IR and UV Galaxies at z = 0.6: Evolution of Dust Attenuation and Stellar Mass as Revealed by SWIRE and GALEX

We study dust attenuation and stellar mass of z similar to 0.6 star-forming galaxies using new SWIRE observations in IR and GALEX observations in UV. Two samples are selected from the SWIRE and GALEX source catalogs in the SWIRE/GALEX field ELAIS-N1-00 ( Omega = 0.8 deg super(2)). The UV-selected sample has 600 galaxies with photometric redshift (hereafter photo-z) 0.5 less than or equal to z less than or equal to 0.7 and NUV less than or equal to 23.5 (corresponding to L sub(FUV) greater than or equal to 10 super(9.6) L [unk]). The IR-selected sample contains 430 galaxies with integral of 24 mu greater than or equal to 0.2 mJy ( [unk] greater than or equal to 10 super(10.8) L [unk]) in the same photo-z range. It is found that the mean [unk]/L sub(FUV) ratios of the z = 0.6 UV galaxies are consistent with that of their z = 0 counterparts of the same L sub(FUV). For IR galaxies, the mean [unk]/L sub(FUV) ratios of the z = 0.6 LIRGs ( [unk] similar to 10 super(11) L [unk]) are about a factor of 2 lower than local LIRGs, whereas z = 0.6 ULIRGs ( [unk] similar to 10 super(12) L sub(v)) have the same mean [unk]L sub(FUV) ratios as their local counterparts. This is consistent with the hypothesis that the dominant component of LIRG population has changed from large, gas-rich spirals at z > 0.5 to major mergers at z = 0. The stellar mass of z = 0.6 UV galaxies of L sub(FUV) less than or equal to 10 super(10.2) L [unk] is about a factor of 2 less than their local counterparts of the same luminosity, indicating growth of these galaxies. The mass of z = 0.6 UV luminous galaxies (UVLGs: L sub(FUV) > 10 super(10.2) L [unk]) and IR-selected galaxies, which are nearly exclusively LIRGs and ULIRGs, is the same as their local counterparts.