A direct calibration of thtae IRX-β relation in Lyman-break Galaxies at z=3-5

We use a sample of 4209 Lyman-break galaxies (LBGs) at z similar or equal to 3, 4, and 5 in the UKIRT Infrared Deep Sky Survey Ultra Deep Survey 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 equivalent to L-IR/L-UV). Through a stacking analysis, we directly measure the 850-mu m flux density of LBGs in our deep (0.9 mJy) James Clerk Maxwell Telescope 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 similar to 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. Comparing our results with recent works in the literature, we confirm 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, and we argue that the near-linear IRX-M-star relationship is a better proxy for correcting observed ultraviolet luminosities to total star formation rates, provided an accurate handle on M-star and also gives clues as to the physical driver of the role of dust-obscured star formation in high-redshift galaxies.