H α emission in local galaxies: star formation, time variability, and the diffuse ionized gas
H α emission in local galaxies: star formation, time variability, and the diffuse ionized gas
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局域星系中的 H α 发射：恒星形成、时间变化和扩散电离气体
DOI：
10.1093/mnras/stac818
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发表时间：
2022
影响因子：
4.8
通讯作者：
Li, Hui
中科院分区：
文献类型：
--
作者：
Tacchella, Sandro;Smith, Aaron;Kannan, Rahul;Marinacci, Federico;Hernquist, Lars;Vogelsberger, Mark;Torrey, Paul;Sales, Laura;Li, Hui
星云复合线H α在局部和高红移宇宙中被广泛用作恒星形成速率（SFR）指标。我们提出了一项详细的高分辨率孤立银河系和大麦哲伦云模拟的H α辐射转移研究，包括辐射转移，非平衡热化学和尘埃演化。我们重点研究了H α发射的空间形态和时间变化，以及它与潜在气体和恒星形成特性的联系。H α和H β的径向和垂直表面亮度分布与附近星系的观测结果非常吻合。我们发现来自碰撞激发的H α发射的分数为1 ~ 5 -，仅与半径和垂直高度有微弱的依赖关系，散射使H α的光度增加了1 ~ 5。通过Balmer衰减进行的粉尘校正效果很好（本征H α发射在25%内可恢复），尽管粉尘衰减规律取决于空间分辨尺度和综合尺度上的衰减量本身。对理解H α-SFR连接很重要的是尘埃和氦对电离辐射（Lyman continuum [LyC]光子）的吸收，它们分别约为和。加上逃逸分数，这将使氢线排放的可用预算减少近一半（）。我们讨论了漫射电离气体的影响，其中显示了平面外的H α发射是由逃离圆盘的LyC光子驱动的。未来，这一框架在宇宙学（放大）模拟中的应用将有助于詹姆斯·韦伯太空望远镜对高红移星系的光谱分析。
The nebular recombination line H α is widely used as a star formation rate (SFR) indicator in the local and high-redshift Universe. We present a detailed H α radiative transfer study of high-resolution isolated Milky-Way and Large Magellanic Cloud simulations that include radiative transfer, non-equilibrium thermochemistry, and dust evolution. We focus on the spatial morphology and temporal variability of the H α emission, and its connection to the underlying gas and star formation properties. The H α and H β radial and vertical surface brightness profiles are in excellent agreement with observations of nearby galaxies. We find that the fraction of H α emission from collisional excitation amounts tofcol∼ 5–, only weakly dependent on radius and vertical height, and that scattering boosts the H α luminosity by. The dust correction via the Balmer decrement works well (intrinsic H α emission recoverable within 25 per cent), though the dust attenuation law depends on the amount of attenuation itself both on spatially resolved and integrated scales. Important for the understanding of the H α–SFR connection is the dust and helium absorption of ionizing radiation (Lyman continuum [LyC] photons), which are aboutand, respectively. Together with an escape fraction of, this reduces the available budget for hydrogen line emission by nearly half (). We discuss the impact of the diffuse ionized gas, showing – among other things – that the extraplanar H α emission is powered by LyC photons escaping the disc. Future applications of this framework to cosmological (zoom-in) simulations will assist in the interpretation of spectroscopy of high-redshift galaxies with the upcomingJames Webb Space Telescope.