Measures of star formation rates from Infrared (Herschel) and UV (GALEX) emissions of galaxies in the HerMES fields

TL;DR

This study evaluates the effectiveness of IR and UV emissions as indicators of star formation rates in galaxies, using Herschel and GALEX data, revealing discrepancies with local galaxy relations and proposing revised attenuation estimates.

Contribution

It provides a comprehensive analysis of IR and UV diagnostics for star formation, highlighting differences from local galaxy relations and refining dust attenuation estimates.

Findings

IR and UV emissions correlate with star formation rates.

Dust attenuation in distant galaxies is lower than in local counterparts.

Common local starburst recipes overestimate dust correction in these galaxies.

Abstract

The reliability of infrared (IR) and ultraviolet (UV) emissions to measure star formation rates in galaxies is investigated for a large sample of galaxies observed with the SPIRE and PACS instruments on Herschel as part of the HerMES project. We build flux-limited 250 micron samples of sources at redshift z<1, cross-matched with the Spitzer/MIPS and GALEX catalogues. About 60 % of the Herschel sources are detected in UV. The total IR luminosities, L_IR, of the sources are estimated using a SED-fitting code that fits to fluxes between 24 and 500 micron. Dust attenuation is discussed on the basis of commonly-used diagnostics: the L_IR/L_UV ratio and the slope, beta, of the UV continuum. A mean dust attenuation A_UV of ~ 3 mag is measured in the samples. L_IR/L_UV is found to correlate with L_IR. Galaxies with L_IR > 10 ^{11} L_sun and 0.5< z<1 exhibit a mean dust attenuation A_UV about 0.7 mag lower than that found for their local counterparts, although with a large dispersion. Our galaxy samples span a large range of beta and L_IR/L_UV values which, for the most part, are distributed between the ranges defined by the relations found locally for starburst and normal star-forming galaxies. As a consequence the recipe commonly applied to local starbursts is found to overestimate the dust attenuation correction in our galaxy sample by a factor ~2-3 .