various locations in the host galaxies. The derived metallicities are typically near or several times above the solar value, indicating that quasars are preceded by, or coeval with, an episode of rapid and extensive star formation in the surrounding galactic (or proto-galactic) nuclei. These stars might be among the first to form in dense collapsed structures after the big bang. Chemical evolution models of these environments suggest that, to reach Z > Zo in well-mixed interstellar gas, the star formation must have begun > 0.1 Gyr before the observed quasar activity.
09/14/01
Henriksen Richard Queen's University at KIngston
Ontario Canada
K7L 3N6 Kingston, Canada
Presentation 1 : Poster
Nuclear Black Hole and Galaxy Symbiosis
Macmillan, Henriksen and Le Delliou
The question of how and when the massive black holes in the centres of galaxies are formed is studied in the context of the properties of galactic dark matter halos. We consider the effects of adiabatic growth of the black hole on various dark matter distribution functions and simultaneously the rate at which the black hole might grow due to the accretion of dark matter particles. Such a mechanism would allow the black hole to grow `invisibly' between the Quasar epoch and the present day. We also consider scenarios in which the nuclear black hole and the galaxy form together as this seems to be the best way in which to understand the black hole mass-galaxy velocity dispersion at large radii.
Presentation 2 : Poster
Relativistic Quadrupolar flow around a Schwarzschild Black Hole
RN Henriksen
The quadrupolar mechanism that has proved promising for explaining the molecular outflows around protostars, is generalized with a view to applying it to the gas flows observed in the nuclear regions of AGN, that is the narrow and broad lined regions.
08/29/01
Ho Luis Carnegie Observatories
813 Santa Barbara Street
91101 Pasadena, USA
Presentation 1 : Oral
The Central Engines of Low-Luminosity AGNs
Luis C. Ho
I will argue that nearby galaxy nuclei contain massive black holes that are fueled by low radiative efficiency accretion flows.
01/07/02
Hoyle Fiona Drexel University Department of Physics
3141 Chestnut Street
PA 19104 Philadelphia, USA
Presentation 1 : Poster
Using Large-Scale Structure to Probe the Physics of AGN
Fiona Hoyle and Michael Vogeley
Recent optical studies of AGN have revealed the unexpected result that the amplitude of clustering does not evolve with redshift. The likely dependence of AGN clustering on the host halo mass and heterogeneity in the events that trigger the efficiency of feeding the central engine imply that the observed clustering may strongly vary with wavelength and other selection criteria. However, progress on these issues has been limited by the small size of redshift samples of AGN selected at other than optical wavelengths. Here we describe a unique project that has recently obtained NASA funding that will combine X-ray, UV, IR and optically selected data to study the clustering of AGN. We will analyze samples of AGN detected in the X-ray band by the ROSAT, UV imaging and spectroscopy from the GALEX mission, IR imaging from SIRTF, together with results of the 2dF and SDSS QSO surveys. The spatial clustering of AGN reflects both the distribution of matter fluctuations in the universe and the complex non-linear astrophysics of black hole formation and feeding. The evolution of the AGN clustering amplitude is a crucial constraint on models of AGN, as this depends on the mass of the host halo at the epoch when the central engine shines brightly in the selection waveband. Precise measurements of AGN clustering as a function of parameters measured in multi wavebands will allow us to address key questions such as what are the lifetimes and environments of AGN? Are fluctuations in the X-ray background consistent with an AGN population? What is the power spectrum of mass, as traced by AGN, and does this evolve with redshift?
10/22/01
Hunt Leslie CAISMI-IRA/CNR
Largo E. Fermi 5
50125 Firenze, Italy
11/28/01
Hunt Matthew Caltech
Caltech 105-24
91125 Pasadena, CA, USA
Presentation 1 : Poster
Optically selected AGN at z ~ 3: Constraints on AGN fraction and the faint end of the luminosity function
M. Hunt, C. Steidel
I will present constraints on the AGN fraction and luminosity function at z ~ 3, based on the low-luminosity broad and narrow line AGN in our spectroscopic sample of Lyman break galaxies, perhaps also including medium-luminosity AGN in a 3 square degree survey to R < 23 to be conducted in the spring. These results will complement SDSS and other wide surveys which constrain the bright end of the luminosity function.
03/07/02
Huré Jean-Marc LUTh/Observatoire de Meudon & Université Paris 7
Place Jules Janssen
92195 Meudon, France
Presentation 1 : Oral
Self-gravity in AGN discs
J.-M. Huré
If there is a consensus that Active Nuclei are powered by accretion of gas onto a massive black hole, the structure and dynamics of the inflow remains poorly understood at the sub-parsec scale, not only in the hot, innermost region but also in the colder, outer ones. Our presentation will focus on these outer self-gravitating regions (beyond a few hundred Schwarzchild radii from the centre) where the disc mass, although relatively small, is expected to play a role, possibly dominant, on the disc evolution. Results derived from vertically averaged and vertically stratified disc models will be discussed. Some important consequences for the problem of AGN fueling will be mentioned.
12/13/01
Imanishi Masatoshi National Astronomical Observatory of Japan
2-21-1 Osawa
181-8588 Mitaka, Tokyo, Japan
Presentation 1 : Poster
Buried AGNs in LINER-Type Ultraluminous Infrared Galaxies
Masatoshi Imanishi, C. C. Dudley, and Philip R. Maloney
We report on 3--4 $\mu$m spectroscopy of ultraluminous infrared galaxies (ULIRGs). We aim to address the major issue of determining the relative energetic importance of AGN and star formation in ULIRGs, which becomes very difficult if the AGN is buried in a thick dust shell. At 3--4 $\mu$m, (1) buried AGN and starburst are distinguishable based on the 3.4 $\mu$m carbonaceous dust absorption and the 3.3 $\mu$m polycyclic aromatic hydrocarbon (PAH) emission, (2) dust extinction is as low as that at 7--8 $\mu$m, and (3) continuum determination, and thereby distinguishing between buried AGN and starburst, is much more secure than the 7.7 $\mu$m PAH-based energy diagnostic based on the {\it ISO} spectra. All of these advantages combine to make the 3--4 $\mu$m diagnostic a very powerful tool to detect ``buried'' AGNs and quantitatively estimate their energetic importance. We successfully find the evidence for energetically important buried AGNs in some ULIRGs classified optically as LINERs (40\% of ULIRGs). A theory also predicts that buried AGNs produce LINER-type optical spectra. We argue that, although LINER-type ULIRGs are currently taken to be starburst powered, a significant fraction of these ULIRGs could possess energetically important buried AGNs. This work has been published as Imanishi \& Dudley (2000 ApJ 545 701) and Imanishi, Dudley, \& Maloney (2001 ApJ 558 L93).
Presentation 2 : Poster
3--4 $\mu$m Spectroscopy of Seyfert 2 Nuclei to Quantitatively Assess the Energetic Importance of Compact Nuclear Starbursts
Masatoshi Imanishi
We report on 3--4 $\mu$m slit spectroscopy of 13 Seyfert 2 nuclei. The 3.3 $\mu$m polycyclic aromatic hydrocarbon (PAH) emission is used to estimate the magnitudes of compact nuclear starbursts ($<$ a few 100 pc), making use of two important advantages: (1) the uncertainty in dust extinction correction is smaller than shorter wavelengths (UV and optical), and (2) even weak starbursts are detectable. Based on our 3--4 $\mu$m slit spectra, we find that (1) except in one case, the observed nuclear 3--4 $\mu$m emission is dominated by AGN and not by starbursts, (2) compact nuclear starbursts are detected in 6 out of 13 Seyfert 2 nuclei, but cannot dominate the energetics of the galactic infrared dust emission in Seyfert 2 galaxies, and (3) more powerful AGNs tend to be related to more powerful compact nuclear starbursts, provided that the 12 $\mu$m luminosity measured with {\it IRAS} is a good measure of AGN power. This work will appear as Imanishi (2002, ApJ in press, astro-ph/0112299).
02/28/02
Inoue Makoto Nobeyama Radio Observatory
National Astronomical Observatory, Osawa 2-21-1
181-8588 Mitaka, Japan
10/29/01
Irwin Judith Queen's University
Dept. of Physics
K7L 3N6 Kingston, Canada
Presentation 1 : Poster
NGC~3079: A Spiral Galaxy with Double-Lobed Radio Emission
Judith Irwin Queen's University, Kingston, Canada, K7L 3N6 and D. J. Saikia National Centre for Radio Astrophysics, Pune University Campus, Post Bag 3, Pune, 411 007, India
NGC 3079 is unique amongst spiral galaxies in that it has a compact VLBI radio core as well as very well-defined radio lobes on kpc-scales. The radio emission has a double-lobed appearance (reminiscent of the more powerful ellipticals on much larger scales) and the lobes are clearly out of the plane in this edge-on system. Since there is also a nuclear starburst and a 'bubble' of H-alpha emission, this galaxy provides a nearby laboratory for the study of the relationship between AGNs and starbursts. We here present observations at 327 MHz and 610 MHz of this system using the new Giant Metre-Wave Radio Telescope in India, showing that the radio emission extends to much larger scales than previously observed. A comparison with selected images at other wavebands will also be presented.
09/13/01
Jackson Neal University of Manchester, Jodrell Bank Observatory
Lower Withington
SK11 9DL Macclesfield, Cheshire, UK
Presentation 1 : Poster
The central regions of Cygnus A
N. Jackson, C. Tadhunter, W.B. Sparks
Cygnus A is a key object; it is a powerful radio galaxy of radio luminosity similar to z~1 objects, but at a redshift of 0.06. We discuss HST imaging data in lines and continuum. Evidence is present for near-nuclear star formation in the central ~kpc. Determination of stellar ages will be very important in deriving constraints on the physics of the central regions of this canonical AGN. We also discuss the emission line characteristics of this source.
Presentation 2 : Poster
Dust and gas in 3C305
(order TBD): R. Beswick, A. Pedlar, N. Jackson, D. Axon, W.B. Sparks, J.P. Leahy, C. Mundell
3C305 is a nearby radio galaxy which shows strong warping of the stellar disk and a dust lane running almost parallel to the jet axis. We present and discuss HST and radio studies of the dust and gas which strongly constrain the geometry of this system, and explore the line ionization mechanism (photoionization/ jet-induced shocks) using emission line diagnostic ratios.
08/29/01
Jauncey David Australia Telescope National Facility, CSIRO
GPO Box 3023
2601 Canberra, ACT, AUSTRALIA
Presentation 1 : Poster
5 GHz VLA IDV survey of the northern sky
J.E.J. Lovell (1), D.L. Jauncey (1), H.E. Bignall (2), L. Kedziora-Chudczer (1), J-P Macquart (3), B.J. Rickett (4) and A.K. Tzioumis (1).
(1) Australia Telescope National Facility, CSIRO< Australia (2) Dept of Physics & Maths Physics, University of Adelaide, Australia (3) Kapteyn Astronomical Institute, Groningen, The Netherlands (4) University of California San Diego, USA.
We are undertaking an Intra-Day Variability (IDV) Survey of 700 flat-spectrum AGN with the VLA at 5 GHz. Current evidence supports interstellar scintillation (ISS) as the mechanism causing IDV at cm wavelengths. While the Survey is still underway, the first results show at least 15% of the sources exhibit IDV, and hence possess microarcsecond scale structure. There is also a strong flux density dependence on the fraction of IDV sources, and some indication that EGRET sources are more likely to exhibit IDV than non-EGRET sources.
03/02/02
Jogee Shardha California Institute of Technology
Astronomy Department, MS 105-24, 1200 East California Boulevard
CA 91125 Pasadena , USA
Presentation 1 : Oral
Bar-Driven Spiral Density Wave in NGC 5248: Implications for Central Activity
Shardha Jogee, Isaac Shlosman, Seppo Laine, Peter Englmaier, Johan H. Knapen, Nick Z. Scoville, and Christine D. Wilson
Through observations and modeling, we demonstrate how the recently discovered large-scale bar in NGC 5248 generates spiral structure that continues from 10 kpc down to 100 pc. Deep inside the bar, two massive CO spirals with streaming motions of 20--40 km/s cover nearly 180 deg in azimuth and connect to two narrow K-band spirals which delineate the super star clusters (SSCs) in a starburst ring at 375 pc. The data suggest that the K-band spirals are young, and the starburst has been triggered by a bar-driven spiral density wave (SDW). The SDW may even have propagated into the inner 90 pc where evidence of recent activity exists. We incorporate the effect of self-gravity in models of bar-driven gaseous SDW and find good agreement between the model and data. Thus study provides some of the best evidence to date for a strong dynamical coupling between the nuclear region and the surrounding disk. It suggests that a low central mass concentration, which may be common in late-type galaxies, is particularly favorable to the propagation of a bar-driven gaseous SDW deep into the central region of the galaxy, whereas a large central mass concentration favors other processes, such as the formation and decoupling of nuclear bars.
Presentation 2 : Poster
A Gas-Rich Starburst in an Advanced Merger Powering the ULIRG IRAS 17208
Shardha Jogee, Naveen Reddy, and Nick Scoville
The study of ultraluminous infrared galaxies (ULIRGs) in different evolutionary phases is central to probing the ULIRG-QSO connection and the formation of elliptical systems from the mergers of gas-rich spirals. Of particular interest is IRAS 17208-0014, a ULIRG which has a very high infrared luminosity (>10^{12} L_sun) and appears to be in an interesting merger phase. Extended optical tails suggest it is a merger of two high angular momentum disk systems. The merger is likely to be at an advanced phase given the presence of an r^{1/4} profile indicative of violent relaxation, and the detection of only one nucleus in NICMOS images. OVRO high resolution (1.0''x 0.7'') CO (2--1) observations, along with radio continuum, infrared, and optical data show a massive (several 10^{10} M_sun) concentration of cold molecular gas in the inner kpc, fuelling a starburst having a SFR of several 100 solar masses per year. The molecular ISM has scaled-up densities and linewidths in comparison with local starbursts. NICMOS images reveal bright central stellar clusters in the inner kpc region, reminiscent of super star clusters which are found in nearby starbursts and postulated to be proto-globular systems.
02/28/02
Kaastra Jelle SRON
Sorbonnelaan 2
3584 CA Utrecht, The Netherlands
Presentation 1 : Poster
One week with Chandra: a long look at NGC 5548
Jelle S. Kaastra, M. Crenshaw, I.M. George, A.C. Brinkman, D.A. Liedahl, S. Kraemer, F.B.S. Paerels, K.C. Steenbrugge, T.J. Turner, T. Yaqoob
We present the first results of a one week observation in January 2002 of the Seyfert 1 galaxy NGC 5548, using the Chandra low and high resolution grating spectrometers. The combined spectrum covers the entire 0.1-10 keV range with high resolution and unprecedented signal to noise ratio. Multiple velocity components and a range of at least two decades in ionisation parameter are discovered. A major outburst occured during this week long observation, and we obtained good spectra of the burst as well as of the pre- and postflare quiescent phase. Comparison of these spectra shows significant time variability in both resolved broadened emission components (up to velocities of 10000 km/s) as well as in the narrow absorption components. The implications in terms of both warm absorber and accretion disk will be discussed.
12/03/01
Kaiser Christian University of Southampton
Highfield
SO17 1BJ Southampton, England
Presentation 1 : Poster
Jets vs. cooling flows
C.R. Kaiser, M. Brueggen
The cooling flow paradigm for cluster of galaxies is coming under increasing pressure from observations failing to detect enough cooling gas. Here we present the results of analytical and numerical studies of how jets from AGN can heat and mix the cluster gas. Both effects drastically reduce the amount of cold gas deposited by the cooling flow thus bringing the theory of cooling flows in agreement with recent observations.
02/28/02
Kameno Seiji National Astronomical Observatory of Japan
2-21-1 Osawa, Mitaka
181-8588 Tokyo, Japan
Presentation 1 : Poster
Sub-pc-scale plasma tori around nuclei
Seiji Kameno, Satoko Sawada-Satoh, Makoto Inoue, Zhi-Qiang Shen, and Kiyoaki Wajima
We present evidence for plasma condensation in central sub-parsec region of AGN. Multi-frequency VSOP and VLBA observations towards radio-loud active galaxies unveil cold dense plasma which silhouettes against the background jet emission via thermal free-free absorption (FFA) process. Disk- or torus-like morphology of the absorber suggests the transition from the radial accretion to rotational accretion around the nucleus.
Presentation 2 : Poster
VSOP Observations of a Superluminal CSS Quasar 3C 380 - Evidence for a Swing of the Jet -
Seiji Kameno, Makoto Inoue, Kenta Fujisawa, Shen Zhi-Qinag, and Kiyoaki Wajima
We report VSOP observations toward a superluminal CSS quasar, 3C 380. Very straight ballistic motions of the knots are confirmed. We detected an emergence of a new knot component. The direction of the new knot with respect to the core is in p.a.=320 degree while other knots within 10 pc from the core align in p.a.=330 degree. We determined each epoch of ejection for each component based on a linear fit for the apparent motion, and found that the direction of the jet is approximately a sinusoidal function of the ejection epoch. This means that the nozzle of the jet is swinging.
