arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1908.11149astro-ph.GA
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星系HI的起源

Origin of the galaxy HI size-mass relation

Adam R. H. Stevens, Benedikt Diemer, Claudia del P. Lagos, Dylan Nelson, Danail Obreschkow, Jing Wang, Federico Marinacci

摘要:

我们解析推导出所观察到的星系的原子氢(HI)的大小质量关系,包括其散射的限制,基于简单的假设HI盘的结构。我们尝试三个通用的配置文件HI表面密度作为半径的函数。首先,我们断言,HI表面密度饱和在一个可变的阈值,否则下降与半径或,其次,半径平方指数。我们的第三个模型假设总气体表面密度是指数的,在每个半径处的HI分数取决于局部压力。这些测试对汇编的110个星系的东西,小东西,LVHIS,和蓝盘调查,其HI表面密度分布得到很好的解决。所有模型都很好地拟合了观测结果,并预测了一致的尺寸-质量关系。使用的分析参数,我们解释了为什么过程中,导致气体盘截断-如冲压压力剥离-几乎不影响HI的尺寸质量关系。这是用IllustrisTNG(100)宇宙学,流体动力学模拟和黑暗圣人半解析模型的星系形成,这两个捕获径向分辨盘结构进行测试。对于m_*>10^9 M_solar和m_HI>10^8 M_solar的星系,两个模拟都预测了HI的大小-质量关系,与观测结果一致,显示中心星系和卫星星系之间没有差异,并且仅显示卫星星系对宿主晕质量的次要二阶依赖性。最终,普遍紧密的HI尺寸-质量关系在数学上是不可避免的和稳健的。只有通过完全破坏HI盘的结构,例如通过过于强大的反馈,模拟才能很好地预测这种关系。

英文摘要:

We analytically derive the observed size-mass relation of galaxies' atomic hydrogen (HI), including limits on its scatter, based on simple assumptions about the structure of HI discs. We trial three generic profiles for HI surface density as a function of radius. Firstly, we assert that HI surface densities saturate at a variable threshold, and otherwise fall off exponentially with radius or, secondly, radius squared. Our third model assumes the total gas surface density is exponential, with the HI fraction at each radius depending on local pressure. These are tested against a compilation of 110 galaxies from the THINGS, LITTLE THINGS, LVHIS, and Bluedisk surveys, whose HI surface density profiles are well resolved. All models fit the observations well and predict consistent size-mass relations. Using an analytical argument, we explain why processes that cause gas disc truncation - such as ram-pressure stripping - scarcely affect the HI size-mass relation. This is tested with the IllustrisTNG(100) cosmological, hydrodynamic simulation and the Dark Sage semi-analytic model of galaxy formation, both of which capture radially resolved disc structure. For galaxies with m_*>10^9 M_solar and m_HI>10^8 M_solar, both simulations predict HI size-mass relations that align with observations, show no difference between central and satellite galaxies, and show only a minor, second-order dependence on host halo mass for satellites. Ultimately, the universally tight HI size-mass relation is mathematically inevitable and robust. Only by completely disrupting the structure of HI discs, e.g. through overly powerful feedback, could a simulation predict the relation poorly.

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