Converting H$\alpha$ Luminosities into Star Formation Rates

TL;DR

This paper introduces a revised relation between H-alpha luminosity and star formation rate that accounts for the IGIMF's variable slope, suggesting previous estimates of SFRs are underestimated and impacting cosmological star formation history.

Contribution

It presents a new relation linking H-alpha luminosity to SFR that incorporates the IGIMF's dependence on SFR, improving accuracy over classical methods.

Findings

Classical SFR-H-alpha relation underestimates SFRs.

IGIMF slope varies with SFR, affecting luminosity calculations.

Revised relation may alter understanding of cosmic star formation history.

Abstract

The recent finding that the IGIMF (integrated galaxial initial stellar mass function) composed of all newly formed stars in all young star clusters has, in dependence of the SFR, a steeper slope in the high mass regime than the underlying canonical IMF of each star cluster offers new insights into the galactic star formation process: The classical linear relation between the SFR and the produced H$\alpha$ luminosity is broken and SFRs are always underestimated. Our new relation is likely to lead to a revision of the cosmological SFH.