11/02/01
Karas Vladimir Charles University Prague
Astronomical Institute, V Holesovickach 2
CZ-18000 Prague, Czech Republic
Presentation 1 : Poster
Star-disc interactions in galactic cores
Karas et al.
We present recent results in which long-term evolution of a dense nuclear cluster is investigated, taking into account dissipative action of interstellar environment. Starting from a spherical cluster surrounding a compact core we show how a flattened configuration is gradually developed on sub-parsec scale.
Presentation 2 : Poster
to be announced

02/28/02
Kaspi Shai Tel-Aviv University
School of Physics & Astronomy and the Wise Observatory
69978 Tel-Aviv, Israel
Presentation 1 : Poster
Reverberation mapping of high-redshift high-luminosity quasars
S. Kaspi
Reverberation mapping and black hole mass determination are currently available for AGNs with luminosity no greater than 10e46 ergs/sec. To further extend our knowledge of the most extreme cases we are undertaking a monitoring program of high-redshift (z=2 to 3.4) high luminosity (up to 10^48 erg/sec) quasars. Monthly photometric observations of 11 quasars, over a period of 7.5 years, and spectrophotometric monitoring of 8 of those objects, over 2.5 years, are now available. We will present preliminary results from this monitoring program which is aimed at measuring the most massive black holes in the universe.
12/06/01
Kawaguchi Toshihiro Department of Astronomy, Kyoto University
Sakyo-ku
606-8502 Kyoto, Japan
Presentation 1 : Poster
Electron Scattering in Slim Accretion Flows and Estimation of Age of Su permassive Black Holes
T. Kawaguchi
We examined the effects of electron scattering (opacity and^M Comptonization) on the emergent spectrum from slim accretion flows. ^M Then, the model is applied to Narrow-Line Seyfert 1 galaxys (NLS1s) ^M to estimate the accretion rates. We found that a NLS1,^M PG 1448+273, has an extremely large accretion rate in the unit ^M of Eddington luminosity (L_Edd); 1000 L_Edd/ c^2. This implys^M that the object is really young: its age ^M inferred from the black-hole mass divided by the accretion rate is ^M about 10^6 years.
10/22/01
Kazanas Demosthenes NASA/Goddard Space Flight Center
NASA/GSFC, Code 661
20771 Greenbelt, USA
Presentation 1 : Poster
Magnetorotational and Magnetoconvective Instabilities in Compressible Flows: A Study Through the Interchange Method
D. Kazanas, D. Christodoulou and J. Contopoulos
We obtain the general form of the axisymmetric stability criteria in a magnetized, compressible Couette flow using a variational principle, the so-called interchange method, which we applied successfully in the incompressible case in the past. This formulation accounts for the simultaneous presence of gravity, rotation, entropy and density gradients, a toroidal magnetic field and a weak axial magnetic field in its initial equilibrium state. The crucial aspect of the method is its explicit implementation of the relevant conservation laws in the computation of the ``free energy" of the system in its original equilibrium. As in the incompressilbe case, the presence of an axial field invalidates the conservation laws of angular momentum and azimuthal magnetic flux, introducing instead isorotation and axial current conservation along field lines. The stability criteria are therefore markedly different depending on whether an axial magnetic field is present. In limiting cases our formulation transparently recovers the convective and Parker instability criteria, as well as those of Newcomb and Terkovnikov pertaining to rotating magnetized plasmas derived through the implementation of much more laborious techniques.
09/04/01
Kewley Lisa Harvard-Smithsonian Center for Astrophysics (CfA)
MS-65, 60 Garden Street, Cambridge MA 02138
02138 Cambridge, MA, USA
Presentation 1 : Poster
The Starburst-AGN Connection in Infrared Merging Galaxies
Kewley, L.; Dopita, M.; Sutherland, R.
I will present new results in our study of the starburst-AGN connection in the central kiloparsec of a large sample of infrared galaxies. We have developed theoretical optical and infrared grids for determining the relative fraction of AGN to starburst emission in composite galaxies. These grids have been generated using a combination of detailed stellar population synthesis, photoionization and shock models. The optical AGN-starburst emission within the central kiloparsec has been found for our sample of merging infrared galaxies and is compared with indicators of merger evolution, including projected nuclear separation, and a morphological interaction type. We find that starburst activity is the dominant emission process in the initial stages of the merger. If an AGN exists, it becomes visible in the optical at intermediate stages of the merger. During the final stages of the merger, starburst activity is the dominant excitation mechanism. These results support an evolutionary scenario in which starburst activity is initially triggered by tidal interactions. As gas is funnelled towards the merger nucleus, an AGN is activated. Towards the final stages of the merger, circumnuclear starburst activity becomes the dominant excitation mechanism rather than the AGN.
12/12/01
Knapen Johan Isaac Newton Group and Univ. of Hertfordshire
Isaac Newton Group, Apartado 321
E-38700 Santa Cruz de La Palma, Spain
Presentation 1 : Oral
Morphology and structure of AGN hosts
J.H. Knapen
A number of mainly observational studies will be described which target the question whether the host galaxies of AGN are different than non-active galaxies, and whether these differences can lead us to understanding what initiates and fuels AGN activity. Studying matched samples of Seyfert and non-Seyfert galaxies, we have found that the Seyfert hosts are slightly, but significantly, more often barred than the non-Seyferts. Galactic interactions appear to have nothing at all to do with bar fractions. Both case studies and investigations of samples of galaxies clearly show how the circumnuclear regions of galaxies are intimately related dynamically to their host galaxies, most directly through their bars. Finally, characteristics of sub-kpc-scale features such as nuclear bars, spirals and rings and the role they may play in the AGN fuelling process will be considered.
03/02/02
Koenigl Arieh University of Chicago
Astronomy Dept., Univ. of Chicago, 5640 S. Ellis Ave.
60637 Chicago, IL, U.S.A.
Presentation 1 : Invited
Accretion Disk-Driven Outflows in AGNs
Arieh Koenigl
Analysis of spectral absorption features has led to the identification of several distinct outflow components in AGNs. The outflowing gas is evidently photoionized by the nuclear continuum source and most likely originates in the accretion flow toward the central black hole. The most likely driving mechanisms are line and continuum radiation pressure and magnetic stresses. The theoretical modeling of these outflows involves such issues as (1) Which of the above mechanisms actually contributes in each case? (2) How is the gas uplifted from the underlying accretion disk? (3) How can the intense central continuum radiation be shielded to allow efficient line driving? (4) Is the outflow continuous or clumped, and, if the latter applies, what is the nature and dynamical state of the ``clouds''? This review will summarize recent theoretical and observational results that bear on these questions and outline prospects for further progress in the field.
Presentation 2 : Poster
Analytical Modeling of Hydromagnetic Jets in AGNs
Nektarios Vlahakis and Arieh Koenigl
We use exact self-similar solutions of the steady, axisymmetric, relativistic, hydromagnetic equations to study the formation of AGN jets. Our formalism allows us to examine the effects of the thermal, centrifugal, and electromagnetic forces on the flow acceleration and collimation. We apply our analysis to the jet in NGC 6251 and show that the puzzling sub-pc scale acceleration to mildly relativistic speeds recently inferred in this source from VLBI measurements can be attributed to magnetic driving.
08/29/01
Kollatschny Wolfram Uni-Sternwarte
Geismarlandstr. 11
D 37083 Goettingen, Germany
Presentation 1 : Poster
BLR Kinematics in Mrk110
Kollatschny, w. et al.
We present line profile variations of the Balmer and He lines in Mrk110. The data have been taken with the 10m Hobby-Eberly telescope. We derive velocity-delay maps and discuss the kinematics in the BLR at radii of a few light days. Finally, we compare the results of this narrow line Seyfert 1 galaxy with those of other Seyfert galaxies.
02/12/02
Korista Kirk Department of Physics, Western Michigan University
1120 Everett Tower
49008-5252 Kalamazoo, MI, USA
02/27/02
Kotilainen Jari Tuorla Observatory
Vaisalantie 20
FIN-21500 Piikkio, Finland
Presentation 1 : Poster
The host galaxies of radio-loud and radio-quiet quasars at 1 < z < 2
J.K. Kotilainen, R. Falomo, A. Treves, M. Uslenghi
We report our study of the host galaxies and environment of quasars at redshifts 1 < z < 2. Deep high spatial resolution near-infrared imaging of 10 radio-loud and 8 radio-quiet quasars has been obtained with ISAAC on the ESO VLT. The properties of high z quasars are compared with those at lower z to explore the cosmological evolution of quasar host galaxies and their environment from z = 2 (close to the peak of quasar/galaxy formation) to z = 0. The quasar - host galaxy connection, the relevance of galaxy interactions for nuclear activity, and the implications of different host galaxy luminosities of the two quasar types for models of formation and evolution of quasars and galaxies are discussed.
Presentation 2 : Poster
Near-infrared spectroscopy of Seyfert and spiral galaxies
J.K. Kotilainen, J. Reunanen, M.A. Prieto
We present near-infrared long-slit spectroscopy of matched samples of nearby Seyfert and normal spiral galaxies. The central molecular content in Seyferts type 1 and 2 will be discussed in view of AGN unified models. The nuclear and radial stellar population content and star formation properties in the Seyferts and spirals will be compared. Finally, the link between nonstellar and stellar nuclear components, and implications for studies of active and non-active galaxies at higher redshift will be addressed.
01/09/02
Krause Martin Landessternwarte
Königstuhl
D-69117 Heidelberg, Germany
Presentation 1 : Poster
Hydrodynamic Simulations of Light Bipolar Large Scale Jets
Martin Krause and Max Camenzind
Emission line observations of high redshift (z>2) radio galaxies as well as recent Chandra X-ray observations at low redshift show interesting features around the symmetry plane of those objects. We have carried out simulations involving both jets, removing the artificial boundary condition at the symmetry plane. We use a low density contrast (IGM/jet approximately 10000) and take into account a decreasing density profile. We find that the jet bow shock undergoes two phases: First a nearly spherical one and second the well-known cigar-shaped one. We propose Cygnus A to be in a transition phase, showing currently clear signs from both phases. Due to inward growing of Kelvin Helmholtz instabilities between cocoon and shocked IGM, mass entrainment is observed predominantly in the symmetry plane. We propose this mechanism to produce emission line regions in high redshift radio galaxies, and maybe also the enigmatic X-ray features in the symmetry plane in Cygnus A.
08/31/01
Krishna Gopal National Centre for Radio Astrophysics (TIFR)
Post Bag No.3, Pune University Campus, Ganeshkhind Road
411 007 Pune, India
Presentation 1 : Invited
Radio Galaxies and the Star Formation History of the Universe
Gopal Krishna and P.J. Wiita
Multi-wavelength observations made in the last decade strongly suggest that the universe underwent an intense phase of star-formation in the past (z > 1). This intensive activity is commonly attributed to a higher galaxy merger rate when the universe was a fraction of its present age. After briefly reviewing these evidences, we examine the role of the powerful radio sources whose comoving density is known to be a few orders of magnitude higher at z ~ 2 ( the so called `quasar era'). Taking into account the most recent theoretical models for the temporal evolution of the size and luminosity of a powerful double radio source, as well as advanced Lambda-CDM simulations of the cosmic web of baryonic material at different redshifts, it is argued that during the quasar era a high fraction of the volume of the web was occupied by the lobes of double radio sources. Wide-spread compression of proto-stellar clouds, triggered by the high pressure of the synchrotron plasma of the radio lobes, can thus be expected to have played a significant role in the star formation history of the universe, and also in causing a rather high level of magnitization of the galactic and intergalactic material at early epochs.
02/22/02
Krongold Yair Instituto de Astronomia, UNAM
Inglaterra 137 A 301
04040 Mexico, Mexico
Presentation 1 : Poster
The Circum-Galactic Environment of Bright IRAS galaxies
Y. Krongold, D. Dultzin-Hacyan & P. Marziani
This paper studies systematically, for the first time, the circumgalactic environment of bright IRAS galaxies as defined by Soifer et al. (1989). While the role of gravitational interaction for luminous and ultraluminous IRAS galaxies has been well established by various studies, the situation is by far more obscure in the IR luminosity range of the bright IRAS sample, 10^{10}Lsol < Lfir < 10^{11} Lsol. To easily identify nearby companion galaxies, the bright IRAS sample was restricted to 87 objects with redshift range 0.008 < z < 0.018 and galactic latitude > 30^{o}. A control sample, selected from the Center for Astrophysics redshift survey catalogue, includes 90 objects matching the Bright IRAS sample for distribution of isophotal diameter, redshift, and morphological type. From a search of nearby companion galaxies within 250 Kpc on the second-generation Digitized Sky Survey (DSS-II), we found that the circumgalactic environment of the Bright IRAS galaxies contains more large companions than the galaxies in the optically selected control sample, and is similar to that of Seyfert 2 galaxies. We found a weak correlation over a wide range of far IR luminosity (10^9 Lsol < Lfir < 10^{12.5}Lsol) between projected separation and Lfir, which confirms a very close relationship between star formation rate of a galaxy and the strength of gravitational perturbations. We also find that the far IR colors depend on whether a source is isolated or interacting. Finally, we discuss the intrinsic difference and evolution expectations for the bright IRAS galaxies and the control sample, as well as the relationship between starbursting and active galaxies.
08/30/01
Lacy Mark Institute of Geophysics and Planetary Physics, LLNL/ UC Davis
L-413, LLNL, 7000 East Avenue,
94550 Livermore, USA
Presentation 1 : Poster
The production mechanism of radio jets in AGN and quasar grand unification
M. Lacy
Recent advances in estimating black hole masses in AGN show that radio luminosity is dependent upon black hole mass, accretion rate and a third parameter, probably black hole spin. We discuss the relative importance of these parameters, and indicate a scheme for unifying AGN on the basis of these three quantities, plus orientation.
02/24/02
Laor Ari Technion
Haifa
32000 Haifa, Israel
Presentation 1 : Poster
On the Evidence for Dust Sublimation and Condensation in AGN
Ari Laor
Ample evidence for dust in AGN is provided through its IR emission, extinction, and polarization. The innermost region where dust can survive against sublimation is just outside the BLR. Dust can strongly suppress line emission from photoionized gas, and it may thus provide a natural explanation for the typical extent of the BLR, R_BLR, and its luminosity dependence (Laor \& Draine; Netzer \& Laor). This suggestion can be further tested by looking for the unique signature of dust sublimation and condensation in AGN. Variations in the AGN optical to X-ray continuum, L, produce corresponding variations in the dust sublimation radius, R_sub, and should thus produce matching variations in R_BLR. Dust sublimation is practically instantaneous, while dust condensation can take ~year at typical BLR densities. Thus, there should be an hysteresis effect in the R_BLR vs. L relation in a given object. R_BLR should closely track L when both increase, but there should be a long delay in the drop of R_BLR when L decreases rapidly. Hysteresis of an opposite nature should be present in the response of the 3mic emission to variations in L. This talk will present some quantitative predictions of dust sublimation and condensation effects, together with some possible existing observational hints for these effects.
Presentation 2 : Poster
The Quasar Continuity Equation
Ari Laor
Quasars form, evolve, and die. Applying the continuity equation to the observed time evolution of the quasar luminosity function allows, under some assumptions, to relate the quasar formation rate to the luminosity evolution rate. Applications to some recent luminosity function measurements will be presented.
09/05/01
Lasota Jean-Pierre IAP Institute of Astrophysics
98b Bd Arago
75014 Paris, France
Presentation 1 : Panel
12/20/01
Lawrence Andy Institute for Astronomy, University of Edinburgh
Royal Observatory, Blackford Hill
EH9 3HJ Edinburgh, Scotland, UK
Presentation 1 : Oral
The Ghost in the Machine
A.Lawrence
I summarise evidence and new calculations confirming that the Big Blue Bump is thermal, and that variations are caused by heating. There is however a serious energy budget problem, and various other correlations and non-correlations are inconsistent with this picture. I suggest ways in which some radical thinking aboiut how energy emerges from a black hole may solve this dilemma.
03/02/02
Leighly Karen The University of Oklahoma
Department of Physics and Astronomy, 440 W. Brooks St.
73019 Norman, OK, USA
Presentation 1 : Poster
Chandra HETG Observation of the Ultrasoft Narrow-line Seyfert 1 Galaxy 1H0707-495
Karen M. Leighly, Andrzej A. Zdziarski, Toshihiro Kawaguchi, Chiho Matsumoto
A Chandra observation of the ultrasoft Narrow-line Seyfert 1 galaxy 1H0707-495 using the HETG spectrometer reveals a strong soft excess, a weak power law, and absorption near 1 keV that may be the direct result of the strong soft excess. We observed strong spectral variability in which the soft component varied much less than the hard component, a behavior that is both quite suggestive of soft-state X-ray binaries, and in contrast to the colorless variability of other NLS1s observed by Chandra and XMM-Newton. 1H 0707-495 was bright when we observed it, and a comparison of historical observations reveals suggestively bimodal behavior. We interpret this bimodality as the signature of the radiation pressure instability, and suggest that this instability may be expected in this object, resulting from a high accretion rate, and lack of strong corona that could stabilize the accretion disk.
