Evolution of dust attenuation in star-forming galaxies with UV slope, stellar mass, and redshift out to z∼ 5

To set reliable constraints on the dust-obscured portion of star formation across cosmic time, an accurate calibration of the so-called infrared excess (̊m IRX ≡ L_ IR /L_ UV) and its dependence on intrinsic galaxy properties is required. While the local IRX-β relation (where F_łambda∝ łambda^β) has been widely used to correct for the effects of dust absorption and scattering, many recent high-redshift works show significant inconsistencies. They are most likely caused by differences in the assumed attenuation curves, dust temperatures, and galactic star-to-dust relative morphologies. We found a dependence of the IRX on the UV slope β, stellar mass M_*, and redshift out to z ≃ 5. We also established consistent functional relations that can be used for correcting the UV/optical-selected galaxy samples for the effects of dust absorption. This work is based on a K-band selected sample of ∼ 10⁵ star-forming galaxies detected in the UDS and COSMOS fields. Quiescent sources and known starbursts have been removed, while the IR luminosities were established via stacking in FIR Herschel and JCMT maps. The UV slopes were determined from the spectral energy distribution (SED) fits and stacked IRX values were derived by taking the median of individual IRX measurements in bins of β, M_*, and redshift. While our best-fit IRX-β relation is consistent with a Calzetti-like attenuation curve at β≳ -1, at bluer values, the IRX appears to increase with redshift due to different mass-completeness limits imposed. When deriving the IRX-β relation in stellar-mass bins, a systematic trend was found, where the effective slope of the attenuation law becomes progressively shallower with increasing mass. We incorporated this into the IRX-β relation through the slope of the underlying reddening law, dA_ 1600 /dβ, which is a quadratic function of łog (M_*/ ̊m M_⊙). Expressing IRX as a function of the stellar mass, we find a tight correlation, with IRX rising monotonically with mass, while exhibiting a clear high-mass turnover at złesssim 2-3, consistent with suppressed cold-gas accretion and dust growth in massive systems.