Galaxy Evolution Explorer Ultraviolet Spectroscopy and Deep Imaging of Luminous Infrared Galaxies in the European Large-Area ISO Survey S1 Field

Abstract

The European Large-Area ISO Survey (ELAIS) S1 field was observed by the Galaxy Evolution Explorer (GALEX) in both its Wide Spectroscopic and Deep Imaging Survey modes. This field was previously observed by the Infrared Space Observatory, and we made use of the catalog of multiwavelength data published by the ELAIS consortium to select galaxies common to the two samples. Among the 959 objects with GALEX spectroscopy, 88 are present in the ELAIS catalog and 19 are galaxies with an optical spectroscopic redshift. The distribution of redshifts covers the range 0 < z < 1.6. The selected galaxies have bolometric IR luminosities 10 < log LIR < 13 (deduced from the 15 μrn flux using ISOCAM), which means that we cover a wide range of galaxies from normal to ultraluminous IR galaxies. The mean (σ) UV luminosity (not corrected for extinction) amounts to log λL 1530 = 9.8(0.6) L⊙ for the low-z (z ≤ 0.35) sample. The UV slope β (assuming fλx ∝ λβ) correlates with the GALEX FUV - NUV color if the sample is restricted to galaxies below z < 0.1. Taking advantage of the UV and IR data, we estimate the dust attenuation from the IR/UV ratio and compare it to the UV slope β. We find that it is not possible to uniquely estimate the dust attenuation from β for our sample of galaxies. These galaxies are highly extinguished with a median value AFUV = 2.7 ± 0.8. Once the dust correction is applied, the UV- and IR-based star formation rates correlate. For the closest galaxy with the best quality spectrum, we see a feature consistent with being produced by a bump near 220 nm in the attenuation curve.