Presentation 2 : Poster
FUSE Observation of the Narrow-line Seyfert 1 Galaxy RE 1034+39
Darrin Casebeer and Karen M. Leighly
It has long been thought that the shape of the ionizing continuum of an Active Galactic Nucleus (AGN) should influence their broad emission lines. We made multiwavelength observations of RE 1034+39, an object with an unusual spectral energy distribution that is strongly peaked in soft X-rays. We report detailed analysis of the FUSE spectrum as well as a reanalysis of the HST spectrum. We present a model using the photoionization code Cloudy for the emission lines in this object, and discuss the results of a general systematic search for emission lines sensitive to the shape of the spectral energy distribution.
02/06/02
Leon Stephane I. Physikalisches Institut, University of Cologne
77, Zulpicher Str.
50937 Cologne, Germany
Presentation 1 : Poster
Molecular gas in nearby powerful radio galaxies
S. Leon, J. Lim, F. Combes, Dinh-V-Trung
We report the detection of CO(1-0) and CO(2-1) emission from the central region of nearby 3CR radio galaxies(z$<$0.03). Out of 21 galaxies, 8 have been detected in, at least, one of the two CO transitions. The total molecular gas content is below 10$^9$ \msun. Their individual CO emission exhibit, for 5 cases, a double-horned line profile that is characteristic of a disk with a central depression at the rising part of its rotation cu or ring distributions of the molecular gas is consistent with the ob dust disks or rings detected optically in the cores of the galaxies. their gas originates from the mergers of two gas-rich disk galaxies, explain the molecular gas in other radio galaxies, then these galaxie long time ago (few Gyr or more) but their remnant elliptical galaxies (last 10$^7$ years or less) become active radio galaxies. Instead, we cannibalism of gas-rich galaxies provide a simpler explanation for th molecular gas in the elliptical hosts of radio galaxies (Lim et al. 2 Given the transient nature of their observed disturbances, these gala active in radio soon after the accretion event when sufficient molecu in their nuclei.
Presentation 2 : Poster
Nuclear starburst, outflows and molecular gas in the LINER galaxy NGC6764
S. Leon, A. Eckart
TBA-
02/26/02
Levenson Nancy University of Kentucky
Department of Physics and Astronomy
40506-0055 Lexington, KY, USA
Presentation 1 : Poster
The X-ray Effects of Starbursts in Active Galaxies
N. A. Levenson, K. A. Weaver, and T. M. Heckman
Circumnuclear starbursts are common in Seyfert 2 galaxies, producing distinct X-ray signatures. As we demonstrate with new Chandra observations of starburst/AGN composite galaxies, stellar processes generate significant soft X-ray emission. The AGN are more important at higher energies, and they tend to be heavily obscured, by N_H > 10^{24} cm^{-2}. Their Fe line emission is prominent, with equivalent widths up to 9 keV, which constrains the geometry of the obscuring medium. Composite galaxies tend to have large covering fractions, an effect likely due to energy input from the starburst, which inflates the obscuring torus. Composite galaxies in general therefore present few direct lines of sight to their central engines, effectively hiding their intrinsically bright X-ray continua.
02/28/02
Lim Jeremy Academia Sinica Institute of Astronomy & Astrophysics
Po Box 232-141
106 Taipei, Taiwan
Presentation 1 : Poster
Molecular Gas Reservoir in low-z Powerful Radio Galaxies
Jeremy Lim, Stephane Leon, Francoise Combes, & Dinh-V-Trung
Classical double-lobed radio galaxies are hosted almost exclusively by elliptical galaxies that otherwise resemble normal elliptical galaxies in both their global stellar distribution and kinematics. Given that normal elliptical galaxies usually contain undetectable quantities of neutral gas, what fuels the AGN in powerful elliptical radio galaxies? Here, we present results of a search for molecular gas in radio galaxies at z < 0.031 selected from the revised 3C catalog, comprising the most powerful radio galaxies in the Local Universe. We detected 4 of the 22 galaxies observed, with molecular gas masses ranging from about 10^7-10^9 Msun; the remaining galaxies were not detected at a typical upper limit of about 10^8 Msun. We argue that this molecular gas most likely originates from the cannibalism of secondary gas-rich galaxies by the parent elliptical galaxy, rather than the merger of two gas-rich galaxies that spawned a remnant elliptical galaxy. All the galaxies detected possess central dust disks or lanes, and exhibit very broad double-horned line profiles characteristic of a rapidly-rotating disk with an inner depression. We suggest that this molecular-gas disk comprises the gas reservoir for fueling the central supermassive black hole. Finally, we present preliminary results of a follow-up survey to better understand the mass distribution of molecular gas in powerful radio galaxies. The results thus far show that an increasing number of radio galaxies become detectable in molecular gas at lower mass limits, suggesting a broad (at least 3 orders of magnitude) distribution of molecular gas masses in powerful radio galaxies.
12/18/01
Lister Matthew National Radio Astronomy Observatory
520 Edgemont Road
22903 Charlottesville, USA
Presentation 1 : Poster
Kinematics of Relativistic Jets in Active Galactic Nuclei: The 2cm VLBA Survey
M.L. Lister
We discuss an ongoing Very Long Baseline Array program to investigate the kinematics of relativistic jets in the brightest, most compact active galactic nuclei in the northern sky. Since 1994 we have taken more than 800 images with submilliarcsecond resolution and have measured accurate motions for 100 sources. We present an overview of the diversity of kinematics including non-radial accelerations, jet bending, and the distribution of apparent jet speeds. A major goal of our study is to test the predictions of the relativistic beaming model and unified schemes by looking for correlations between jet kinematics and other source properties such as multi-wavelength luminosity, variability, and radio morphology.
02/18/02
Lodato Giuseppe Scuola Normale Superiore
Piazza dei Cavalieri, 7
56126 Pisa, Italy
Presentation 1 : Poster
Non-Keplerian rotation in AGNs
G. Lodato & G. Bertin
There is now growing observational evidence for the presence of accretion disks in the nuclei of active galaxies. In some cases, the outer regions of these disks can now be directly imaged and their rotation traced with water maser spectroscopic observations. In standard \alpha-models the value of the axisymmetric stability parameter Q would decrease rapidly with increasing radius, and eventually become much smaller than unity. This proves that the self-gravity of the disk should modify the relevant physical processes in the outer disk regions, where non-self-gravitating models are thus expected to fail. Here we illustrate a simple, steady-state model for a self-gravitating accretion disk, marginally stable with respect to axisymmetric Jeans instability. This model is characterized by a rotation curve which is flatter than Keplerian in the outer disk. The modified energy balance needed to bring the disk to a self-regulated state makes self-regulated disks thermally stable, even when optically thin bremsstrahlung is the dominant cooling term. Observations of the disk rotation in some Seyfert galaxy nuclei, such as that of NGC 1068, often show deviations from the Keplerian regime. Here we provide an interpretation of the observed kinematical properties of these objects in terms of our self-gravitating disk models. An interesting consequence is a quantitative estimate of the value of the long-sought parameter \alpha.
11/20/01
Macchetto F. Duccio Space Telescope Science Institute
3700 San Martin Drive
MD 21218 Baltimore, MD 21218, USA
Presentation 1 : Oral
Supermassive Black Holes in Seyfert Galaxies
Macchetto, Capetti, Axon, Marconi
We have carried out a number of observations of the nuclear regions of Seyfert galaxies using the STIS spectrograph on board the HST, and a number of spectrographs at different ground based telescopes. For each of these galaxies we have measured the rotation curve and determined the mass distribution within 5-50 pc. We have modeled the stellar mass component using existing HST images and we have derived the masses of the black holes in each galaxy. The questions that we address are: what is the typical mass of the balck hole in Seyfert galaxies? Are Seyfert galaxies scaled down versions of QSOs or are they relics, accreting at a low rate? How do the black hole masses of Seyfert 1 compared with those of Seyfert 2? How do our result compare with those obtained with the reverberation mapping technique, which is however limited to Seyfert 1 galaxies? These results will be very important in clarifying the role of the black hole in powering the AGN, will shed light into the effectiveness of the accretion and finally will be important in addressing the fundamental issue of unification for Seyfert 1 and 2.
02/26/02
Macquart Jean-Pierre Kapteyn Institute
Kapteyn Institute, University of Groningen, Postbus 800
9700 AV Groningen, The Netherlands
Presentation 1 : Poster
The microarcsecond properties of J1819+385
Macquart, de Bruyn, Dennett-Thorpe
With intensity modulations >30% on a timescale less than 0.5 hr, the quasar J1819+385 is the most extreme variable intra-day variable radio source known. This source continues to show very high modulations, indicating a lack of expansion (v/c < 0.1). This is puzzling in light of the brightness temperature, well in excess of 10^12 K. Annual modulations in the variability timescale, combined with a direct measurement of the scintillation speed, indicate that the scintillation pattern of this source is highly elongated. This is either due to an elongated source and/or anisotropic scattering. Furthermore, comparison of the 3 and 6 cm lightcurves indicates the source is comprised of at least two distinct components. Short-timescale structure is observed in the 21 cm lightcurves which, if real, indicates diffractive scintillation from an extremely compact region of the source. The source also exhibits polarization variations, showing that a portion of the source is linearly and circularly(?) polarized on microarcsecond scales. This information is assembled into a coherent picture of the source.
03/05/01
Maiolino Roberto Osservatorio Astrofisico di Arcetri
Largo E. Fermi 5
50125 Firenze, ITALY
Presentation 1 : Invited
ELUSIVE AGN IN STARBURST and NORMAL GALAXIES
R. Maiolino
A fraction of galactic nuclei which are optically classified as starburst or as "normal" nuclei show indications for the presence of a powerful AGN when observed in the X-rays, in the infrared or in the radio. I will discuss these evidences obtained from past and new observations and suggest that these galaxies are probably hosting AGN which are obscured in all directions and, therefore, do not produce the AGN signatures typically observed in the optical. An important implication of these findings is that optical surveys have probably underestimated the fraction of AGN hosted in starburst and normal galaxies in the local universe. I will also discuss important implications on the starburst-AGN connection and, in particular, the relation between AGN obscuration, starburst activity and non axisymmetric morphologies of the host galaxies.
03/05/01
Maraschi Laura Osservatorio Astrofisico di Brera
via Celoria 16
I-20133 Milano, ITALY
Presentation 1 : Invited
From Blazar Radiation Mechanisms to Physical Parameters of Jets and the Jet - Disk connection.
I will briefly review the basic modelling of the Spectral Energy Distributions of blazars leading to an understanding of their systematic properties as determined by the total power carried by the jet. The findings for the blazar emission region (subparsec scale) can in some cases be compared with the physical parameters estimated from the outer X-ray emitting regions resolved by CHANDRA (kpc scale or larger) yielding a consistent picture of the jet propagation. Moreover the analysis indicates that for Flat Spectrum Radio Quasars the total jet luminosity is of the same order as the accretion luminosity, while for BL Lac objects the jet luminosity is larger than the disk luminosity. This can be understood within a unified scenario for FSRQs and BL Lacs if the jet production mechanism in both classes is similar, but the accretion rate is near critical in FSRQs and largely subcritical in BL Lacs. As a consequence the central black hole masses should be large in both cases. The different morphologies of FRI and FRII radio galaxies find a natural explanation in the context of the lower pressures estimated for BL Lac jets (FRI)
10/28/01
Marco Olivier European Southern Observatory, Chile
Casilla 19001, Alonso de Cordova 3107, Vitacura
19 Santiago, CHILE
Presentation 1 : Poster
Studying AGN from the central engine to the host galaxy: how adaptive optics systems can help.
Marco, O.
In this presentation, we will review the published results obtained with Adaptive Optics systems in the study of AGN, from the surroundings of the central engine to circumnuclear starbursts. Based on this review, prospects for the future, using the new available systems on giants telescopes will be discussed.
Presentation 2 : Poster
The PAH contribution to AGN near-infrared emission.
Marco O., Brooks K.
In the course of building ``unified models'' of Active Galactic Nuclei, the near infrared emission in the central kilo-parsec nuclear region is a key parameter: this wavelength range corresponds to the hot to warm dust emission, which originates in the torus and the Narrow Line Region (from a few parsecs to hundreds of parsecs). The measured flux is interpreted in terms of thermal emission and, via a dust modelisation, torus models are built. Using ISAAC at VLT, we observed a sample of AGNs in order to estimate the relative contribution between the thermal continuum emission from silicate & graphite dust grains and PAH molecules.
09/04/01
Marconi Alessandro Osservatorio Astrofisico di Arcetri
Largo E. Fermi 5
I-50125 Firenze, Italy
Presentation 1 : Poster
Searching for Supermassive Black Holes in Active Galactic Nuclei: the Near Infrared Domain
A. Marconi
During the past few years observations from the Hubble Space Telescope have produced a breakthrough in our knowledge on Supermassive Black Holes in nearby galaxy nuclei. However observations have been limited to unobscured, nearby objects because HST is a "small" telescope and lacks a near infrared spectrograph. I will present present preliminary results from two ongoing programs which plan to extend our knowledge on Black Holes in galactic nuclei by means of near infrared spectroscopy with ISAAC at the ESO Very Large Telescope: one program is aimed at detecting Black Holes in dust obscured active galactic nuclei and the other is aimed at measuring black hole masses in high redshift (z~2) quasars.
02/04/02
Marshall Herman MIT Center for Space Research
Rm NE80-6031, 77 Massachusetts Ave.
MA 02139 Cambridge, USA
Presentation 1 : Poster
Comparing High Resolution X-ray Spectra of Active Galaxies
Herman L. Marshall, Claude R. Canizares, and Julia Lee
MIT Center for Space Research
The High and Low Energy Transmission Grating Spectrometers on the Chandra X-ray Observatory have been used to obtain high spectral resolution with very good signal for over two dozen active galaxies. Spectral features have been found in each of four primary classes: blazars, Sy 2, Sy 1, and narrow line Sy 1 (NLS1) galaxies, ranging from narrow emission lines from local ionized gas to absorption by the intergalactic medium (IGM). The soft X-ray spectra of several Sy 2 galaxies consist of weak continua with emission lines indicative of photoexcitation by the nuclear X-ray source. This soft X-ray emission is often extended and generally matches any extended narrow line region. The Sy 1 and Sy 2 spectra are generally consistent with unification models involving a thick neutral absorber. Most blazars and only one NLS1 have remarkably featureless spectra. These featureless spectra have been used to detect or place limits on absorption by the ionized gas in the Galactic halo or the IGM. This work has been supported in part by NASA contract NAS8-39073 to the Chandra X-ray Center.
08/30/01
Marquez Isabel Instituto de Astrofisica de Andalucia
Apdo 3004
18080 Granada, Spain
09/26/01
Martin Jean-Michel Observatoire de Paris-Meudon-Nançay, GEPI
place Jules Janssen
F-92190 Meudon, France
01/18/02
Martini Paul Carnegie Observatories
813 Santa Barbara St.
91101 Pasadena, CA, USA
Presentation 1 : Poster
Circumnuclear dust in active and nonactive galaxies: Implications for AGN fueling and their duty cycle.
Paul Martini (OCIW), Michael W. Regan (STScI), John S. Mulchaey (OCIW), and Richard W. Pogge (Ohio State)
We have completed a visible and near-infrared HST survey of 123 nearby active and nonactive galaxies. The goal of this program is to study the cold ISM in the circumnuclear (less than a kiloparsec) region and search for AGN fueling mechanisms. These observations show that nuclear dust spirals exist in the majority of spirals, independent of the presence of an active nucleus. The morphology of the nuclear spiral structure is instead more closely connected to the presence of a large scale bar. Dust lanes along the leading edges of bars become grand design nuclear dust spirals in the circumnuclear region and demonstrate the inflow of matter over many kiloparsecs. Well-matched samples of active and nonactive galaxies show only marginal differences in their circumnuclear dust morphologies on scales as small as a hundred parsecs. We discuss the implications of these similarities for the transfer of angular momentum and how they provide an upper limit on the AGN duty cycle.
