Herschel Detection of Dust Emission from UV-Luminous Star-Forming Galaxies at 3.3<z<4.3

We report the Herschel SPIRE detection of dust emission arising from UV-luminous (L>~L*) star-forming galaxies at 3.3 100um, suggesting dust temperatures (T_d=27-30K) significantly colder than that of local galaxies of comparable IR luminosities. The observed IR-to-UV luminosity ratio (IRX=L_IR/L_UV) is low (~3-4) compared with that observed for z~2 LBGs (IRX(z~2)~7.1+/-1.1). The correlation between the slope of the UV continuum and IRX for galaxies in the two lower luminosity bins suggests dust properties similar to those of local starburst galaxies. However, the galaxies in the highest luminosity bin appear to deviate from the local relation, suggesting that their dust properties may differ from those of their lower-luminosity and low-redshift counterparts. We speculate that the most UV luminous galaxies at this epoch are being observed in a short-lived and young evolutionary phase.