Presentation 1 : Oral
Probing the physical properties of low-luminosity galaxies at high redshifts
M. Lemoine-Busserolle, T. Contini, R. Pello, J.-F. Le Borgne, J.-P. Kneib, C Lidman
We present the preliminary results of a long-term project aiming
to derive the physical properties of high-redshift lensed galaxies,
intrinsically fainter than the Lyman break galaxies (LBG) currently observed
in the field. We thus obtained JHK ISAAC/VLT spectra of two z ~ 1.9
low-luminosity lensed galaxies (S2 and A2), located in the core of the
lensing cluster AC 114, allowing us to measure with a good signal-to-noise
ratio all the brightest rest-frame optical emission lines
([OII]3726,3728; [OIII]4959,5007; and H_alpha) which provides a
direct estimation of the SFR. An exhaustive analysis of these spectra
shows that S2 and A2 are intrinsically fainter (by 1-2 mag) and less
metal-enriched than the LBG population. Moreover, the chemical abundance
analysis reveals a very low N/O ratio in S2 comparable to what is observed
in Damped Lyman Alpha systems at z ~ 2-3. This result could indicate that
we are picking out a galaxy which has only recently condensed out of the
intergalactic midium and begun forming stars.