MODELING THE EFFECTS OF STAR FORMATION HISTORIES ON Hα AND ULTRAVIOLET FLUXES IN NEARBY DWARF GALAXIES
MODELING THE EFFECTS OF STAR FORMATION HISTORIES ON Hα AND ULTRAVIOLET FLUXES IN NEARBY DWARF GALAXIES
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DOI：
10.1088/0004-637x/744/1/44
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发表时间：
2011-09
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通讯作者：
D. Weisz;D. Weisz;Benjamin D. Johnson;L. Johnson;E. Skillman;Janice C. Lee;Janice C. Lee;R. Kennicutt;D. Calzetti;L. V. Zee;M. Bothwell;J. Dalcanton;D. Dale;B. Williams
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作者：
D. Weisz;D. Weisz;Benjamin D. Johnson;L. Johnson;E. Skillman;Janice C. Lee;Janice C. Lee;R. Kennicutt;D. Calzetti;L. V. Zee;M. Bothwell;J. Dalcanton;D. Dale;B. Williams
研究了非恒定星星形成历史对Hα和GALEX远紫外（FUV）星星形成率（SFR）指标的影响.在假设完全填充的Chabrier初始质量函数（IMF）的条件下，我们比较了来自1500个简单周期模型SFH的Hα-FUV通量比的分布与来自Spitzer Local Volume Legacy巡天的185个星系的观测结果。我们发现了一组与数据匹配良好的SFH模型，使得更大质量的星系最好以几乎恒定的SFH为特征，而低质量系统经历了1.30的爆发幅度（即，在爆发间隔期间，SFR比SFR增加了30倍），爆发持续时间为数十亿年，周期为2.5亿年;这些SFH与在具有较低SFR的系统中预期的随机星星形成的增加大致一致。我们分析了预测的星系恒星质量、R波段表面亮度、Hα导出的SFR和蓝色光度的时间演化，发现它们与观测到的通量分布有合理的匹配。我们发现，我们的模型SFH通常能够再现所观察到的系统性下降和增加的分散在Hα-到-FUV比向低质量系统，而不调用其他物理机制。我们还比较了我们的预测与那些从一个恒定的SFR的综合银河IMF理论。我们发现，虽然这两个预测的观测比率的系统性下降，只有时间变量SFH模型能够产生的低质量星系（M* 107 M的反馈）与正常的Hα-到-FUV比的观察人口。这些结果表明，一个变量IMF单独难以解释观察到的分散在Hα-到-FUV的比率。最后，我们考虑模型SFH的局限性，并讨论了使用额外的经验约束，以提高未来的SFH建模工作。
We consider the effects of non-constant star formation histories (SFHs) on Hα 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 Hα-to-FUV flux ratios from ∼1500 simple, periodic model SFHs with observations of 185 galaxies from the 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, Hα-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 Hα-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 (M* ≲ 107 M☉) with normal Hα-to-FUV ratios. These results demonstrate that a variable IMF alone has difficulty explaining the observed scatter in the Hα-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.