[Show abstract][Hide abstract] ABSTRACT: We select far-infrared (FIR: 60 μm) and far-ultraviolet (FUV: 530 Å) samples of nearby galaxies in order to discuss the biases encountered by monochromatic surveys (FIR or FUV). Very different volumes are sampled by each selection, and much care is taken to apply volume corrections to all the analyses. The distributions of the bolometric luminosity of young stars are compared for both samples: they are found to be consistent with each other for galaxies of intermediate luminosities, but some differences are found for high (>5 × 1010 L☉) luminosities. The shallowness of the IRAS survey prevents us from securing a comparison at low luminosities (<2 × 109 L☉). The ratio of the total infrared (TIR) luminosity to the FUV luminosity is found to increase with the bolometric luminosity in a similar way for both samples up to 5 × 1010 L☉. Brighter galaxies are found to have a different behavior according to their selection: the LTIR/LFUV ratio of the FUV-selected galaxies brighter than 5 × 1010 L☉ reaches a plateau, whereas LTIR/LFUV continues to increase with the luminosity of bright galaxies selected in FIR. The volume-averaged specific star formation rate (SFR per unit galaxy stellar mass, SSFR) is found to decrease toward massive galaxies within each selection. The mean values of the SSFR are found to be larger than those measured for optical and NIR-selected samples over the whole mass range for the FIR selection, and for masses larger than 1010 M☉ for the FUV selection. Luminous and massive galaxies selected in FIR appear as active as galaxies with similar characteristics detected at z ~ 0.7.
Full-text · Article · Dec 2008 · The Astrophysical Journal Supplement Series
[Show abstract][Hide abstract] ABSTRACT: We compare the dust attenuation properties of two samples of galaxies purely selected in the Galaxy Evolution Explorer (GALEX) near-ultraviolet band (NUV; 1750-2750 Å, λmean = 2310 Å) and in the far-infrared (FIR) at 60 μm. These samples are built using the GALEX and IRAS sky surveys over ~600 deg2. The NUV-selected sample contains 95 galaxies detected down to NUV = 16 mag (AB system). Eighty-three galaxies in this sample are spiral or irregular, and only two of them are not detected at 60 μm. The FIR-selected sample is built from the IRAS PSCz survey, which is complete down to 0.6 Jy. Among the 163 sources, we select 118 star-forming galaxies that are well measured by IRAS; all but one are detected in NUV, and 14 galaxies are not detected in the far-ultraviolet band (FUV; 1350-1750 Å, λmean = 1530 Å). The dust-to-ultraviolet (NUV and FUV) flux ratio is calibrated to estimate the dust attenuation at both wavelengths. The median value of the attenuation in NUV is found to be ~1 mag for the NUV-selected sample, versus ~2 mag for the FIR-selected one. Within both samples, the dust attenuation is found to correlate with the luminosity of the galaxies. Almost all the NUV-selected galaxies and two-thirds of the FIR-selected sample exhibit a lower dust attenuation than expected from the tight relation found previously for starburst galaxies between dust attenuation and the slope of the ultraviolet continuum. The situation is reversed for the remaining third of the FIR-selected galaxies: their extinction is higher than that deduced from their FUV - NUV color and the relation for starbursts.
Full-text · Article · Dec 2008 · The Astrophysical Journal