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

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)-beta 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 similar to 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-beta 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-beta relation at z greater than or similar to 4.