Lyman Break Galaxies in the VLT/FORS2 spectroscopic campaign in the GOODS-S field

Abstract

We present initial results from our ongoing campaign of spectroscopic identifications of Lyman--break galaxies (LBGs) at z ~ 4, 5 and 6 with FORS2 at the ESO VLT. The sample of LBGs is selected from the HST/ACS images in the GOODS southern field (CDF--S), and here we discuss the spectroscopic properties of 103 LBGs that we have cofirmed in the redshift interval 3.5 < z < 6.3, of which 34 at z>5 and 27 between 5.5 and 6.3. As for LBGs at lower redshifts, we find that LBGs with LyA in emission are characterized by weaker intestellar absorption lines and bluer UV continua than galaxies whose LyA is observed in absorption. No correlation between the LyA properties and the apparent elongation of the UV morphology of the galaxies is observed, suggesting that geometrical effects are not the cause of the spectral differences. A trend of increasing LyA equivalent width with decreasing luminosity is also observed. We also present new measures of the UV luinosity function of LBGs.