GAMA/H-ATLAS: Common star-formation rate indicators and their dependence on galaxy physical parameters

TL;DR

This study compares various star-formation rate indicators in local galaxies, analyzing their dependence on galaxy properties and calibrating attenuation corrections to improve SFR estimates.

Contribution

It provides a calibration of UV-based SFRs using IR and Halpha data, highlighting the limitations of beta as an attenuation indicator and the dependence of corrections on galaxy parameters.

Findings

UV-based SFRs can be aligned with IR and Halpha indicators after calibration.

Beta alone is unreliable for dust attenuation correction.

Attenuation corrections depend on stellar mass, redshift, and dust temperature.

Abstract

We compare common star-formation rate (SFR) indicators in the local Universe in the GAMA equatorial fields (around 160 sq. deg.), using ultraviolet (UV) photometry from GALEX, far-infrared (FIR) and sub-millimetre (sub-mm) photometry from H-ATLAS, and Halpha spectroscopy from the GAMA survey. With a high-quality sample of 745 galaxies (median redshift 0.08), we consider three SFR tracers: UV luminosity corrected for dust attenuation using the UV spectral slope beta (SFRUV,corr), Halpha line luminosity corrected for dust using the Balmer decrement (BD) (SFRHalpha,corr), and the combination of UV and IR emission (SFRUV+IR). We demonstrate that SFRUV,corr can be reconciled with the other two tracers after applying attenuation corrections by calibrating IRX (i.e. the IR to UV luminosity ratio) and attenuation in the Halpha (derived from BD) against beta. However, beta on its own is very unlikely to be a reliable attenuation indicator. We find that attenuation correction factors depend on parameters such as stellar mass, z and dust temperature (Tdust), but not on Halpha equivalent width (EW) or Sersic index. Due to the large scatter in the IRX vs beta correlation, when compared to SFRUV+IR, the beta-corrected SFRUV,corr exhibits systematic deviations as a function of IRX, BD and Tdust.