A direct calibration of the IRX-{\beta} relation in Lyman-break Galaxies at z=3-5

TL;DR

This study investigates the IRX-{eta} relation in high-redshift Lyman-break galaxies, confirming its consistency with a Calzetti-like law up to z~5 and highlighting the importance of stellar mass in dust correction.

Contribution

It provides a direct calibration of the IRX-{eta} relation at z=3-5 using stacking analysis, and emphasizes the role of stellar mass in dust correction methods.

Findings

No significant evolution of IRX-{eta} relation up to z~5

IRX-{eta} relation is consistent with a Calzetti-like attenuation law

IRX-stellar mass relation is a better proxy for dust correction

Abstract

We use a sample of 4178 Lyman break galaxies (LBGs) at z = 3, 4 and 5 in the UKIRT Infrared Deep Sky Survey (UKIDSS) Ultra Deep Survey (UDS) field to investigate the relationship between the observed slope of the stellar continuum emission in the ultraviolet, {\beta}, and the thermal dust emission, as quantified via the so-called 'infrared excess' (IRX = LIR/LUV). Through a stacking analysis we directly measure the 850-{\mu}m flux density of LBGs in our deep (0.9mJy) James Clerk Maxwell Telescope (JCMT) SCUBA-2 850-{\mu}m map, as well as deep public Herschel/SPIRE 250-, 350- and 500-{\mu}m imaging. We establish functional forms for the IRX-{\beta} relation to z ~ 5, confirming that there is no significant redshift evolution of the relation and that the resulting average IRX-{\beta} curve is consistent with a Calzetti-like attenuation law. We compare our results with recent work in the literature, finding that discrepancies in the slope of the IRX-{\beta} relation are driven by biases in the methodology used to determine the ultraviolet slopes. Consistent results are found when IRX-{\beta} is evaluated by stacking in bins of stellar mass, M, and we argue that the near-linear IRX-M relationship is a better proxy for correcting observed UV luminosities to total star formation rates, provided an accurate handle on M can be had, and also gives clues as to the physical driver of the role of dust-obscured star formation in high-redshift galaxies.