The VIMOS Ultra Deep Survey: Lyα Emission and Stellar Populations of Star-Forming Galaxies at 2 < z < 6

Abstract

AbstractThe extensive ground-based spectroscopy campaign from the VIMOS Ultra-Deep Survey (VUDS), and the deep multi-wavelength photometry in three very well observed extragalactic fields (ECDFS, COSMOS, VVDS), allow us to investigate physical properties of a large sample (~4000 galaxies) of spectroscopically confirmed faint (iAB ≲ 25 mag) SFGs, with and without Lyα in emission, at z ~ 2–6. The fraction of Lyα emitters (LAEs; equivalent width (EW) ≥ 20Å) increases from ~10% at z ~ 2 to ~40% at z ~ 5–6, which is consistent with previous studies that employ higher Lyα EW cut. This increase in the LAE fraction could be, in part, due to a decrease in the dust content of galaxies as redshift increases. When we compare best-fit SED estimated stellar parameters for LAEs and non-LAEs, we find that Es(B-V) is smaller for LAEs at all redshifts and the difference in the median Es(B-V) between LAEs and non-LAEs increases as redshift increases, from 0.05 at z ~ 2 to 0.1 at z ~ 3.5 to 0.2 at z ~ 5. For the luminosities probed here (~L*), we find that star formation rates (SFRs) and stellar masses of galaxies, with and without Lyα in emission, show small differences such that, LAEs have lower SFRs and stellar masses compared to non-LAEs. This result could be a direct consequence of the sample selection. Our sample of LAEs are selected based on their continuum magnitudes and they probe higher continuum luminosities compared to narrow-band/emission line selected LAEs. Based on our results, it is important to note that all LAEs are not universally similar and their properties are strongly dependent on the sample selection, and/or continuum luminosities.