Presentation 1 : Oral
Statistical Properties and Abundance Measurements of Sub-DLAs. (PNC)
Celine Peroux, Miroslava Dessauges-Zavadsky, TaeSun Kim, Richard McMah
abstract1 -- QSO absorbers constitute powerful observational tools to measure the
cosmological evolution of the neutral gas mass and metals. At z<3.5,
90% of the HI mass is in damped Ly-alpha systems (DLAs). But it has
been suggested that at z>3.5, 45% of the HI lies in systems below the
traditional DLA definition, in ``sub-DLAs'' with 10^19 < N(HI) < 2 *
10^20 cm^-2. We take advantage of the ESO-UVES archive quasar spectra
to build a homogeneous sample of sub-DLAs. These data are used to
measure the sub-DLA number density redshift evolution and to directly
establish the column density distribution function down to N(HI) =
10^19 cm^-2. Detailed metal abundance analyses of this class of
absorbers are also made in order to compare with the characteristics
of the well studied DLAs.
Presentation 2 : Oral
Outflows in Galaxies and DLAs. (PNG)
Celine Peroux
Although quasar absorbers, and in particular Damped Lyman-alpha
systems (DLAs) have proven a valuable tool to study galaxies at
high-redshifts, their exact nature is so far poorly constrained. In
this context, it has been suggested that outflows in galaxies might
account for at least part of the DLA population. Observational
evidences and models in support of this hypothesis will be reviewed,
including recent observations of Lyman Break Galaxies
(LBGs). Observational counter-arguments and theoretical limitations
will also be given. Finally, implications of such a model for the
environment of galaxies at high-redshifts will be discussed.