Ultraviolet–to–Far‐Infrared Properties of Local Star‐forming Galaxies

Abstract

We present the results of a multiwavelength study of nearby galaxies aimed at understanding the relation between the ultraviolet and far-infrared emission in star-forming galaxies. The data set comprises new ultraviolet (from HST STIS), ground-based Hα, and radio continuum observations, together with archival infrared data (from IRAS and ISO). The local galaxies are used as benchmarks for comparison of the infrared-to-ultraviolet properties with two populations of high-redshift galaxies: the submillimeter star-forming galaxies detected by SCUBA and the ultraviolet-selected Lyman break galaxies (LBGs). In addition, the long wavelength baseline covered by the present data enables us to compare the star formation rates (SFRs) derived from the observed ultraviolet, Hα, infrared, and radio luminosities and to gauge the impact of dust opacity in the local galaxies. We also derive a new calibration for the nonthermal part of the radio SFR estimator, based on the comparison of 1.4 GHz measurements with a new estimator of the bolometric luminosity of the star-forming regions. We find that more actively star-forming galaxies show higher dust opacities, which is in line with previous results. We find that the local star-forming galaxies have a lower Fλ(205 μm)/Fλ(UV) ratio by 2-3 orders of magnitude than the submillimeter-selected galaxies and may have a similar or somewhat higher Fλ(205 μm)/Fλ(UV) ratio than LBGs. The Fλ(205 μm)/Fλ(UV) ratio of the local galaxy population may be influenced by the cool dust emission in the far-infrared heated by nonionizing stellar populations, which may be reduced or absent in the LBGs.