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首页> 外文OA文献 >Effects of Star Formation Stochasticity on the Ly-alpha & Lyman Continuum Emission from Dwarf Galaxies during Reionization
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Effects of Star Formation Stochasticity on the Ly-alpha & Lyman Continuum Emission from Dwarf Galaxies during Reionization

机译：恒星形成随机性对Ly-alpha和Lyman的影响   再生过程中矮星系的连续发射

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Observations of distant galaxies play a key role in improving ourunderstanding of the Epoch of Reionization (EoR). The observed Ly-alphaemission line strength - quantified by its restframe equivalent width (EW) -provides a valuable diagnostic of stellar populations and dust in galaxiesduring and after the EoR. In this paper we quantify the effects of starformation stochasticity on the predicted Ly-alpha EW in dwarf galaxies, usingthe publicly available code SLUG ('Stochastically Light Up Galaxies'). Wecompute the number of hydrogen ionizing photons, as well as flux in the Far UVfor a set of models with star formation rates (SFR) in the range 10-3-1Msol/yr. From these fluxes we compute the luminosity, L-alpha, and the EW ofthe Ly-alpha line. We find that stochasticity alone induces a broaddistribution in L-alpha and EW at a fixed SFR, and that the widths of thesedistributions decrease with increasing SFR. We parameterize the EW probabilitydensity function (PDF) as an SFR-dependent double power law. We find that it ispossible to have EW as low as ~EW0/4 and as high as ~3 times the EW0, where EW0denotes the expected EW in the absence of stochasticity. We argue thatstochasticity may therefore be important when linking drop-out and narrow-bandselected galaxies, when identifying population III galaxies, and that it mayhelp to explain the large EW (EW > 100 - 200 A) observed for a fraction ofLy-alpha- selected galaxies. Finally, we show that stochasticity can alsoaffect the inferred escape fraction of ionizing photons from galaxies. Inparticular, we argue that stochasticity may simultaneously explain the observedanomalous ratios of the Lyman continuum flux density to the (non-ionizing) UVcontinuum density in so-called Lyman-Bump galaxies at z = 3.1, as well as theabsence of such objects among a sample of z = 1.3 drop-out galaxies.
机译：遥远星系的观测在改善我们对电离时代（EoR）的理解中起着关键作用。观察到的Ly-α发射谱线强度-通过其剩余框架等效宽度（EW）进行定量-为星系中和EoR之后和之后的恒星种群和尘埃提供有价值的诊断。在本文中，我们使用公开可用的代码SLUG（“随机点亮星系”），量化了星型随机性对矮星系中预测的Ly-alpha EW的影响。对于一组恒星形成率（SFR）在10-3-1Msol / yr范围内的模型，我们计算了氢离子化光子的数量以及远紫外线中的通量。从这些通量中，我们计算出亮度，L-alpha和Ly-alpha线的EW。我们发现，随机性会在固定的SFR时引起L-alpha和EW的广泛分布，并且随着SFR的增加，这些分布的宽度会减小。我们将EW概率密度函数（PDF）参数化为依赖SFR的双幂定律。我们发现有可能使EW低至〜EW0 / 4并高达EW0的〜3倍，其中EW0表示在没有随机性的情况下的预期EW。我们认为，随机性因此在将辍学星系和窄带选择星系联系在一起时，在识别种群III星系时可能很重要，并且这可能有助于解释观察到的大电子战（EW> 100-200 A）所观察到的部分Ly-alpha-选星星系。最后，我们证明了随机性也会影响从银河系推断出的电离光子的逃逸率。特别是，我们认为随机性可能同时解释了在所谓的Lyman-Bump星系中z = 3.1时，Lyman连续谱通量密度与（非电离）UVcontinuum密度的观察到的异常比率，以及样本中此类物体的缺失的z = 1.3脱落星系。

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