10/08/01
Marziani P. Osservatorio Astronomico di Padova
Vicolo dell'Osservatorio 5
I-35122 PADOVA, ITALIA
Presentation 1 : Poster
Broad Line Region Structure Along the Eigenvector 1 Sequence
P. Marziani, R. Zamanov, J. W. Sulentic, et al.
We present here the general results from the analysis of spectroscopic observations of 180 AGN. We have considered the spectral region of H-beta and measured FeII, HeII 4686 and H-beta line parameters. Along the so-called Eigenvector 1 sequence (correlation between H-beta broad component width and W(FeII4570)/W(H-beta)) we see that there are clear trends as far as the line profile of the broad component of H-beta is concerned. We discuss the implications of these trends for broad line region models. We also consider the CIV 1549 line as a diagnostic of a high ionization wind. We show that the possibility of having two decoupled regions, namely one emitting low-ionization lines and one emitting high-ionization lines, depends on the AGN location in the Eigenvector 1 sequence. Finally, we discuss the occurrence of a very broad component that may be associated to an optically thin, innermost "very broad line region."
Presentation 2 : Poster
The Relationship Between BAL QSOs and the General Population of AGN
P. Marziani, R. Zamanov, Ch. Bongardo, et al.
We have been compiling an atlas of Broad Absorption Line AGN at low redshift following a relatively broad criterion. The UV absorption properties have been associated, whenever possible, to the location in the so-called Eigenvector 1 diagram (sensitive to orientation and Eddington ratio), and to other optical UV and X-ray properties as well. We discuss whether BAL AGN are ``every quasar's sidelook" or whether a minimum Eddington ratio is necessary for the occurrence of BALs.
12/17/01
Masnou Jean-Louis Observatoire, Université Bordeaux 1
1 rue Pierre Sémirot
33270 FLOIRAC, FRANCE
02/25/02
Matt Giorgio Dip. Fisica, Universita' Roma Tre
via della Vasca Navale 84
I-00146 Roma, Italy
Presentation 1 : Oral
Changing face: from Compton-thick to Compton-thin (or viceversa)
Giorgio Matt and Matteo Guainazzi
A few X-ray obscured AGN have changed their appearance from Compton-thick, i.e. reflection-dominated, to Compton-thin (or viceversa) on time scales of a few years. A recent example is UGC4203, clearly a Compton-thin source during the XMM-Newton observation but reflection-dominated a few years earlier, when observed by ASCA. Here, besides presenting the most recent observational results, we discuss possible interpretations of this effect, and the implications for the Unification Model of Seyfert galaxies.
02/28/02
McHardy Ian University of Southampton
Department of Physics and Astronomy, University Road
SO17 1BJ Southampton, UK
Presentation 1 : Poster
X-ray Variability of AGN: The Galactic - Extragalactic connection
Ian McHardy, Phil Uttley, Georg Lamer, Keith Mason, Matt Page
We present the results of 6 years of intensive monitoring on ~few daily timescales of a sample of AGN with RXTE together with, in some cases, continuous ~few hundred ksec observations with ASCA and XMM. These observations provide the best data so far obtained on the long and short timescale X-ray variability of AGN and, via their powerspectra (PSDs), enable us to compare AGN with galactic black hole candidates (GBHs). The XMM observations probe shorter timescales than ever before and, in NGC4051, show steepening of the PSD at ~few hundred sec to a slope of -2.7, thereby removing previous fears that mass-energy conversion efficiency might exceed 40%. In some cases AGN PSDs are more similar to those of `high' than `low' state GBHs. The XMM observations also clearly show a hardening of high frequency PSD slope with increasing photon energy, as seen in GBHs and commonly described by Comptonisation models. We compare the AGN black hole masses derived from reverberation studies with those derived by comparing AGN PSDs, in high and low state models, with those of GBHs.
Presentation 2 : Poster
Long Timescale X-ray Spectral Variability of AGN
Ian McHardy, Georg Lamer, Phil Uttley
We summarise the X-ray spectral variations seen in 6 years of monitoring of a sample of AGN with RXTE. All AGN show a steepening of the spectra with increasing continuum flux, reaching a constant saturation level at high continuum fluxes (eg Lamer et al 2000). In at least one case (NGC4051) we can place limits on the flat spectrum, constant, reflected contribution from the torus. We can then show that the steepening is not the result of diluting a variable steep spectrum component with a constant hard torus component, although other locations for a hard component may be possible. We also note that the iron line flux does not change greatly with continuum flux although, at the highest continuum fluxes, there may be signs of an increase in iron line flux. We discuss possible reasons for these observations.
02/28/02
Merloni Andrea Max Planck Institut fur Astrophysik
Karl Schwarschild Str. 1
D-85741 Garching, Germany
Presentation 1 : Poster
The physics of magnetic accretion disc coronae: spectral variability and compact jets
A. Merloni, A.C. Fabian
Accretion disc coronae are believed to be the site where most of the X-ray emission from AGN is produced. We discuss how magnetic fields in the accretion flow generate and energize the coronae, and show how to use the observed spectral and temporal variability of AGN to gain insight on the physical and geometrical properties of such coronae. Finally, we discuss why powerful coronae in systems accreting at low rates should be the ideal sites for launching outflows, thus furhter reducing the observed bolometric luminosity in these systems. Such a scenario may be relevant to low luminosity AGN and have consequences for our understanding of the accretion history of the universe.
02/24/02
Merritt David Rutgers University
Department of Physics and Astronomy, 136 Frelinghuysen Road
08854 Piscataway, NJ, USA
Presentation 1 : Invited
Dynamical Effects of Black Holes on Host Galaxies
David Merritt
The addition of mass concentrations like supermassive black holes to the centers of stellar systems is usually assumed to increase the central density. If mergers are taken into account, the effect is the opposite: decay of the binary that forms during the merger transfers energy into the background and lowers its density. Results of N-body simulations and analytic treatments of this process will be discussed, with applications to stellar nuclei and to dark-matter cusps.
Presentation 2 : Poster
Black Hole Mergers: A Smoking Gun?
D. Merritt and R. D. Ekers
We present observational evidence for the coalescence of supermassive black holes and compute the event rate.
08/28/01
Mirabel Felix Service d'astrophysique. CEA/Saclay.
Bat 709. L'Horme des Merisiers.
91191 Gif/Yvette, France
Presentation 1 : Oral
Ultraluminous Galaxies and AGNs
I.F. Mirabel
I will review our knowledge on ultraluminous galaxies with particular emphasis on the connection between nuclear starbursts and feeding mechanisms in AGNs.
02/28/02
Morales Raquel Harvard-Smithsonian Center for Astrophysics
60 Garden Street, MS 29
MA 02138 Cambridge, USA
Presentation 1 : Poster
Weighing black holes with warm absorbers
R. Morales and A.C. Fabian
We present a new technique for determining an upper limit for the mass of the black hole in active galactic nuclei showing warm absorption features. The method relies on the balance of radiative and gravitational forces acting on outflowing warm absorber clouds.It has been applied to 6 objects: five Seyfert 1 galaxies: IC4329a, MCG-6-30-15, NGC 3516, NGC 4051 and NGC 5548; and oneradio-quiet quasar: MR 2251-178. We discuss our result incomparison with other methods. The procedure could also be applied to any other radiatively driven optically thin outflow inwhich the spectral band covering the major absorption is directlyobserved.
Presentation 2 : Poster
A comparative View of the Warm Absorbers/Emitters observed with the Chandra High Resolution Gratings
R. Morales, F. Nicastro and M. Elvis
We present preliminary results from a systematic comparative study of the ionized absorbers/emitters in 5 Seyfert galaxies observed with the Chandra HETGS and LETGS: NGC 5548, NGC 3783, NGC 3227, NGC 4051 and NGC 4151. The main objective of this study is to derive the physical and dynamical properties of this important ionized component of the gaseous AGN environment, in a uniform manner using the same modelling, for a sample of well studied nearby Seyferts. For some of these sources multiple observations are available, so we also study variations of the ionization of the gas in response to changes in the ionizing X-ray continuum, and apply our non-equilibrium photoionization models, to tightly constrain the electron density of the gas, and so its distance from the central ionizing source.
08/08/01
Mouchet Martine observatoire de Paris-Meudon
Place J. Janssen
92190 Meudon, France
Presentation 1 : Poster
Coherent radiative coupling in the two-phase models for black hole X-ray binaries and AGN
Julien Malzac(1), Martine Mouchet(2), Anne-Marie Dumont(2), Suzy Collin(2)
(1) Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, I. (2) Luth, Observatoire de Paris Section de Meudon, 92190 Meudon
The X-ray emission from galactic black holes and Seyfert galaxies is generally understood in term of two-phase models. Such models postulate that a hot plasma ($\sim$10$^{9}$ K) is cooled by inverse Compton scattering of soft X-ray photons arising from relatively colder material ($\sim$ 10$^{7}$ K), in the inner part of the accretion flow. We present the first simulated broad-band spectra produced in the context of such models and taking into account the radiative coupling between the two phases. This coupling is achieved using three radiative transfer codes: a non-linear Monte-Carlo code, a photo-ionisation code TITAN and a linear Monte-Carlo code NOAR. Our treatment accounts simultaneously for energy balance and Comptonisation in the hot phase, together with reprocessing, reflection, ionisation and energy balance in the cold phase. We show that such a detailed computation of the ionization and of the reprocessing has a great influence on the escaping spectra.
09/04/01
Mundell Carole Astrophysics Research Institute
Liverpool John Moores University, Twelve Quays House, Egerton Wharf
CH41 1LD Birkenhead, UK
Presentation 1 : Poster
The Host Galaxy-AGN connection - is neutral gas the key?
C.G. Mundell
Supermassive black holes are thought to be ubiquitous in bulge-dominated galaxies and the standard model of Active Galactic Nuclei (AGN) invokes the release of gravitational energy due to accretion of material onto a central black hole. What determines the presence and degree of nuclear activity, however, remains an unanswered question. Unlike quasar activity, which seems to coincide with the build-up of galactic-size structures, activity in nearby AGN with well-established host galaxies, must involve re-activation of their central black holes. Neutral hydrogen (HI) is a key tracer of galactic structure and dynamics and responds most readily to perturbations caused by tidal disturbance and non-axisymetric gravitational potentials - perturbations which have been mooted as possible triggers of nuclear activity. I present here an HI imaging study of a heterogeneous sample of nine nearby Seyfert galaxies and describe plans for a new HI survey which aims to investigate the role of the host gas in triggering and fuelling of nuclear activity on a statistical basis.
02/27/02
Nagar Neil Arcetri Observatory
Largo E. Fermi 5
50125 Florence, ITALY
Presentation 1 : Poster
Unveiling hidden AGNs in ULIRGs and low-luminosity AGNs through high-frequency radio observations.
Neil M. Nagar, Heino Falcke, Andrew S. Wilson
A compact (sub-parsec), high ($> 10^8$ K) brightness temperature radio core is a reliable indicator for the presence of an accreting massive black hole in a galaxy nucleus. Detecting such cores is facilitated by the absence of significant obscuration at high gigahertz frequencies (as compared to the UV to IR), and the availability of sensitive radio telescopes delivering the required resolution. Our high frequency high-resolution radio survey of all (~200) low-luminosity active galactic nuclei (AGNs) from the Palomar sample of ~500 nearby bright galaxies has found high brightness-temperature compact radio cores in almost half of all LINERs and low-luminosity Seyferts. The radio core properties (morphologies, luminosities and spectral shapes) provide strong evidence for the presence of accreting massive black holes in a large fraction, perhaps all, of LLAGNs, with the nuclear radio emission originating in either the accretion inflow onto the massive black hole or from jets launched by this black hole - accretion disk system. Current data favor the latter interpretation. We are now conducting a similar investigation on a complete sample of 118 ultraluminous infra-red galaxies (ULIRGs). High resolution radio data have now been obtained, and will be used to determine the incidence and evolution of AGN activity, and the interplay between AGN and star-formation activity in ULIRGs. A comparison between ULIRGs at different merging stages, and with our similar observations of (isolated) low-luminosity AGNs will be used to test the effect of mergers on AGN activity. Results of both studies above will be presented, and discussed in the context of black hole growth through merging and accretion.
11/30/01
Narayan Ramesh Harvard-Smithsonian Center for Astrophysics
60 Garden Street, MA
02138 Cambridge, USA
Presentation 1 : Invited
Accretion Modes in Galactic Nuclei: Theory versus Observations
Ramesh Narayan
There is good reason to believe that accretion in bright AGN proceeds via a radiatively efficient mode. The accretion flow is expected to be in the form of an optically thick and geometrically thin/slim disk. The big blue bump in bright quasars and the relativistically broadened iron K-alpha line in some Seyferts confirm this expectation. Detailed comparisons of the model with observations have, however, had only limited success. The substantial X-ray emission seen in bright AGN must arise in optically thin gas, which is presumed to be located in a corona above the optically thick disk. In contrast to bright AGN, low-luminosity galactic nuclei have no blue bump and show every indication of not having optically thick disks. In these systems, observations require the presence of a radiatively inefficient mode of accretion such as an ADAF, CDAF or related flow. The accretion is expected to proceed via an optically thin and geometrically thick/quasispherical flow. Models agree qualitatively with the observations, but many details remain unclear. Transition objects between the two classes are of great interest as they could reveal how the flow changes from an optically thick to an optically thin state as a function of decreasing luminosity. LINERs, BL Lacs and XBONGs have been variously identified as such transition objects.
11/18/01
Natarajan Priyamvada Dept. of Astronomy, Yale University
260 Whitney Avenue
06511 New Haven, U. S. A.
Presentation 1 : Poster
The dying gasps of binary black holes
Priyamvada Natarajan and Philip Armitage
We present the results of our work on the merger of binary black holes taking into account the effect of the inner accretion disk.
02/28/02
Nayakshin Sergei Max Planck Institut fur Astrophysik
Karl Schwarschild Str. 1
D-85741 Garching, Germany
Presentation 1 : Invited
Sergei Nayakshin.
As emphasized several years ago, X-rays create a hot ionized skin on the surface of accretion disks. This skin changes reflected and even intrinsic spectra of disks substantially. While the main effects are in principle easy to understand, they are many. These effects are also non-linearly connected with the corona producing the X-rays, and are complicated in a time-dependent setting. Here I will review these effects and point out possible connections with observations. The main conclusion is that in no system there is an unambiguous spectral evidence for a cut-off, e.g. a hole, in the ``standard'' accretion disk at small radii. If time permits, I will also mention our latest work which explains the spectrum of our Galactic Center as due to condensation of hot gas onto the surface of the cool ``standard'' disk rather than an ADAF-type model.
08/29/01
Nelson Charles Drake University
Dept. of Physics and Astronomy, Drake University
50311 Des Moines, Iowa, USA
Presentation 1 : Poster
To Be Decided
Charles Nelson
To Be Decided
02/28/02
Netzer Hagai Tel Aviv University
School of Physics and Astronomy, Tel Aviv University
69978 Tel Aviv, Israel
Presentation 1 : Invited
BLR, NLR, Warm Absorber
11/30/01
Nicastro Fabrizio Harvard-Smithsonian Center for Astrophysics
60 Garden Street, MS-83
02155 Cambridge, USA
Presentation 1 : Poster
"Chandra and FUSE discovery of the Local IGM Filament"
F. Nicastro, A. Zezas, M. Elvis, F. Fiore, A. Fruscione, S. Mathur
Chandra and FUSE spectra of the blazar PKS 2155-304 show resonant absorption from local highly ionized gas. The derived physical properties of this gas strongly suggest an extragalactic origin. Based on this evidence, and on the statistical analysis of FUSE and Chandra spectra of other 12 randomly distributed AGNs, we propose (Nicastro et al., in preparation) that the absorption lines from such highly ionized medium are tracking an IGM filament of warm gas. This filament is collapsing towards our galaxy, in the Virgo direction, consistent with what predicted by detailed hydrodynamical simulation for the formation of structure in our own supercluster environment.
02/26/02
Nishikawa Ken-Ichi Rutgers University
Department of Physics and Astronomy
NJ 08854 Piscataway, USA
Presentation 1 : Poster
3-D General Relativistic MHD Simulations of Generating Jets
K.-I. Nishikawa, S. Koide, K. Shibata, T. Kudoh, H. Sol, L.X. Li, J. P. Hughes, P. Hardee, R. Blandford
We have performed a first fully 3-D GRMHD simulation with Schwarzschild black hole with a free falling corona. The simulation results show that a jet is created as in previous axisymmetric simulations. However, the time to generate the jet is longer than in the 2-D simulations. We expect that due to the additional azimuthal dimension the dynamics of jet formation can be modified. We will report formation mechanisms of jet from an accreting black hole.
Presentation 2 : Poster
3-D RMHD simulations of internal shocks in relativistic jets
K.-I. Nishikawa, P. Hardee, R. Blandford, S. Koide, H. Sol
We present 3-D numerical simulations of relativistic jets propagating with different injection conditions. One of the most important features of jets is helical magnetic field. at the same time velocity and/or velocity perturbations affect the internal dynamics of propagating jets. We will report new results with 3-D RMHD simulations and compare with observations.
