Show simple item record Weisz, D.R. en Johnson, B.D. en Johnson, L.C. en Skillman, E.D. en Lee, J.C. en Kennicutt, R.C. en Calzetti, D. en Van Zee, L. en Bothwell, M.S. en Dalcanton, J.J. en Dale, D.A. en Williams, B.F. en 2014-11-03T18:04:17Z en 2014-11-03T18:04:17Z en 2012 en
dc.identifier.citation Weisz, D. R., Johnson, B. D., Johnson, L. C., Skillman, E. D., Lee, J. C., Kennicutt, R. C., . . . Williams, B. F. (2012). Modeling the effects of star formation histories on H$\alpha$ and ultraviolet fluxes in nearby dwarf galaxies. Astrophysical Journal, 744(1), 44. en
dc.description.abstract We consider the effects of non-constant star formation histories (SFHs) on $\text{H}\alpha$ and GALEX far-ultraviolet (FUV) star formation rate (SFR) indicators. Under the assumption of a fully populated Chabrier initial mass function (IMF), we compare the distribution of $\text{H}\alpha$-to-FUV flux ratios from ~1500 simple, periodic model SFHs with observations of 185 galaxies from the $\textit{Spitzer}$ Local Volume Legacy survey. We find a set of SFH models that are well matched to the data, such that more massive galaxies are best characterized by nearly constant SFHs, while low-mass systems experience burst amplitudes of ~30 (i.e., an increase in the SFR by a factor of 30 over the SFR during the inter-burst period), burst durations of tens of Myr, and periods of ~250 Myr; these SFHs are broadly consistent with the increased stochastic star formation expected in systems with lower SFRs. We analyze the predicted temporal evolution of galaxy stellar mass, R-band surface brightness, $\text{H}\alpha$-derived SFR, and blue luminosity, and find that they provide a reasonable match to observed flux distributions. We find that our model SFHs are generally able to reproduce both the observed systematic decline and increased scatter in $\text{H}\alpha$-to-FUV ratios toward low-mass systems, without invoking other physical mechanisms. We also compare our predictions with those from the Integrated Galactic IMF theory with a constant SFR. We find that while both predict a systematic decline in the observed ratios, only the time variable SFH models are capable of producing the observed population of low-mass galaxies $\big(M_{*} \lesssim 10^{7} M_{\odot}\big)$ with normal $\text{H}\alpha$-to-FUV ratios. These results demonstrate that a variable IMF alone has difficulty explaining the observed scatter in the $\text{H}\alpha$-to-FUV ratios. We conclude by considering the limitations of the model SFHs and discuss the use of additional empirical constraints to improve future SFH modeling efforts. en
dc.language.iso en_US en
dc.publisher The American Astronomical Society en
dc.relation.isversionof en
dc.rights © 2012 The American Astronomical Society en
dc.subject galaxies: dwarf en
dc.subject galaxies: evolution en
dc.subject galaxies: formation en
dc.subject galaxies: star formation en
dc.title Modeling the effects of star formation histories on H$\alpha$ and ultraviolet fluxes in nearby dwarf galaxies en
dc.type Article en
dc.altmetrics.display true en

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