Calibrating UV Star Formation Rates for Dwarf Galaxies from STARBIRDS

TL;DR

This paper compares UV-based and resolved stellar population SFRs in dwarf galaxies, finds systematic deviations especially in FUV, and proposes an empirical calibration to improve SFR estimates from UV data.

Contribution

It introduces an empirical FUV-SFR calibration for dwarf galaxies, addressing discrepancies with previous models and improving SFR measurement accuracy.

Findings

Near UV fluxes from CMD-based SFRs agree with observations

Far UV fluxes show systematic deviations from models

New empirical FUV-SFR relation is ~53% larger than previous ones

Abstract

Integrating our knowledge of star formation traced by observations at different wavelengths is essential for correctly interpreting and comparing star formation activity in a variety of systems and environments. This study compares extinction corrected integrated ultraviolet (UV) emission from resolved galaxies with color-magnitude diagram (CMD) based star formation rates (SFRs) derived from resolved stellar populations and CMD fitting techniques in 19 nearby starburst and post-starburst dwarf galaxies. The datasets are from the panchromatic STARBurst IRregular Dwarf Survey (STARBIRDS) and include deep legacy GALEX UV imaging, HST optical imaging, and Spitzer MIPS imaging. For the majority of the sample, the integrated near UV fluxes predicted from the CMD-based SFRs - using four different models - agree with the measured, extinction corrected, integrated near UV fluxes from GALEX images, but the far UV predicted fluxes do not. Further, we find a systematic deviation between the SFRs based on integrated far UV luminosities and existing scaling relations, and the SFRs based on the resolved stellar populations. This offset is not driven by different star formation timescales, variations in SFRs, UV attenuation, nor stochastic effects. This first comparison between CMD-based SFRs and an integrated FUV emission SFR indicator suggests that the most likely cause of the discrepancy is the theoretical FUV-SFR calibration from stellar evolutionary libraries and/or stellar atmospheric models. We present an empirical calibration of the FUV-based SFR relation for dwarf galaxies, with uncertainties, which is ~53% larger than previous relations.