Dark-age reionization and galaxy formation simulation - XIX. Predictions of infrared excess and cosmic star formation rate density from UV observations

Abstract

We present a new analysis of high-redshift UV observations using a semi-analytic galaxy formation model, and provide self-consistent predictions of the infrared excess (IRX)–β relations and cosmic star formation rate density. We combine the Charlot & Fall dust attenuation model with the MERAXES semi-analytic model, and explore three different parametrizations for the dust optical depths, linked to star formation rate, dust-to-gas ratio, and gas column density, respectively. A Bayesian approach is employed to statistically calibrate model-free parameters including star formation efficiency, mass loading factor, dust optical depths, and reddening slope directly against UV luminosity functions and colour–magnitude relations at z ∼ 4–7. The best-fitting models show excellent agreement with the observations. We calculate IRX using energy balance arguments and find that the large intrinsic scatter in the IRX–β plane correlates with specific star formation rate. Additionally, the difference among the three dust models suggests at least a factor of 2 systematic uncertainty in the dust-corrected star formation rate when using the Meurer IRX–β relation at z ≳ 4.