01/10/02
Oknyanskij Victor SAI
13 Universitetsky Prospekt
119899 Moscow, Russia
Presentation 1 : Poster
Time Delays in NGC~4151
V.L. Oknyanskij, Keith Horne, V. M. Lyuty, S.Honda, K.Sadakane, S.Tanabe
Photometric UBVRI monitoring of NGC~4151 are used to measure wavelength-dependent time delays and variability amplitudes. The time delay increases with wavelength. In a blackbody reprocessing model, this implies temperatures decreasing with radius.
09/05/01
Omont Alain IAP Institute of Astrophysics
98b Bd Arago
75014 Paris, France
Presentation 1 : Oral
AGN and Starbursts at High Redshift
Alain Omont
Together with surveys for dust emission of field high z ultraluminous IR galaxies, the sensitivity of MAMBO/IRAM-30m and SCUBA/JCMT allows to probe mm/submm emission of large samples of high z candidates. Such studies are particularly successfull with known powerful high z AGN, QSOs and radiogalaxies, whose more than 80 have already been detected at 0.85-1.2mm. I will particularly report on the 60 bright QSOs recently detected by MAMBO/IRAM-30m. Within this limited statistics, confirmed by similar data from SCUBA/JCMT, there is no indication of a strong dependence of the QSO millimeter luminosity function on redshift in the range z=2-4.5, and only a mild dependence, if any, on the QSO (UV) bolometric luminosity. The dust origin of this redshifted FIR emission is well confirmed. The restframe FIR luminosity could approach 10^13 Lo. However, the origin of dust heating - starburst, AGN or both - remains unclear, although there are arguments, including CO detection in a few sources, for at least a partial starbust contribution, implying star formation rates maybe up to ~1000 Mo/yr. I will briefly address the situation of CO detections in about 15 prominent high z AGN, and the inferred information about molecular gas.
08/29/01
Pastoriza Miriani Instituto de Fisica, UFRGS
Av Bento Goncalves 9500; Campus do Vale
91501970 Porto Alegre RS, Brasil
Presentation 1 : Poster
Near-IR observations of Narrow-Line Seyfert 1 Galaxies
Miriani Pastoriza, Alberto Rodriguez-Ardila, Sueli Viegas & L.Prato
WE obtained 0.8-2.4 $\mu\,m$\ spectra at a resolution of R=700 of a sample of Seyfert 1 galaxies in order to study the near-infrared properties of these objects. We concentrate on the search of circumnuclear star-formation events
10/26/01
Peletier Reynier School of Physics and Astronomy, University of Nottingham
University Park
NG7 2RD Nottingham, United Kingdom
Presentation 1 : Poster
The 2-D structure and stellar populations of bulges from SAURON-measurements
R.F. Peletier and the SAURON team
to follow
08/28/01
Perrin Guy Observatoire de Paris
DESPA, 5, place Jules Janssen
92190 Meudon, France
01/14/02
Peterson Bradley Department of Astronomy, Ohio State University
140 West 18th Avenue
43210-1173 Columbus, OH, USA
Presentation 1 : Oral
Masses of Supermassive Black Holes in AGNs
B.M. Peterson
Reverberation techniques have been used to estimate the masses supermassive black holes in over 30 galaxies. There is now reasonably compelling evidence that the inferred masses are reliable to a factor of a few or so: (a) for AGNs for which both emission-line lags and line widths are well-determined, there is a virial-like relationship between these quantities, and (b) AGNs should the same relationship between black-hole mass and host-galaxy bulge velocity dispersion that is found in quiescent galaxies. We report on progress made in refining the measurements that contribute to these relationships and outline difficulties imposed by unknown systematics and how these systematics can be identified and quantified.
02/27/02
Petrucci Pierre-Olivier LAOG
414 rue de la Piscine
38041 Grenoble, France
Presentation 1 : Poster
New insights into the spectral variability of Seyfert galaxies
Petrucci P.O., Malzac J., Maraschi L., Papadakis I.
We will discuss recent results on the spectral variability of Seyfert galaxies as derived from analysis of BeppoSAX, XTE and XMM data. We show that the observed variability in Seyfert galaxies is generally consistent with fluctuations of the X-ray spectral slope with a nearly constant comptonised luminosity, i.e. the spectrum is mainly pivoting. In this context, we also discuss the growing evidence in favor of a significant fraction of the reflection features being formed at large distance from the central engine. We then present the influences it has on the spectral variability and more precisely on the reported $R$-$\Gamma$ correlation. We finally underline the importance of the model used to fit the primary continuum, especialy in anisotropic geometry, which may produce different trends and correlation between the physical parameters. We discuss these differences and their consequences for the physical models of the variability.
10/02/01
Pietrini Paola Dipart. di Astronomia e Scienza dello Spazio, Univ. di Firenze
Largo E. Fermi 2
50125 Firenze, Italy
Presentation 1 : Poster
Nuclear AGN outflow interacting with expanding stellar atmospheres: relevance to BLR modeling
Paola Pietrini and Guidetta Torricelli-Ciamponi
The presence of a dense star cluster around the central black hole in AGNs can affect both the dynamics and the emission of the global system. We analyze the interaction of expanding stellar atmospheres with a nuclear wind outflowing from the central region of a Seyfert-like AGN nucleus. The envelopes can be confined by the bow shock arising from the interaction with the AGN nuclear wind. A non-negligible amount of matter is fed into this nuclear wind as a result of stellar mass loss and possible star collisions; at the same time, the envelopes surrounding the stars, produced by the stellar mass loss, turn out to be suitable for reproducing the observed Broad Line Region emission.
10/05/01
Pogge Richard Ohio State University, Dept. of Astronomy
140 W. 18th Avenue
43210-1173 Columbus, OH, USA
Presentation 1 : Poster
STIS Spectra of the Nuclei of Seyfert 2 Galaxies
Richard Pogge (OSU), Paul Martini (OCIW), Joseph Shields (OU), Dale Fields (OSU)
I will present the results of a STIS spectroscopic study of the nuclei of 20 nearby Seyfert 2 galaxies. All are Seyfert 2s which have clearly detectable nuclei in WFPC2 images not obviously blocked by interstellar dust. The small (0.2-arcsec) slit of STIS provids a factor of 20-50 increase in contrast between the active nucleus and the surrounding starlight. We are searching for weak broad H-alpha lines in direct light and evidence of a blue continuum from either hot stars or perhaps the elusive "featureless continuum". Implications for understanding if we need a Seyfert 2 class will be discussed. Note to the SOC: This is a cycle 10 project currently in progress. We should have most of our spectra in hand an analyzed by the meeting, and are just now getting excellent and exciting spectra.
12/14/01
Porquet Delphine Service d'Astrophysique, CEA-Saclay
Ormes des Merisiers (bat. 709)
91191 Gif-sur-Yvette, France
08/28/01
Poutanen Juri University of Oulu
Division of Astronomy, P.O.Box 3000, University of Oulu
90014 Oulu, Finland
01/17/02
Pronik Iraida Crimean Astrophysical Observatory
Settl Nauchny
98409 Crimea, Ukraine
Presentation 1 : Poster
Do Identical Mechanisms Produce Intranight and Year Optical Variable Radiation of AGNs?
I.Pronik, Crimean Astrophysical Observatory, Nauchny, 98409, Crimea, Ukraine
The data on intranight and years variations of optical continuum and night-to-night Balmer line variations in Seyfert galaxies collected from Crimean papers were considered. It was shown that characteristics of intranight and years variations and their evolution with time are different. It was supposed that a conceivable sources of intranight continuum variations as well as night-to night Balmer line variation can be short-lived shocks in long-lived flows.
03/01/02
Punch Michael PCC-Collège de France
11, Place Marcelin Berthelot
75231 Paris Cx05, France
03/01/02
Ramirez Antonio Instituto de Astronomia, UNAM
Circuito de la Investigacion, Ciudad Universitaria, Mexico
04510 Mexico D.F., Mexico
Presentation 1 : Poster
Spectral Characterization of Microvariability in Quasars
A. Ramirez, J.A. de Diego, D. Dultzin-Hacyan, E. Benitez
Microvariations (magnitude changes of several hundredths in timescales ranging from minutes to hours) may arise from three sources: jet and accretion instabilities and gravitational microlensing events. Each may produce different changes on the quasars continuous spectra. For this reason, BVR observations can yield a high degree of discrimination between these microvariability sources. The monitoring of selected radio-quiet and radio-loud quasars samples is presented. Ours results to cast light on the physical models for microvariations.
12/28/01
Ramos de Oliveira Marcio Observatoire de Paris
61, Av. de l'Observatoire
75014 Paris, France
Presentation 1 : Poster
TBD

02/21/02
Reeves James University of Leicester
Department of Physics and Astronomy, University of Leicester, University Road
LE1 7RH Leicester, UK
Presentation 1 : Oral
XMM-Newton Observations of AGN; the iron K line and the central engine
James Reeves
XMM-Newton observations of type I AGN with are presented. The properties of the iron K emission lines are reviewed, the majority of objects show narrow iron lines from cold matter that must originate far from the inner accretion disc, perhaps in the putative molecular torus. The strength of this narrow line decreases with luminosity, implying a reduction in the solid angle of the obscuring material - this may have implications for the occurance of type II quasars. To date, there are only a few examples of the broad iron K line with XMM-Newton, but in one case (MCG -6-30-15) the extreme breadth requires a Kerr metric for the central black hole. I will also discuss new X-ray spectral features, including two AGN where deep iron K-shell absorption is observed, suggesting that a high column of ionised matter exists along the line of sight, but close to the central engine.
Presentation 2 : Poster
XMM-Newton Observations of the luminous quasar PDS 456
James Reeves, Paul O'Brien, Ken Pounds.
We present recent XMM-Newton and Beppo-SAX observations of the most luminous nearby quasar, PDS 456. Rapid variability, on doubling timescales corresponding to <3 Schwarzschild radii light crossing size, will be discussed. The complex X-ray spectrum, showing evidence of absorption via highly ionised species of iron, will also be presented.
03/01/02
Rhee Joseph University of California at Los Angeles
Division of Astronomy & Astrophysics, 8371 Mathematical Sciences Building
90095-1562 Los Angeles, United States of America
Presentation 1 : Poster
Testing the Standard AGN Model Using Near-infrared Spectroscopy of Seyfert Galaxies
Joseph H. Rhee & James Larkin
We report new near-infrared spectroscopy of Seyfert galaxies using the Gemini twin channel near-infrared camera on the Shane 3m telescope at Lick Observatory. We directly test the standard AGN model by measuring extinctions to both broad and narrow line regions for different Seyfert classes using the Pa Beta and Br gamma emission lines. With the unique design of the Gemini camera, full J and K spectra were taken simultaneously through the same slit greatly reducing systematic errors in the line ratio measurement that can be introduced by seeing variation and slit positioning. We find that for our sample of Seyfert 1s, the line ratios of PaB/Brg are not only comparable in both broad and narrow line regions but also are consistent with case B recombination indicating little or no extinction. Seyfert 2 galaxies, however, show substantial reddening to the narrow line regions. Historically, studies have found dust extinction in the narrow line regions of both Seyfert 1s and Seyfert 2s. We compare our results with recent optical data from the literature and find significant support for our findings. Several possible scenarios are discussed to explain this apparent difference of narrow line ratios between Seyfert 1s and Seyfert 2s, which represent modifications to the unified model. We also analyzed CO band-head absorption features to look for evidence of recent star formation activity. The CO band-head, especially in Seyfert 1s, show heavy contamination from nonstellar radiation, which is correlated with an H-K nuclear color index. After correcting for this effect, we confirm that the evidence of recent star formation in Seyfert 2's, as indicated by the CO spectral index, is weak. Finally we will discuss our plans to utilize the Keck Telescope to observe spatially resolved IR spectra of Seyfert 2's to attempt to localize the obscuring material.
03/02/02
Ridgway Susan The Johns Hopkins University
Dept. of Physics and Astronomy, 3700 N. Charles St.
21218 Baltimore, U.S.A.
Presentation 1 : Poster
The nature of radio-optical alignments in faint radio sources
S.E. Ridgway (JHU), M. Lacy (SSC, Caltech)
Study of the host galaxies and environments of high redshift AGN is proving a valuable complementary probe of current theories of how galaxies form and evolve. By observing the hosts of such objects, we can study high-z galaxies without pre-selecting for unusual star-forming properties. It is important, however, to understand how the strength of the AGN may affect the properties of the hosts. One measure of the effect the radio source may have on the host galaxy is the alignment seen between the rest-frame ultraviolet morphology of the host and the radio structure in high-redshift radio galaxies, the so-called ``alignment effect''. We discuss here the results of an HST optical and ground-based near-infrared imaging study of a sample of z ~ 1 low-radio-luminosity galaxies and quasars. We compare the properties of these radio source hosts, including magnitude, scale size and degree of ``alignment effect'', to those of the highly radio luminous 3C sources at similar redshifts.
Presentation 2 : Poster
The Optical-UV colors of the Hosts of High Redshift Radio-quiet Quasars
S.E. Ridgway (JHU), T.M. Heckman(JHU), D. Calzetti(STScI), M. Lehnert(MPE)
Understanding the links between the formation and evolution of the AGN population and the formation and evolution of galaxies requires investigation of the relationship between these populations at high redshift, where the quasar luminosity function is reaching a maximum. We have made a deep space-based near-infrared imaging study of the properties of the host galaxies of z ~ 2 -- 3 radio-quiet quasar hosts and compared them to those of the other known high-z galaxies, the Lyman break galaxies and the hosts of radio-loud objects. We found that the RQQ hosts have rest-frame optical magnitudes and sizes that are similar to the Lyman break galaxies, and are much fainter than most radio-loud hosts at these epochs. We have also obtained rest-frame ultraviolet imaging of this sample, and will use this to study the UV--optical colors of the hosts. These will allow us to compare the star-forming properties of the quasar hosts with those of the Lyman break galaxies.
01/22/02
Rigopoulou Dimitra Max-Planck-Institut fuer extr. Physik
Postfach 1312
85741 Garching, Germany
Presentation 1 : Poster
An ISO-SWS survey of molecular hydrogen in Starburst and Seyfert Galaxies
D. Rigopoulou, R. Genzel, D. Lutz, A. Moorwood
We present results from a survey of molecular hydrogen emission from a sample of Starburst and Seyfert galaxies carried out with the Infrared Space Observatory (ISO). Pure rotational H_2 emission has been detected in a number of extragalactic objects and a variety of environments. A number of transitions from S(7) to S(0) are detected in both Starbursts and Seyferts. Using excitation diagrams we derive temperatures and masses of the ``warm'' molecular hydrogen. We find that the temperature of the ``warm'' gas is similar in Starbursts and Seyferts (those Seyferts for which we have firm detections of the S(0) line) with a value of around T$\sim$150 K. This ``warm'' gas accounts for as much as 10\% of the total galactic mass (as probed by CO molecular observations) in Starbursts. whereas it ranges between 5--30% in Seyferts. We suggest that X-rays from the central AGN could be responsible for heating up a larger fraction of the gas in Seyferts. We also find that although PAH and H$_{2}$ line emission correlate well in Starbursts and the large scale emission in AGN, H$_{2}$ emission is much stronger compared to PAH emission in cases where a ``pure'' AGN dominates the energy output.
09/03/01
Risaliti Guido Osservatorio Astrofisico di Arcetri
Largo E. Fermi 5
50125 Firenze, Italy
Presentation 1 : Poster
Chandra observation of X-ray weak quasars
G Risaliti
I present preliminary results of a small survey of X-ray weak quasars performed with Chandra. These objects, which were selected cross-correlating an optical spectroscopic survey with the ROSAT WGACAT, are more than 10 times weaker in the soft X-rays than "normal" PG quasars. Chandra is able to distinguish whether these sources are intrinsically weak in the X-rays or obscured by gas along the line of sight.
Presentation 2 : Poster
Hard X-ray study of ULIRGs
G. Risaliti et al.
We present BeppoSAX observations of a few new Ultraluminous Infrared Galaxies. The sources are from an unbiased sample selected through the total infrared luminosity. This selection avoids a bias towards starburst-dominated objects, which affects most of the ULIRG samples, selected using the 60 micron flux density. Therefore, this sample is best suited to investigate the relative contribution of AGNs and starbursts to ULIRGs. The high energy instrument PDS (20-200 keV) is able to discover very highly obscured AGNs. Therefore, this work can also put a significant lower limit to the presence of QSO2s inside ULIRGs.
12/04/01
Robson Ian joint astronomy centre
660 n.aohoku place
96720 hilo, usA
Presentation 1 : Poster
Submillimetre observations of a sample of very high redshift quasars
Ian Robson, Robert Priddey, Kate Isaak, Richard McMahon, Chris Pearson, Matt Fox & Rob Ivison.
