2007A&A...469...19B

The total infrared (TIR: 8-1000µm) and far-ultraviolet (FUV: ∼1500Å) luminosity functions of galaxies and the related luminosity densities ρ_TIR and ρ_FUV are known to evolve at differemt rates from z=0 to z∼1: the galaxy populations appear to be brighter in the past at both wavelengths, but the evolution in the TIR is larger than in the FUV. This leads to an increase of the ratio of TIR to FUV luminosity densities ρ_TIR/ρ_FUV which can be interpreted as a global increase of the dust attenuation from z=0 to z∼1. Our aim is to understand the origin of this increase: is it entirely due to a variation of the dust attenuation with the luminosity of the galaxies as seen as z=0 or are properties of galaxies evolving with the redshift? We focus on infrared galaxies more luminous than L_TIR=10¹¹L_☉ at z∼0.7 observed by SPITZER/MIPS and we measure their ultraviolet emission at 2310Å from GALEX images. These Luminous InfraRed Galaxies (LIRGs) represent the bulk of the TIR luminosity density at intermediate redshift. The analysis of the ratio of TIR to FUV (rest-frame) luminosity (L_TIR/L_FUV) enables us to discuss and compare their dust attenuation to that of galaxies of similar infrared luminosity selected in the same way in the nearby universe Some evolution of L_TIR/L_FUV and therefore of dust attenuation is found: LIRGs at z=0.7 span a larger range of L_TIR/L_FUV ratios than at z=0 and their mean dust attenuation at FUV wavelengths is found to be ∼0.5mag lower than for their local counterparts. The decrease of dust attenuation is found to be less than that reported in other studies for bright galaxies selected in UV rest-frame at z=1 and 2. A semi-quantitative analysis accounts for the general increase of dust attenuation with the bolometric luminosity of galaxies: it is found that the slight decrease of dust attenuation for LIRGs at z=0.7 remains consistent with the increase of ρ_TIR/ρ_FUV with redshift.