2016A&A...588A..26H

The aim of this paper is to investigate spectral and photometric properties of 854 faint (i_AB<=25mag) star-forming galaxies (SFGs) at 2<z<2.5 using the VIMOS Ultra-Deep Survey (VUDS) spectroscopic data and deep multi-wavelength photometric data in three extensively studied extragalactic fields (ECDFS, VVDS, COSMOS). These SFGs were targeted for spectroscopy as a result of their photometric redshifts. The VUDS spectra are used to measure the UV spectral slopes (β) as well as Lyα equivalent widths (EW). On average, the spectroscopically measured β (-1.36±0.02), is comparable to the photometrically measured β (-1.32±0.02), and has smaller measurement uncertainties. The positive correlation of β with the spectral energy distribution (SED)-based measurement of dust extinction Es(B-V) emphasizes the importance of β as an alternative dust indicator at high redshifts. To make a proper comparison, we divide these SFGs into three subgroups based on their rest-frame Lyα EW: SFGs with no Lyα emission (SFGN; EW<=0Å), SFGs with Lyα emission (SFGL; EW>0Å), and Lyα emitters (LAEs; EW>=20Å). The fraction of LAEs at these redshifts is ∼10%, which is consistent with previous observations. We compared best-fitSED-estimated stellar parameters of the SFGN, SFGL and LAE samples. For the luminosities probed here (∼L*), we find that galaxies with and without Lyα in emission have small but significant differences in their SED-based properties. We find that LAEs have less dust, and lower star-formation rates (SFR) compared to non-LAEs. We also find that LAEs are less massive compared to non-LAEs, though the difference is smaller and less significant compared to the SFR and Es(B-V). When we divide the LAEs according to their Spitzer/IRAC 3.6µm fluxes, we find that the fraction of IRAC-detected (m3.6<=25mag) LAEs is much higher than the fraction of IRAC-detected narrow band (NB)-selected LAEs at z≃2-3. This could imply that UV-selected LAEs host a more evolved stellar population, which represents a later stage of galaxy evolution, compared to NB-selected LAEs.