2007MNRAS.380..986B

Ultraviolet (UV) galaxies have been selected from the Galaxy Evolution Explorer deep imaging survey. The presence of a far-UV (FUV) drop-out in their spectral energy distributions (SEDs) proved to be a very complete (83.3 per cent) but not very efficient (21.4 per cent) tool for identifying Lyman break galaxies (LBGs) at z ∼ 1. In this paper, we explore the physical properties of these galaxies and how they contribute to the total star formation rate (SFR). We divide the LBG sample into two subclasses: red LBGs (RLBGs) detected at λ = 24µm which are mainly luminous infrared (IR) galaxies (LIRGs) and blue LBGs (BLBGs) undetected at λ = 24µm down to the MIPS/GTO limiting flux density of 83 µJy. Two of the RLBGs are also detected at 70 µm. The median SED of the RLBGs is similar (above λ ∼ 1µm) to that of a luminous dusty starburst at z ∼ 1.44, HR10. However, unlike local luminous and ultraluminous IR galaxies, RLBGs are UV bright objects. We suggest that these objects contain a large amount of dust but that some bare stellar populations are also directly visible. The median SED of the BLBGs is consistent with their containing the same stellar population as the RLBGs (i.e. a 250-500 Myr old, exponentially decaying star formation history) but with a lower dust content. The luminosity function (LF) of our LBG sample at z ∼ 1 is similar to the LF of near-UV (NUV) selected galaxies at the same redshift. The integrated luminosity densities of z ∼ 1 LBGs and NUV-selected galaxies are very consistent. Making use of the RLBG sample, we show that SFRs estimated from UV measurements and corrected using the IRX-β method provide average total SFR_TOT in agreement with the sum of the UV and IR contributions: SFR_UV+ SFR_dust. However, IRX-β-based SFR_TOT shows a large dispersion. Summing up the detected UV (1150-Å rest-frame) and IR-based SFRs of the detected objects, we find that only one-third of the total (i.e. UV + dust) LBG SFR resides in BLBGs and two-thirds in RLBGs, even though most LBGs at z ∼ 1 are BLBGs. On the other hand, the total SFR of LBGs accounts for only 11 per cent of the total SFR at z ∼ 1. Finally, we observe a regular decrease in the luminosity ratio L_dust/L_FUV from z = 0 to z ~ 2 for UV-selected samples.