Presentation 1 : Oral
Spectral resolution effects (R=200 to 15000) in galaxy evolution.
Damien Le Borgne, Brigitte Rocca-Volmerange
Spectral resolution is a fundamental parameter for spectral synthesis.
We propose to investigate its role in two different domains such as photometric redshifts and metallicity evolution.
Low spectral resolution (R<200) is sufficient to estimate accurate
photometric redshifts, when age constraints are respected
(Le Borgne & Rocca-Volmerange, 2002).
An increased resolution would make easier the estimates by minimizing the photometric band number.
High spectral resolution (R>10000) gives measurements of metallicity and velocity dispersion parameters, required to determine ages and structural properties of galaxies.
Synthetic evolution models built to follow these parameters are generally using libraries with metallicity effects but unsufficient resolution (Kurucz, 1996, Lejeune, 1997).
They are limitated to results from extended stellar energy distributions.
Models with stellar libraries taking into account metallicity
and with significant spectral resolution are urgently required by the
next generations of high resolution spectrographs installed on 10m telescopes.
An high-resolution evolutionary code PEGASE-HR is built (Le Borgne, Fioc, Lancon, Prugniel, Rocca-Volmerange, Soubiran, in preparation) by linking our model PEGASE (http://www.iap.fr/pegase) to the high resolution (R=15000) stellar library ELODIE observed at 193/OHP.
The sensitivity of this new model to interpret hydrogenic and metallic
lines H$\alpha$, H$\beta$, H$\gamma$, Fe, Mg, and Na is exceptional and allows to solve many degenaracies such as the well known age-metallicity one.