The effects of local stellar radiation and dust depletion on non-equilibrium interstellar chemistry
The effects of local stellar radiation and dust depletion on non-equilibrium interstellar chemistry
复制标题
局部恒星辐射和尘埃损耗对非平衡星际化学的影响
DOI：
10.1093/mnras/stac2338
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发表时间：
2022
影响因子：
4.8
通讯作者：
Hayward, Christopher C.
中科院分区：
文献类型：
--
作者：
Richings, Alexander J.;Faucher-Giguère, Claude-André;Gurvich, Alexander B.;Schaye, Joop;Hayward, Christopher C.
星际化学对星系的形成很重要，因为它决定了气体冷却的速度，并使我们能够预测可观察到的离子和分子光谱线。我们探讨了星际介质（ISM）化学建模的两个核心方面：(1)局部恒星辐射的影响，它使气体电离并加热，(2)金属在尘埃颗粒上的耗竭，这减少了气相中金属的丰度。我们对孤立的盘状星系进行了高分辨率（每个重子粒子400 μ M⊙）的模拟，从矮星到银河系质量，使用了5个星系形成模型以及化学、非平衡化学和冷却模块。在我们的基础模型中，我们使用近似的辐射转移方案将化学与恒星粒子计算的恒星通量耦合起来；我们对金属耗竭实施了一个基于密度的经验处方。为了进行比较，我们还在空间均匀辐射场下进行了模拟，并且没有金属损耗。我们的基准模型大致再现了观测到的Hiand H2mass与恒星质量的趋势，以及[Cii]、[Oi]、[Oiii]、[Nii]和H α6563Å的光度与恒星形成率的关系。我们在均匀辐射场的模拟中预测了[Oiii]和H α6563Å的亮度较弱，最高可达一个数量级，而忽略金属耗尽会使碳和氧谱线的亮度增加约2倍。然而，星系的整体演化不受局部恒星通量或金属耗尽的强烈影响，除非在矮星系中，局部通量的包含导致较弱的流出，从而导致较高的气体分数。
Interstellar chemistry is important for galaxy formation, as it determines the rate at which gas can cool, and enables us to make predictions for observable spectroscopic lines from ions and molecules. We explore two central aspects of modelling the chemistry of the interstellar medium (ISM): (1) the effects of local stellar radiation, which ionizes and heats the gas, and (2) the depletion of metals on to dust grains, which reduces the abundance of metals in the gas phase. We run high-resolution (400 M⊙per baryonic particle) simulations of isolated disc galaxies, from dwarfs to Milky Way-mass, using thefiregalaxy formation models together with thechimesnon-equilibrium chemistry and cooling module. In our fiducial model, we couple the chemistry to the stellar fluxes calculated from star particles using an approximate radiative transfer scheme; and we implement an empirical density-dependent prescription for metal depletion. For comparison, we also run simulations with a spatially uniform radiation field, and without metal depletion. Our fiducial model broadly reproduces observed trends in Hiand H2mass with stellar mass, and in line luminosity versus star formation rate for [Cii], [Oi], [Oiii], [Nii], and H α6563Å. Our simulations with a uniform radiation field predict fainter luminosities, by up to an order of magnitude for [Oiii]and H α6563Å, while ignoring metal depletion increases the luminosity of carbon and oxygen lines by a factor ≈ 2. However, the overall evolution of the galaxy is not strongly affected by local stellar fluxes or metal depletion, except in dwarf galaxies where the inclusion of local fluxes leads to weaker outflows and hence higher gas fractions.