2006A&A...450...69B

We present the first large, unbiased sample of Lyman Break Galaxies (LBGs) at z∼1. Far ultraviolet-dropout (1530Å) galaxies in the Chandra Deep Field South have been selected using GALEX data. This first large sample in the z∼1 universe provides us with a high quality reference sample of LBGs. We analyzed the sample from the UV to the IR using GALEX, SPITZER, ESO and HST data. The morphology (obtained from GOODS data) of 75% of our LBGs is consistent with a disk. The vast majority of LBGs with an IR detection are also Luminous Infrared Galaxies (LIRGs). As a class, the galaxies not detected at 24µm are an order of magnitude fainter relative to the UV compared with those detected individually, suggesting that there may be two types of behavior within the sample. For the IR-bright galaxies, there is an apparent upper limit for the UV dust attenuation and this upper limit is anti-correlated with the observed UV luminosity. Previous estimates of dust attenuations based on the ultraviolet slope are compared to new ones based on the FIR/UV ratio (for LBGs detected at 24µm), which is usually a more reliable estimator. Depending on the calibration we use to estimate the total IR luminosity, β-based attenuations A_FUV are larger by 0.2 to 0.6mag. than the ones estimated from FIR/UV ratio. Finally, for IR-bright LBGs, median estimated β-based SFRs are 2-3 times larger than the total SFRs estimated as SFR_TOT = SFR_UV + SFR_IR while IR-based SFRs provide values below SFR_TOT by 15-20%. We use a stacking method to statistically constrain the 24µm flux of LBGs non individually detected. The results suggest that these LBGs do not contain large amounts of dust.