paper

The Bursty Star Formation Histories of Low-mass Galaxies at Revealed by Star Formation Rates Measured from H and FUV

arXiv:1604.05314 · doi:10.3847/1538-4357/833/1/37

Abstract

We investigate the burstiness of star formation histories (SFHs) of galaxies at by using the ratio of star formation rates (SFRs) measured from H and FUV (1500 Å) (H--to--FUV ratio). Our sample contains 164 galaxies down to stellar mass (M*) of in the CANDELS GOODS-N region, where Team Keck Redshift Survey DEIMOS spectroscopy and HST/WFC3 F275W images from CANDELS and Hubble Deep UV Legacy Survey are available. When the {\it ratio} of H- and FUV-derived SFRs is measured, dust extinction correction is negligible (except for very dusty galaxies) with the Calzetti attenuation curve. The H--to--FUV ratio of our sample increases with M* and SFR. The median ratio is 0.7 at M* (or SFR) and increases to 1 at M* (or SFR ). At M*, our median H--to--FUV ratio is lower than that of local galaxies at the same M*, implying a redshift evolution. Bursty SFH on a timescale of a few tens of megayears on galactic scales provides a plausible explanation of our results, and the importance of the burstiness increases as M* decreases. Due to sample selection effects, our H--to--FUV ratio may be an upper limit of the true value of a complete sample, which strengthens our conclusions. Other models, e.g., non-universal initial mass function or stochastic star formation on star cluster scales, are unable to plausibly explain our results.

13 pages, 8 figures. ApJ accepted. The main conclusions are not changed. Major modifications include: (1) to be consistent with the literature, now reporting Hβ--to--FUV ratio (rather than FUV--to--Hβ in the first version); (2) detailed discussions on dust extinction correction; (3) new SF bustiness calculation; and (4) enriched discussions in Introduction

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