As part of an extensive programme to determine the submillimetre emission from quasars over a wide range of redshift, we have used SCUBA on the JCMT to investigate some of the highest redshift quasars yet identified. We have now observed almost all the currently known z>5 quasars at ~1.5mJy RMS or better, which comprise 12 objects in total. Four of these objects have been detected: two of them (SDSS0756+4104, z=5.1 and SDSS0338+0021, z=5.0) are relatively bright objects with an S(850microns>10mJy; the other two are amongst the highest redshift objects known (SDSS1044+0125, z=5.7; SDSS1306+0536, z=6.0). The submillimetre emission is due to cold dust in the parent galaxy and most is currently assumed to be due to star formation rather than AGN heating. In either case, at z=6, the age of the Universe is only about 1Gyr in current favourite Lambda cosmology, which is starting to become a tight constraint on the formation of a SMBH and the generation of dust. Current follow-up observations involve SCUBA imaging of the environments of these quasars because if we are detecting the rare peaks in overdensity, we might expect to find evidence of biased galaxy formation in the vicinity, as has been hinted at from other SCUBA imaging.

10/26/01
Rodriguez-Ardila Alberto Instituto Astronomico e Geofisico - Universidade de Sao Paulo < /td>
Avenida Miguel Stefano 4200
04301-904 Sao Paulo, Brazil
Presentation 1 : Poster
Low-ionization lines in the Broad Line Region of AGNs
Rodriguez-Ardila A., Viegas, S., Pastoriza, M., Prato, L.
Near-infrared spectroscopy is used to study the physical conditions and excitation mechanisms of the low-ionization species such as FeII and OI, emitted by the BLR. Primary cascade lines of FeII arising from the decay of upper levels pumped by Ly-alpha fluorescence are resolved and identified, for the first time, in AGNs. We show that the FeII lines located at 0.999, 1.050, 1.086 and 1.112 microns are the strongest FeII lines in the 0.8-2.4 micron interval. A combination of Ly-alpha fluorescence and collisional excitation are found to be the main contributors. For OI, we found that contrary to the general believed, Ly-beta fluorescence is not the dominant mechanism responsible for the formation of its permitted lines.
Presentation 2 : Poster
Reddening indicators for the broad line region of AGNs
Rodriguez-Ardila, A., Viegas, S., Pastoriza, M.
Multiwavelength spectroscopy is used to study the reddening that af fects the BLR by means of the OI and other permited lines. The values of E(B-V) derived from the OI 1304/8446 agree with those obtained using the Balmer decrement and the HeII lines. They all points to low to moderare amounts of reddening within the BLR. Intrinsic line ratios between the most useful indicators are revisited and give light about the most important destruction mechanisms that may affect them.
09/12/01
Rodriguez-Fernandez Nemesio J. OAN
Apdo. 1143
E28800 Alcala de Henares, Spain
02/01/02
Rokaki Evlabia Sect of Astrophysics, Astronomy & Mechanics, Univ. of Athens
Zografos,
15784 Athens, Greece
Presentation 1 : Poster
"Evidence of a Disc-like Geometry in the Superluminal Quasars"
E. Rokaki \& A. Lawrence
In a sample of 18 superluminal quasars with lower limits of the jet outflow angle (\th) between 0 and 30 degrees, and with \Ha line emission we find: 1) a positive correlation between line velocity width at half maximum (FWHM) and \th, implying a ratio of planar to random broad line region (BLR) motions to be $\sim$ 10:1, and 2) a positive correlation between the line equivalent width (EW) and \th. The slope of this trend is stronger than the expected by a geometrical thin disc, while the strong flat trend of EW with the Doppler factor, rules out an important optical relativistic beaming in the 15 strong lined objects. The beaming found in these objects might be due to a geometrical thick disc, or/and, to an increasing of the optical absorption with \th.
Presentation 2 : Poster
SMA: Synthetic Microscopic Astronomy
E. Rokaki
The superluminal quasars are well constrained in orientation and therefore a key sample for testing our understandings of basic physics in AGN. Various components of emission (radio, optical as high energy radiation) coming from different size regions of the nucleous can be "seen" in synthetic images as a function of the viewing angle.
09/17/01
Rozanska Agata N.Copernicus Astronomical Center
Bartycka 18
00-716 Warsaw, Poland
02/17/02
Russell David STScI
3700 San Martin Drive
MD 21218 Baltimore, USA
Presentation 1 : Poster
HST and VLA Observations of the jet of 3C273
D.A. Russell (1,2), C.P. O'dea(1), S.A. Baum(1), J.P. Leahy(2)
(1) STScI; (2) Jodrell Bank Observatory, University of Manchester
We present new HST/STIS images of the jet in 3C273 along with a new radio map produced from previously published VLA data. This is the first in a series of studies of a sample of extra-galactic jets. We find 3C273's jet is significantly wider in the radio, although the first knot has the same width at both frequencies. We also find the bright optical knots to be narrower than the general jet emission. The radio emission is observed to extend beyond the visible optical emission to a peak with no visible optical counterpart. Spectral index calculations using these and previous HST (Jester {\it et al.} 2001) observations clearly show the optical spectral index steepens smoothly along the jet from -0.9 at the first knot to around -1.6 at the end of the optical jet. Although no relation between the local brightness and the spectral index of the jet is observed. Chandra data (Marshall {\it et al.} 2001) has shown there must be a break in the spectrum in the near-UV and evidence of the near-UV break is found for a number of knots using the STIS near-UV MAMA detector. These results suggest that (1) in 3C273 the knots are not sites of significant particle re-acceleration, (2) we are seeing the effects of radiative losses on the relativistic electrons, (3) the higher energy particles are concentrated near the center of the jet, possibly in a region of lower magnetic field.
Financial support for this work was provided by NASA/STScI.
10/19/01
Saikia Dhruba J. National Centre for Radio Astrophysics, TIFR
Pune University Campus, Ganeshkhind, Post Bag 3,
411 007 Pune, India
Presentation 1 : Poster
Compact radio sources as probes of the central regions of AGN
D.J. Saikia et al.
We present high-resolution, total-intensity and linear polarization observations of cores, nuclear jets and compact radio sources at different radio frequencies. We discuss the constraints these place on our understanding of the physical conditions of the central regions of active galaxies and the canonical picture of an AGN.
Presentation 2 : Poster
Circumnuclear star formation and nuclear activity
D.J. Saikia et al.
The dynamics and relationships between gas inflow processes, circumnuclear star formation and the presence of an active nucleus are important since they might provide valuable leads towards understanding the transport of gaseous material towards the nuclear regions of active galaxies. We summarise our results on a few galaxies, and discuss the possible relationships between circumnuclear star formation and nuclear activity.
03/18/02
Sauty Christophe observatoire de Paris-Meudon
5 Place J. Janssen
92195 Meudon, France
Presentation 1 : Poster
Relativistic Spherical Outflows from a Black Hole magnetosphere
Meliani Zakaria, Sauty Christophe (L.U.Th.)
We have explored a new relativistic extension of the classical polytropic equation of state to study Parker-type winds, with a polytropic index going from isothermal to adiabatic. Our assumption allows us to have a plasma with both a high ultra relativistic temperature profile at the base of the corona and a classical lower temperature in the outer region. The model also includes the relativistic effects of the Black Hole metric.
As a result, relativistic effects both in the temperature and in the metrics seems to favor the acceleration of the wind. The classical constraint on the polytropic index that should be less than 3/2 is less severe in the frame of relativistic winds. As a consequence, coronae with relativistic temeratures in the central part of AGNs are likely to be able to accelerate the plasma to high relativistic speeds. This may be an alternative or a strong supply to the usual magnetocentrifugal acceleration invoked for the formation of relativistic jets.
Presentation 2 : Poster
On a MHD classifical of AGN jets
Sauty Christophe (L.U.Th., observatoire de Paris), Tsinganos Kanaris (University of Athens), Trussoni Edoardo (Osservatorio Astronomico di Torino)
Winds and jets associated with compact astrophysical objects such as AGN and micro-Quasars are thought to be plasmas escaping from a rotating and magnetized accretion disk with a magnetosphere around a central black hole.
It is proposed that in a space where the two main variables are the energy of the magnetic rotator of the central objects and the angle between the line of sight and the ejection axis, some observed characteristics of AGN jets can be understood. A criterion for the transition of the morphologies of the outflows from highly collimated jets to uncollimated winds is given. It is based on the analysis of a particular class of exact solutions and may somehow generalize other earlier suggestions, such as the spinning of the black hole, the fueling of the central object, or the effects of the environment.
Thus, while the horizontal AGN classification from Type 0 to Types 1 and 2 may well be an orientation effect -- as in the standard model -- the vertical AGN classification with uncollimated outflows (radio-quiet sources) and collimated outflows (radio-loud sources) depends both, on the efficiency of the magnetic rotator and the environment in which the outflows propagate.
09/02/01
Scarpa Riccardo European Southern Observatory
Alonso de Cordova 3107, Vitacura
Casilla 19001 Santiago, Chile
Presentation 1 : Poster
Optical jets in AGN
R. Scarpa, C. M. Urry, R. Sambruna, T. Cheung
We report the results of an HST survey of 17 AGN, selected solely for having a well developed radio jet bright enough to be detectable with HST for a normal radio-to-optical spectral index. It is found that optical jets are much more common then expected, been detected in ~30% of the cases. The data are then combined with Chandra X-ray and VLA radio observations, to provide a unique dataset for investigating AGN jets physics.
08/31/01
Schilizzi Richard Joint Institute for VLBI in Europe
Postbus 2
7990AA Dwingeloo, The Netherlands
02/21/02
Schinnerer Eva California Institute of Technology
Radio Astronomy, MS 105-24
CA 91125 Pasadena, U.S.A
Presentation 1 : Poster
Gas Dynamics in the Central Kilo-Parsec of two Barred Galaxies
Schinnerer, Maciejewski, Moustakas, Scoville
We report on the molecular gas properties in the central kilo-parsec of the almost face-on double barred Seyfert 2 galaxy NGC 4303 (M 61), using the CO(1-0) line emission observed with the Owens Valley Radio Observatory (OVRO) millimeter interferometer. The bulk of the molecular line emission comes from two straight gas lanes which run north-south along the leading side of the large-scale primary bar. Velocity deviations of up to 90 km/s from the mean rotational velocity are associated with these gas lanes. Inside a radius of about 5''(400 pc) the molecular gas forms a spiral pattern which, for the northern arm, can be traced to the nucleus. The southern gas spiral arm is very likely disturbed by the impact of the massive star formation seen in the UV continuum. The high angular resolution of our OVRO data (2'' = 150 pc), accompanied by the archival HST images, allows for a comparison against dynamical models of gas flow in the inner kilo-parsec of single- and double-barred galaxies. We find that the overall properties of the molecular gas are in agreement with models for the gas flow in strong bars, and the spiral structure in the inner kilo-parsec can be due to a gas wave initiated by the potential of the primary bar. As the inner bar is much smaller than the distance between the two gas lanes, its presence may not inhibit the nuclear spiral seen in CO, but the starburst ring seen in UV is consistent with models of double bars.
09/17/01
Schmitt Henrique National Radio Astronomy Observatory
1003 Lopezville
NM87801 Socorro, USA
Presentation 1 : Poster
The orientation of accretion disks relative to their host galaxies in AGN
Henrique R. Schmitt
I will present the results of recent developments on the study of the orientation of jets relative to nuclear dust disks in radio galaxies and galaxy disks in Seyfert galaxies. I show that the jets are randomly oriented relative to the disks, which seems to be contradictory, since the simplest expectation suggest that the black hole and galaxy disk axes, the source of gas to fuel it, should be aligned and consequently the jets should be perpendicular to the disks. I will discuss the implications of these results for the structure of accretion disks and host galaxy disks, as well as on the processes responsible for feeding the nucleus.
Presentation 2 : Poster
The Frequency of Active and Quiescent Galaxies with Companions
Henrique R. Schmitt
We analyze the idea that nuclear activity, either AGN or star formation, can be triggered by interactions, studying the percentage of active, HII and quiescent galaxies with companions in the Palomar survey. A first analysis of the results showed that there is a larger percentage of LINERs, transition, and absorption line galaxies with companions than Seyferts and HII galaxies. However, we find that when we consider only galaxies of similar morphological types (ellipticals or spirals), there is no difference in the percentage of galaxies with companions among different activity types, indicating that the former result was due to the morphology-density effect. We also find that the percentage of HII galaxies with companions increases as their H$\alpha$ luminosity increases, in agreement with previous results. We compare these results with previous ones and discuss their implications.
08/28/01
Schreier Ethan Space Telescope Science Institute
3700 San Martin drive
21218 Baltimore, MD, USA
Presentation 1 : Poster
Morphology of AGN Host Galaxies observed with HST
Ethan J Schreier
03/01/02
Schurch Nicholas University of Leicester
Dept. of Physics and Astronomy, University Road
LE1 7RH Leicester, Uk
Presentation 1 : Poster
Probing the ionization structure of the extended NLR in NGC 4151
Schurch N.J, Warwick R.S, Kinkhabwala A, Griffiths R.E, Kahn, S.M
Recent Chandra observations of the archetypal Seyfert 1.5 galaxy, NGC 4151, have revealed extended soft X-ray emission on a similar scale and at a similar position angle to the OIII ionization cones identified in HST images. Here we discuss the results of recent XMM-Newton observations of NGC 4151 for which the combined exposure time is ~125ks. The XMM RGS data confirm the Chandra finding that the soft x-ray spectrum of NGC 4151 is extremely rich in emission lines and radiative recombination continua with little evidence for any underlying continuum emission. We find that the soft X-ray spectrum of NGC 4151 is remarkably similar to that of NGC 1068 and can be modelled in terms of photoionized and photoexcited gas present in the extended NLR of the source.
Presentation 2 : Poster
Joint spectro-imaging of NGC 4945 with XMM-Newton and Chandra
Schurch N.J, Roberts T.P, Warwick R.S
A recent 20ks XMM-Newton observation of NGC 4945 has revealed many X-ray emission components in this nearby galaxy. Chief amongst these components are the heavily absorbed Seyfert 2 nucleus, a marginally extended starburst region and an associated soft X-ray outflow region, which we i nterpret the outflow as a mass-loaded superwind. In addition we observe a luminous X-ray source population, including several ultra-luminous X-ray sources,and extensive unresolved soft X-ray emission in the plane of the galaxy. We present an imaging analysis of all the components and a spectral analysis of the AGN, the starburst, the outflow and the diffuse emission.
08/30/01
Schwartz Dan Smithsonian Astrophysical Observatory
60 Garden St.
02138 Cambridge, MA, USA
Presentation 1 : Poster
Chandra Observations of the Redshift 6 SDSS Quasars
Dan Schwartz
Chandra snapshot observations of the three most distant quasars then known, at redshifts 5.82, 5.99, and 6.28, gave signficant detections even in the short, 6 -- 8 Ks, observations. Their X-ray to optical luminosity ratios indicate that quasars will easily be detectable in X-rays if they exist at even larger redshifts.
The present observations hint at two exciting discoveries. An extended X-ray source 23 arcsec from SDSS1306+0356 is most likely a jet, emitting inverse Compton radiation from the Cosmic Microwave Background. SDSS 1030+0524 does not appear to be a point source, and may be a gravitationally lensed system.
Presentation 2 : Poster
Results from a Complete Chandra Survey of Radio Jets
D. A. Schwartz, H. L. Marshall, D. Worrall, M. Birkinshaw, J. Lovell, E. Perlman, D. Murphy, D. Jauncey, B. Miller, R. Preston
We report preliminary results from the first targets observed as part of a program to image the X-ray jets in a complete sample of radio selected jets. We have acquired Australian Telescope Compact Array and Very Large Array data with resolution 1", matching the Chandra resolution. PKS 1202-262 and PKS 0208-512 show dramatic coincidence with the initial radio jet, with the X-ray emission dropping off at the large angle radio bends, like the case of PKS 0637-752. We have 10 further observations scheduled before summer 2002.
02/28/02
Scoville Nick Caltech
astronomy 105-24 , Caltech
91125 Pasadena, Ca, USA
Presentation 1 : Invited
Starburst and AGN Models
Nick Scoville
I will review possible scenarios and models linking nuclear starburst and AGN activity with emphasis on observatioanl constraints.
02/28/02
Shapovalova Alla Special Astrophysical Observatory, Russian Academy of Sciences
house1/36, Nizhnij Arkhyz, Karachai-Cherkess Republic, Russia
369167 Nizhnij Arkhyz, Russia
Presentation 1 : Poster
Spectroscopy and Photometric Monitoring of Seyfert Galaxies in 1996-2001.
Shapovalova A.I., Burenkov A.N., Carrasco L., Chavushyan V.H., Doroshenko V.T., Dumont A.M., Valdes J.R., Bochkarev N.G., Collin S., Lyuty V.M., Spiridonova O.I., Vlasuyk V.V., Borisov N., Kurtanidze O., Mikhailov V.P.
