The Star Formation Reference Survey-V: the effect of extinction, stellar mass, metallicity, and nuclear activity on star-formation rates based on H$\alpha$ emission

TL;DR

This study calibrates and compares various star-formation rate indicators in local star-forming galaxies, analyzing effects of extinction, stellar mass, metallicity, and nuclear activity on Hα-based SFR measurements.

Contribution

It provides new calibrations for Hα, infrared, and radio-based SFRs, accounting for extinction and galaxy properties, enhancing accuracy of star-formation estimates.

Findings

Hα-based SFRs can be calibrated with IR and radio data.

Extinction corrections significantly impact SFR estimates.

Galaxy metallicity correlates with extinction levels.

Abstract

We present new H$\alpha$ photometry for the Star-Formation Reference Survey (SFRS), a representative sample of star-forming galaxies in the local Universe. Combining these data with the panchromatic coverage of the SFRS, we provide calibrations of H$\alpha$-based star-formation rates (SFRs) with and without correction for the contribution of [$\rm N_{^{II}}$] emission. We consider the effect of extinction corrections based on the Balmer decrement, infrared excess (IRX), and spectral energy distribution (SED) fits. We compare the SFR estimates derived from SED fits, polycyclic aromatic hydrocarbons, hybrid indicators such as 24 $\mu$m + H$\alpha$, 8 $\mu$m + H$\alpha$, FIR + FUV, and H$\alpha$ emission for a sample of purely star-forming galaxies. We provide a new calibration for 1.4 GHz-based SFRs by comparing to the H$\alpha$ emission, and we measure a dependence of the radio-to-H$\alpha$ emission ratio based on galaxy stellar mass. Active galactic nuclei introduce biases in the calibrations of different SFR indicators but have only a minimal effect on the inferred SFR densities from galaxy surveys. Finally, we quantify the correlation between galaxy metallicity and extinction.