The results of spectral and photometric monitoring of some Seyfert galaxies in 1996-2001 are presented. The CCD spectral monitoring was carried out at the 6-m and 1-m telescopes of SAO RAS (Russia) and 2.1m GHO telescope at Cananea (Mexico). BVRI CCD photometric monitoring was fulfiled at 1m , 70 cm or 60 cm telescopes of 4 FSU observatories. The variations of the H-beta broad emission line profiles and continuum fluxes are investigated. Objects are showed some time-changing features: "double peaks" in very broad wings of H-beta emission line. The flux in H-beta wings and line core varied quasi-simultaneously, with the same lag relative to the continuum variations. This behavior is indicative of predominently circular motions in BLR and excludes models of broad line formation in biconical gas streams or jets. Our results favour the formation of the broad emission lines in an accretion disk.
Presentation 2 : Poster
H-beta Blue and Red Bumps Velocity Variations of 3C390.3 in 1995-1999.
Shapovalova A.I., Bochkarev N.G., Burenkov A.N., Carrasco L., Chavushyan V.H., Collin S., Doroshenko V.T., Dumont A.M., Valdes J.R., Vlasuyk V.V.
From the spectral monitoring of 3C390.3 in 1995-1999 we have obtained that the H-beta blue bump radial velocity variations follow the same trend found by Eracleous et al.(1997). Their model for a binary BH with a very large mass (>10^11 solar mass) seems to fit our data as well. Hence, our results provide further support to the rejection of the massive binary BH hypothesis for 3C 390.3. From the H-beta difference profiles we found that the radial velocity variations of the blue and red bumps and their differences are unticorrelated with the light curves of H-beta and continuum radiation. This implies that the zone that contributes most of the energy to the emitted line changes in radius within the disk. These transient phenomena are expected to result from the variable rate of accretion close to the central source.
11/02/01
Shastri Prajval Indian Institute of Astrophysics
Sarjapur Road
560034 Bangalore, INDIA
Presentation 1 : Oral
Jets in Seyfert Galaxies
Shastri, P., Lal, D.V. & Gabuzda, D.C.
We will present the main results from a study of the pc-scale radio structure of our matched sample of Seyfert galaxies, specifically selected to test the Unified Scheme. We chose purportedly face-on (Seyfert~1) and edge-on (Seyfert~2) objects that are intrinsically similar and minimized selection biases. Our results are mostly consistent with the predictions of the scheme. We are also able to look for correlations with Seyfert properties at other wavelengths and comment on the nature of the radio jets.
01/30/02
Shemmer Ohad Tel-Aviv University
Haim Levanon st.
69978 Tel-Aviv, Israel
Presentation 1 : Poster
Is There a Metallicity-Luminosity Relationship in AGN? The Case of NLS1s.
Ohad shemmer & Hagai Netzer
Our new metallicity measurements (based on the Hamann & Ferland 1993 method) for a sample of AGN, including several NLS1s, indicate that while most broad-line AGN show a clear metallicity-luminosity correlation, NLS1s, that were not included in the original Hamann & Ferland analysis, deviate significantly from this relationship at low luminosities. If BLR metallicities, in all AGN, are accurately derived by the Hamann & Ferland method, then the high values we detect in NLS1s match those of some high-redshift high-luminosity quasars. This suggests that the metallicity-luminosity relationship is not a simple two-parameter dependence and that the hidden parameter may be related to a fundamental AGN physical property, such as the accretion rate, or the age of the central black hole.
02/27/02
Shields Joseph Ohio University
Physics and Astronomy Department
45701 Athens, Ohio, USA
Presentation 1 : Poster
Energy Sources in the Lowest Luminosity Active Galaxies
Joseph C. Shields
A large fraction of nearby galaxies exhibit AGN-like activity at weak levels as traced by optical emission-line properties. I will present new results from Hubble Space Telescope spectroscopic surveys that address the extent to which this activity actually derives from accretion-powered phenomena. For objects that clearly are accretion-powered, these results have important bearing on the physics of accretion in low-power sources.
02/26/02
Shlosman Isaac JILA, University of Colorado at Boulder
JILA, Univ. of Colorado, Campus Box 440
CO 80309-0440 Boulder, USA
Presentation 1 : Invited
TBA
Isaac Shlosman
02/28/02
Siemiginowska Aneta Harvard-Smithsonian Center for Astrophysics
60 Garden Street, MS-4
02138 Cambridge, MA, USA
Presentation 1 : Poster
First Chandra Images of GPS and CSS sources: Do GPS/CSS sources exhibit intermittent activity?
Aneta Siemiginowska
Giga-Hertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) (see O'Dea 1998 for review) sources are known to have compact radio morphology ($<$~1kpc-10kpc respectively). They have been interpreted as either young counterparts of FR I radio galaxies or as ``frustrated'' AGN, in which the radio jets are not able to penetrate the host galaxy's gas and dust. There are just a few examples of GPS galaxies with a very faint Mpc scale radio structures, which are interpreted as relics of past activity in the source. Only a small sample of GPS/CSS source were observed with low resolution X-ray telescopes before Chandra, indicating that associated intrinsic absorption could be present in some sources. The high spatial resolution of Chandra allows us to study the environment of these sources within arcsec from the strong compact core. Thus far we have detected $\sim 30$ arcsec X-ray jets in two sources and faint X-ray emission within 10 arcsec of the core. Five more sources are scheduled for Chandra observations before May and we plan to include them in our presentation. Our goal is to study the extended emission associated with the GPS/CSS core in search of signatures of their intermittent activity. We will discuss implications of our current observations and possible theoretical scenarios for the intermittent activity of these sources including disk instabilities and feedback mechanism also considered recently for radio sources in clusters.
12/04/01
Sikora Marek N. Copernicus Astronomical Center
Bartycka 18
00-716 Warsaw, Poland
Presentation 1 : Invited
Learning about Jets from Observations of Blazars
Marek Sikora
Jets, paving their way outward through the inner regions of active galaxies, Compton-interact with the radiation from an accretion flow and with the reprocessed/rescattered fraction of that radiation in the broad emision line region and in the dusty environment of the molecular tori. The presence or absence of spectral signatures associated with the radiative effects of these interactions is used to determine the physical parameters and provide constraints on the structure of jets near their bases.
02/27/02
Sol Helene Observatoire de Paris
Place J. Janssen
92195 Meudon, France
Presentation 1 : Invited
Active galactic muclei at very high angular resolution
Sol, H., Woillez, J., Lai, O., Perrin, G.
Since many years, VLBI technics allow to explore AGN structures at the milliarcsecond scale in the radio range. This provided a wealth of information mainly on the jet physics, and on some circumnuclear disks. The present decade is now allowing a zooming towards AGNs in the infrared and optical ranges. The advent of large interferometers (VLTI, KIIA) at these wavelengths will soon open a new window on compact cores, accretion and ejection features, dust content, stellar environnement, and interconnection between these constituents. In the northern hemisphere, the OHANA project of interferometry between large telescopes of the Mauna Kea will combine the highest sensibility with the highest angular resolution (o.2 milliarcsecond in the J band). We will illustrate how confrontation of simple models of nuclear jets, broad line regions, circumnuclear disks and starbursts to expected interferometric parameters can constrain AGN physics.
Presentation 2 : Poster
Multispectral variability of blazars
K. Katarzynski, H. Sol, A. Kus
Torun Center for Astronomy (Poland) and Observatoire de Paris (France)
Analysis of the temporal evolution of particle populations and of radiation tranfer along relativistic jets allows us to generate light curves of blazars at different frequencies. In our modelling, stationary emission from radio to X-rays is due to the synchrotron radiation of relativistic electrons ejected from the central engine in an inhomogeneous VLBI jet. Variability and flares are due to evolving synchrotron and Inverse-Compton radiation of additional compact components (blob or shock) travelling along the jet. We consider two scenarios for the highly energetic particles of compact components, which are either injected from the central engine, or accelerated in situ. The model can explain connection between variability observed from the radio to the X-rays frequencies, and predicts also possible correlation with very high energy gamma ray flares. New data obtained for Mrk421 in 2001 show a flare in the radio range (at 2.7 and 5 GHz) correlated with a X-ray flare observed by RXTE. We show how the acceleration scenario well describes the temporal evolution of such multispectral flare.
03/01/02
Spinoglio Luigi Istituto di Fisica dello Spazio Interplanetario CNR
Via Fosso del Cavaliere 100
I-00133 Roma, Italy
Presentation 1 : Poster
Seyfert and starburst galaxies in the Local Universe and beyond: from ISO observations to predictions for future space missions
Luigi Spinoglio, Paola Andreani, Matthew Malkan
ISOPHOT photometry is presented for 90 objects (29 Seyfert 1's, 35 Seyfert 2's, 12 starburst galaxies and 14 normal galaxies for comparison), all belonging to the 12 micron galaxy sample. Color-color diagrams and spectral energy distributions are defined using the ISO and the IRAS data. The 60-200 micron SED can be fitted with thermal dust emission at two temperatures (one cold at 15-30K and one warm at 50-70K), with a dust emissivity law proportional to the inverse square of the wavelength. A mild anti-correlation is found between the [200 - 100] color and the "60 micron excess". We infer that galaxies with a strong starburst component, and thus a strong 60 micron flux, have a steeper far-infrared turnover. In non-Seyfert galaxies, increasing the luminosity corresponds to increasing the star formation rate, that enhances the 25 and 60 micron emission. The spectral energy distributions measured by ISO and IRAS in the Local Universe are used to make predictions on the energy distributions at various redshifts for Seyfert and starburst galaxies for the next infrared and submillimeter space missions SIRTF and Herschel. The number of galaxies that could be detected in deep far-IR surveys are also predicted.
Presentation 2 : Poster
Mid- and far-infrared spectroscopy of Seyfert galaxies
Luigi Spinoglio, Matt Malkan, Howard Smith, Jackie Fischer
Infrared line ratio diagrams are a powerful tool to distinguish the different emission components in galaxies. We will focus on two particular examples: The ISO LWS diagram showing the [CII]158um/[OI]63um ratio versus the [OIII]88um/[OI]63um ratio is able to separate AGNs from starburst and PDR emission. The ISO SWS diagram with the [NeVI]7.6um/[OIV]26um ratio versus the [NeV]14um/[NeV]24um ratio is a good tracer of both the ionization potential and the density in the extreme conditions of AGNs, as is shown from photoionization models. Finally the complete mid- to far-IR spectrum of the prototype Seyfert 2 galaxy NGC1068 is shown and discussed.
12/05/01
Storchi-Bergmann Thaisa Instituto de Fisica - UFRGS
Av. Bento Goncalves 9500, Campus do Vale
91501-970 Porto Alegre, Brasil
Presentation 1 : Poster
The accretion disk in the nucleus of NGC1097: constraints from 10 yrs of observations
Thaisa Storchi-Bergmann, Rodrigo Nemmen da Silva & M. Eracleous
We have observed the nuclear spectrum of NGC1097 more than once a year from 1991 to 2001. We show the evolution of the broad double-peaked Halpha profile over this period of time, which sets a number of constraints on the accretion disk model previously proposed. Based on the model fits, we present a physical scenario for the evolution of the double-peaked profile.
09/14/01
Svensson Roland SCFAB, Stockholm Observatory
Roslagsbacken 21
SE-106 91 Stockholm, Sweden
02/14/02
Tagger Michel Service d'Astrophysique, CEA Saclay
SAp, CEA Saclay
91191 Gif sur Yvette, France
Presentation 1 : Poster
The Accretion-Ejection Instability in magnetized disks: from microquasars to AGN
M. Tagger, P. Varnière and J. Rodriguez
We will summarize theoretical and numerical results on the physics of the Accretion-Ejection Instability, which forms in the central region of magnetized disks. It has the unique property that it grows by extractingenergy and angular momenum form the disk (causing accretion) and emitting them upward as Alfven waves to the corona, where it could thus feed a wind or a jet. We will then present new observational results showing that it is a good candidate to explain the l ow-frequency Quasi-Periodic Oscillation of microquasars, and discuss how this coul apply to the central engine of AGNs.
02/17/02
Terashima Yuichi Univ. of Maryland and ISAS
Astronomy Dept, Univ. of Maryland
20742 College Park, USA
Presentation 1 : Poster
Chandra Snapshot Observations of Low-Luminosity AGNs with a Compact Radio Source
Y. Terashima & A.S. Wilson
We present the results of Chandra snapshot observations of LINERs (Low-Ionization Nuclear Emission-line Regions) and low-luminosity Seyfert galaxies. Our sample consists of all the objects with a flat or inverted spectrum compact radio core in the VLA survey of low-luminosity AGN (LLAGN) candidates by Nagar et al. (2000). An X-ray nucleus is detected from all objects except one and their X-ray luminosities are in the range 5e38 to 8e41 ergs/s. X-ray to Halpha luminosity ratios of most objects are in good agreement with the correlation known for LLAGNs and more luminous AGNs, and indicate that their optical emission lines are predominantly powered by a LLAGN. A few objects are fainter in X-rays than the correlation. Comparing with multi-wavelengths results, we find that these objects are most likely to be heavily obscured AGN. We show at least a part of type 2 LINERs are a low-luminosity counter part of an obecured AGN which are often observed in Seyfert 2s galaxies. We compare the radio to X-ray spectral slope of LLAGNs with those of more-luminous AGNs, and confirm the suggestion based on optical studies that a large fraction of LLAGNs are radio loud.
01/18/02
Thatte Niranjan Max-Planck-Institut fuer extraterrestrische Physik
Giessenbachstrasse 1
D-85748 Garching, Germany
Presentation 1 : Poster
High spatial resolution near infrared spectroscopy of the nuclear region of NGC 1068
N. Thatte, R. Genzel, R. Davies, R. Maiolino, M. Tecza
We present near infrared spectra of the nuclear region of the prototypical Seyfert 2 galaxy NGC 1068, taken with the Keck NIRSPEC spectrograph assisted by the Keck A.O. system. The spatially and kinematically resolved structure of the Si VI coronal line emission, together with integral field data from the MPE 3D spectrograph (Si VI and Fe II emission lines), provides clues to the kinematics of the coronal and narrow line regions. We propose a cartoon model of the inner NLR which explains the new observations.
Presentation 2 : Poster
SINFONI: An adaptive optics assisted integral field spectrograph for the VLT
The SINFONI Instrument team (ESO and MPE)
SINFONI will provide integral field spectroscopic capabilities at near infrared wavelengths, at spatial resolutions close to the diffraction limit of the ESO VLT (~50 milli arcseconds). It is scheduled to commence routine operation in early 2004. We present an overview of the instrument's capabilities, and highlight its potential contributions to in-depth studies of the central regions of nearby active galactic nuclei.
10/02/01
Torricelli Guidetta Osservatorio di Arcetri
Largo E.Fermi 5
50125 Firenze, Italy
Presentation 1 : Poster
NON THERMAL EMISSION FROM AGN DISK CORONAE
G.Torricelli-Ciamponi, A.Orr, P.Pietrini
Hot accretion disk coronae may account for substantial X-ray flux in AGN.. We present the results from a novel coronal emission model which builds upon the knowledge we have of solar-stellar coronae. The model considers a population of non-thermal relativistic electrons (injected at the top of an accretion disk magnetic loop) and computes the emission due to the relevant physical mechanisms. The results are compared with the X-ray spectrum of AGN's observed by BeppoSAX. The constraints on model parameters are discussed.
02/21/02
Tran Hien Johns Hopkins University
Dept. of Physics & Astronomy
21218 Baltimore, MD, USA
Presentation 1 : Poster
The Unified Model & Evolution of Active Galaxies: Are All Seyfert 2 Gal axies Created Equal?
Hien D. Tran
The AGN unified model proposes that Seyfert 2 (S2) galaxies are basically the same class of object as Seyfert 1 (S1) galaxies but viewed from a different direction. Direct evidence supporting this picture came from spectropolarimetric observations that showed broad, polarized permitted lines in many S2s, indicating that the broad-line region (BLR) characteristic of S1 is obscured from direct view, visible only in reflected light. Many other S2s, however, failed to show any signs of broad emission lines in their polarized flux spectra, suggesting that either the BLR could not exist, or other extranuclear factors (obscuration, starburst, geometry...) had rendered the polarization signals too weak to be detectable. Based on the analysis of a large spectropolarimetric survey of S2s from the CfA and 12 micron samples conducted at Lick, Palomar and Keck Observatories, we present evidence supporting the contention that S2s with hidden BLR (HBLRs) are intrinsically more powerful than non-HBLR S2s. The positive detection of BLR in HBLR S2s appears to be due largely to the intrinsic strength of the hidden AGN nucleus rather than the lower level of nuclear obscuration or reduced dominance of circumnuclear starburst. When the intrinsic difference between HBLR and non-HBLR S2s is taken into account, it is shown that the former share many similar large-scale characteristics with Seyfert 1 galaxies, as would be expected if the unified model is correct, while the latter do not. The incidence of HBLR is also found to have a tendency to increase with AGN strength, suggesting a temporal development of the obscuring torus opening angle. Thus, not all Seyfert 2 galaxies are intrinsically similar in nature, and we speculate that evolutionary processes may be at work.
02/27/02
Treves Aldo Universita' dell'Insubria
via Valleggio 11
22100 Como, Italy
Presentation 1 : Poster
BL Lac objects mass from the stellar velocity dispersion of the host galaxy.
A. Treves, R. Falomo, N. Carangelo, J. K. Kotilainen
We report on measurements of stellar velocity dispersion (sigma) for a dozen of low redshift BL Lac host galaxies. Observations were performed in 2001-2002 using the 2.5m Nordic Optical Telescope in the north and the ESO 3.6m telescope for southern sources. The derived values of sigma are found in the range 150 to 300 km/s, similar to that measured for inactive luminous ellipticals. We use the correlation between sigma and the central black hole mass (MBH) recently established for nearby early type galax ies (Gebhardt et al 2000; Ferrarese and Merritt 2000) to derive the BH mass of our targets. The corresponding values of BH masses for the observed sample of BL Lacs is between 5x10^7 and 10^9 solar masses. These values are compared with those deriving from the host galaxy luminosity - MBH relation.
02/25/02
Urry Meg Space Telescope Science Institute
3700 San Martin Drive
21218 Baltimore, MD, USA
Presentation 1 : Poster
Black Hole Masses in AGN
Meg Urry and Jong-Hak Woo
02/26/02
Uttley Phil University of Southampton
Dept. of Physics and Astronomy, University of Southampton
SO17 1BJ Southampton, UK
Presentation 1 : Poster
Partly cloudy skies in NGC3227: catching an absorption event with RXTE
P. Uttley, G. Lamer, I. M. McHardy
Long term monitoring of Seyfert galaxies with RXTE allows us to probe X-ray spectral variability on an unprecedented range of time-scales. In NGC3227, increases in the hardness of the continuum are anticorrelated with flux, as seen in other AGN. However, in early 2001 we witnessed a strong rise then decline in hardness over the course of 3 months, which showed no simple relation to flux changes. The uniqueness and symmetry of this event suggest that we have witnessed the transit of an absorbing cloud across the line of sight to the source. Using spectral and dynamical constraints, we argue that the cloud lies in the broad line region. Future multi-band observations of such an event may allow us to determine the detailed composition of BLR clouds.
Presentation 2 : Poster
Non-linearity and low `states' in AGN: two sides of the same coin
P. Uttley, I. M. McHardy, S. Vaughan
Non-linearity in X-ray lightcurves of ultrasoft/NLS1 galaxies has been suspected for some time, but not proven. Recently, long-term X-ray monitoring observations of the NLS1 NGC4051 showed that besides showing possible evidence for non-linearity, the source also shows distinctive low-flux, low-variability `states' which last for months at a time. Here we show that both non-linearity and low states are a direct outcome of the remarkable linear relationship between RMS variability and flux which holds in lightcurves of AGN and X-ray binaries: AGN and XRB lightcurves are intrinsically non-linear, and can show low-states if the variability on all time-scales is large. We discuss physical interpretations of this result.
02/28/02
van der Meer Rob L.J. SRON (Space Research Organisation Netherlands)
Sorbonnelaan 2
3584 CA Utrecht, The Netherlands
Presentation 1 : Poster
NGC 4051: Time variability in high resolution Chandra X-ray spectra.
R.L.J. van der Meer, J.S. Kaastra, K.C. Steenbrugge, S. Komossa
We present the analysis of the Chandra LETGS spectra of NGC 4051. The Narrow-line Seyfert 1 galaxy NGC 4051 has been intensively studied and is known to contain a warm absorber. The recent Chandra LETGS spectrum shows rapid variations with changes of a factor of 10 in flux. The long term variability is shown by comparing the spectrum with the HETGS spectrum taken a year earlier. From the HETGS spectrum a velocity component of -2340 km/s (blueshift) was found. The new LETGS spectrum does not show this component, but shows instead a new velocity component with almost double this speed. We draw conclusions on the dynamic constraints posed by these velocities and velocity changes.
12/11/01
Vanzi Leonardo ESO - European Southern Observatory
Alonso de Cordova 3107
0 Santiago, Chile
Presentation 1 : Poster
A Multy Wavelength Study of IRAS 19254-7245 - The Superantennae
L. Vanzi et al.
We present observations in the optical, near-infrared and millimetre of the Ultraluminous Infrared Galaxy IRAS 19254-7245, also known as The Superantennae. The galaxy is an interacting system with a double nucleus and long tails extending for about 350 Kpc. We study in details the southern component of the system which is optically classified as a Sy2 galaxy.
02/17/02
Veilleux Sylvain Univ. of Maryland
Astronomy Dept, Univ. of Maryland
20742 College Park, USA
Presentation 1 : Invited
The AGN Paradigm: Radio-Quiet Objects
Sylvain Veilleux, University of Maryland
The current paradigm for radio-quiet AGNs is reviewed taking into account new results from recent large-scale surveys with ground-based facilities and space missions. Topics include demography as a function of type, black hole mass, structure of the central engine, relationship with the host galaxy, and fueling/triggering processes. Dependences on AGN power and lookback time are pointed out throughout the discussion.
09/03/01
Verdoes Kleijn Gijs Leiden Observatory
Sterrewacht Leiden, Postbus 9513
2300 RA Leiden, The Netherlands
Presentation 1 : Poster
Black holes and nuclear gas and dust in nearby active and quiescent galaxies.
G. Verdoes Kleijn (1), J. Noel-Storr (1,2), S. Baum (1), R. van der Marel (1), P.T. de Zeeuw (3), C. O'Dea (1), J. van Gorkom (2)
(1): STScI (2): Columbia University (3): Leiden Observatory
Nuclear dust and neutral and ionized gas is present in the cores of many nearby active and quiescent early-type galaxies. The properties which are decisive in triggering nuclear activity and the origin and ionization mechanism of the interstellar material are not well known. To address these issues an overview is presented of results from radio and HST optical imaging and spectroscopic observations for a sample of 21 nearby radio galaxies, the `UGC FR I sample'. Constraints on the origin and Doppler boosting of AGN emission from correlations between broad- and narrowband AGN emission are described as well as the relative orientation of central dust features, galaxies and radio-jets. Gas kinematics for the sample and dynamical modeling of gas disks to determine central black hole (BH) masses are presented and the validity and accuracy of the gas dynamical method to derive BH masses in comparison to other methods to obtain BH masses is discussed. These results are then compared to those for nearby quiescent and radio-quiet active nuclei in other early-type galaxies. This allows us to determine relationships between the level of nuclear activity on the one hand and host and gas disk properties and BH mass on the other hand. The constraints placed by these on the triggering mechanism for activity and origin and ionization mechanism of interstellar matter in the nuclei of nearby early-type galaxies are discussed.
11/09/01
Véron Mira Observatoire de Haute Provence
Observatoire de Haute Provence
04870 Saint-Michel l'Observatoi, France
11/09/01
Véron Philippe Observatoire de Haute Provence
Observatoire de Haute Provence
04870 Saint-Michel l'Observatoi, france
12/31/01
Wada Keiichi National Astronomical Observatory of Japan
Osawa 2-21-1
181-8588 Mitaka, Japan
Presentation 1 : Poster
Obscuring Material around the Central Engine with Starbursts
Keiichi Wada, Colin Norman
The structure of obscuring matter in the environment of active galactic nuclei with associated nuclear starbursts is investigated using 3-D hydrodynamical simulations. Simple analytical estimates suggest that the obscuring matter with energy feedback from supernovae has a torus-like structure with a radius of several tens of parsecs and a scale height of $\sim 10$ pc. These estimates are confirmed by the fully non-linear numerical simulations, in which the multi-phase inhomogeneous interstellar matter and its interaction with the supernovae are consistently followed. The globally stable, torus-like structure is highly inhomogeneous and turbulent.
08/29/01
Wagner Stefan LSW
Koenigstuhl
69117 Heidelberg, Germany
Presentation 1 : Poster
Structure and Nonthermal Radiation Processes in radio-loud Quasars: A European network on multifrequency monitoring and jet physics
Multifrequency monitoring is an essential tool to understand the radiation mechanism producing the broad-band non-thermal spectra of radio-loud AGN, constrain models of particle acceleration and jet structure on a sub-pc scale. To facilitate studies which are very demanding in observing resources, a TMR network on `Structure and Radiation Processes of Quasars from Multifrequency Monitoring' has been started, incorporating the development of novel observing approaches, multifrequency studies with the new generation of high-energy instruments, and theoretical research on acceleration and radiation processes. The current status and future plans are summarized.
08/28/01
Wamsteker Willem ESA-VILSPA
P.O.Box 50727
28080 Madrid Spain
Presentation 1 : Poster
WSO/UV and Active Galaxies
Willem Wamsteker for the WSO/UV Implementation Committee (WIC)
The World Space Observatory is an unconventional space project proceeding via distributed studies. The present design, verified for feasibility, and currently entering Phase A, consists of a 1.7-meter telescope operating at the second Largangian point of the Earth-Sun system. The focal plane instruments consist of three UV spectrometers covering the spectral band from Lyman alpha to the atmospheric cutoff with R~55,000 and offering long-slit capability over the same band with R~1,000. In addition, a number of UV and optical imagers view adjacent fields to that sampled by the spectrometers. Their performance compares well with that of HST/ACS and the spectral capabilities of WSO rival those of HST/COS. We will indicate the importance of WSO to AGN research, especially to clarify the enigma of the processes taking place in the BLR. The importance of such a mission which can coordinate with observing capabilities at other wavelengths (especially the X-ray domain) is highlighted. The WSO/UV, as presently conceived, will be constructed and operated with a distributed philosophy. This will allow many groups and countries to participate, each contributing as much as feasible but allowing multi-national participation. Although designed originally with a conservative approach, the WSO embodies some innovative ideas and will allow a world-class mission to be realized with a moderate budget.
02/14/02
Wandel Amri The Hebrew University
Givat Ram
91904 Jerusalem, Israel
Presentation 1 : Poster
Massive Black Holes in Active and Quiescent Galaxies
A. Wandel
Massive Black Holes detected in the centers of many nearby galaxies show an approximately linear relation with the luminosity of the host bulge, with the black hole mass being 0.001-0.002 of the bulge mass. We show that massive BHs of AGNs (Seyfert galaxies and quasars, measured by reverberation mapping) follow the same BH-bulge relation as ordinary (inactive) galaxies (Wandel 2002, ApJ 565 762). Narrow line AGN may have a significantly lowe BH/bulge ratio. This fraction is comparable with the fraction of mass in black holes deduced from integrated quasar light, indicating that BHs in ordinary galaxies were formed during an active past, by the accretion of the same matter that fuelled the former active nucleus. Further correlations observed between properties of AGNs and their host galaxies support this scenario.
Presentation 2 : Poster
The Black-Hole - Stellar velocity Relation in AGN
A.Wandel, L.Ferrarese, D.Merrit B.M.Peterson and R.W.Pogge
Massive Black Holes detected in the centers of nearby galaxies show a tight relation with the stellar velocity dispersion v* in the host bulge. Combining existing data, new observations and extrapolation schemes based on the Faber-Jackson relation, a BH mass vs.v* in AGNs is constructed.
08/30/01
Wiita Paul Georgia State University
Department of Physics and Astronomy
30303-3083 Atlanta GA, USA
Presentation 1 : Invited
Radio galaxies and the star formation history of the universe
Gopal-Krishna and Paul J. Wiita
Gopal-Krishna will submit the abstract as the invited speaker.
11/12/01
Wilson Andrew University of Maryland
Astronomy Department
MD 20742 College Park, U.S.A.
Presentation 1 : Oral
Chandra X-ray Studies of Extended Structure in Active Galaxies
Andrew S. Wilson
I will summarise selected results from a program of imaging spectroscopy with Chandra on about 20 nearby, bright Seyfert galaxies, radio galaxies and low luminosity AGN.
10/18/01
Wlerick Gérard Observatoire de Paris
Place J. Janssen
92195 MEUDON, FRANCE
10/08/01
Woillez Julien Observatoire de Paris - DAEC/DESPA
5, place Jules Janssen
92195 MEUDON, FRANCE
08/29/01
Worrall Diana University of Bristol
Physics Dept, Tyndall Avenue
BS8 1TL Bristol, United Kingdom
Presentation 1 : Poster
The X-ray Emission of Low-Power Radio Galaxies
D.M. Worrall, M. Birkinshaw, M.J. Hardcastle University of Bristol
Our Chandra survey of the B2 bright sample finds low-power radio galaxies to have galaxy-scale atmospheres and a compact, largely unabsorbed X-ray core. Cluster-scale gas, known to be present from ROSAT, appears as structureless background in our high-resolution images. We find kpc-scale X-ray jet emission to be common. Deep Chandra mapping of the brightest low-power radio galaxies now makes possible the detailed study of their physics. We present evidence that jet X-rays have a synchrotron origin, and address issues of particle acceleration and bulk speed.
08/28/01
Wozniak Herve Laboratoire d'Astrophysique de Marseille
2, Place Leverrier
13248 Marseille cedex 4, France
Presentation 1 : Poster
We present an interpretation of the stellar velocity dispersion drops discovered in the nuclear regions of three galaxy hosts of active galactic nuclei (NGC1097, NGC1808 and NGC5728) by Emsellem et al. (2001). Using self-consistent N-body simulations including stars, gas and star formation, we show that young stars born in the nuclear regions from dynamically cold gas have a lower velocity dispersion than the older stellar population. Moreover, the young population (less than 0.9 Gyr old in our models), being more massive and brighter than the older one at near infrared wavelengths, fully dominates the observed line-of-sight kinematics of the circum-nuclear regions.


Presentation 2 : Poster
TBD

09/11/01
Yaqoob Tahir Johns Hopkins University, USA/ NASA, GSFC
Dept. of Physics and Astronomy, 3400 N. Charles St.
MD21218 Baltimore, USA
Presentation 1 : Poster
Chandra Grating Observations of AGN
T. Yaqoob, B. McKernan, I. M. George, T. J. Turner
We present the results of five new Chandra grating observations of AGN, some of which were performed simultaneously with other missions such as RXTE, and HST. We discuss the origin and physics of the absorption and emission features and compare and contrast the properties of the AGN in the sample, from these new, and archival observations. In particular we discuss the implications of the features found in the soft X-ray band, and the origin of the iron K lines.
08/30/01
Yusef-Zadeh Farhad Northwestern University
Dept Physics and Astronomy, 2145 Sheridan Road
60208 Evanston, US
Presentation 1 : Poster
High Energy Activity in the Nucleus of the Galaxy
F. Yusef-Zadeh
Recent observations of the Galactic center using Chandra and ASCA have provided a number of interesting thermal and nonthermal X-ray sources within the inner degree of the Galactic center. I will review recent results of these observations and discuss which X-ray source is likely to be associated with with 3EGJ1746--2851, a steady source of high energy emission lying within 0.2degrees of the Galactic center.
02/28/02
Zhang You Hong Dipartimento di Scienze, Universita' dell'Insubria
via Valleggio 11
I-22100 Como, Italy
Presentation 1 : Poster
On the X-ray time lags of TeV blazars
Zhang Y.H., Treves, A., et al.
The three famous TeV blazars, i.e., Mrk 421, Mrk 501 and PKS 2155-304, show violent variability in the X-rays. We will discuss the important issue regarding the variability, i.e., the inter-band X-ray time lags of these sources. Recent long-look and intensive monitoring of these sources with ASCA, BeppoSAX, RXTE and XMM-Newton have revealed that the X-ray time lags are variable from flare to flare. Both the soft and hard lags have been found to be energy-dependent. These discoveries impose strong implications on the acceleration and cooling mechanism of the relativistic electrons responsible for the observed X-ray emission. We will also discuss how the interplay between the acceleration, injection and synchrotron cooling time may interpret the observed variations of the time lags and their energy-dependence, from which the parameters of the emitting region are constrained. The evolution of the X-ray time lags in TeV blazars are explored on the basis of the internal shock models taking place in the blazar jets.
02/22/02
Zycki Piotr Copernicus Astronomical Center
Bartycka 18
00-716 Warsaw, Poland
Presentation 1 : Poster
Simulaneous Chandra/XTE observations of the bright Seyfert 2 galaxy NGC 4945
Piotr Zycki, Greg Madejski, Chris Done
The central X-ray source of NGC 4945 is obscured by an absorber with optical thickness about 2. The X-ray flux varies on time scale of less than a day which implies that the absorber is not a torus but a much thinner structure. Chandra observations reveal in greater detail than ever before the structure of the inner region on scale of tens of parsecs.
Presentation 2 : Poster
Fourier-frequency resolved X-ray spectroscopy as a tool for constraining the geometry of accretion
Piotr Zycki
I am going to demonstrate how the Fourier-frequency resolved spectroscopy can constrain possible models of accretion flow onto black holes both in AGN and black hole binaries. In particular, distringuishing between scenarios invoking truncated and un-truncated accretion disks appear to be possible.