剩余质量对星系质量估算的影响
The Effect of the Remnant Mass in Estimating Stellar Mass of Galaxies
摘要：
从光谱能量分布估计的银河系恒星质量的定义在文献中是模糊的;恒星质量是否包括恒星残骸的质量，即白矮星，中子星和黑洞，没有很好的描述。简单恒星星族的剩余质量在总质量（活质量+剩余质量）中所占的比例随恒星年龄的增加而单调增加，初始质量函数和金属丰度影响其增加率。由于星系是由许多恒星星族组成的，因此星系的残余质量分数可能以复杂的方式依赖于星系的总恒星质量。因此，星系的恒星质量函数的形状可能会改变，这取决于恒星质量的定义。为了探索这个问题，我们运行了宇宙流体动力学模拟，然后，我们发现，残余质量分数确实与星系的总恒星质量相关。然而，这种关联是弱的，残余分数可以被视为一个常数，它只取决于红移。因此，恒星质量函数的形状几乎不变，但它只是水平移动，如果残余质量包括或不包括。红移越低，位移越大，对于Chabrier IMF，在z=0时达到0.2-dex。由于这会引起系统的差异，我们在比较自己的结果时，应该注意“恒星”质量的定义。
英文摘要：
The definition of the galactic stellar mass estimated from the spectral energy distribution is ambiguous in the literature; whether the stellar mass includes the mass of the stellar remnants, i.e. white dwarfs, neutron stars, and black holes, is not well described. The remnant mass fraction in the total (living+remnant) stellar mass of a simple stellar population monotonically increases with the age of the population, and the initial mass function and metallicity affect the increasing rate. Since galaxies are composed of a number of stellar populations, the remnant mass fraction may depend on the total stellar mass of galaxies in a complex way. As a result, the shape of the stellar mass function of galaxies may change, depending on the definition of the stellar mass. In order to explore this issue, we ran a cosmological hydrodynamical simulation, and then, we have found that the remnant mass fraction indeed correlates with the total stellar mass of galaxies. However, this correlation is weak and the remnant fraction can be regarded as a constant which depends only on the redshift. Therefore, the shape of the stellar mass function is almost unchanged, but it simply shifts horizontally if the remnant mass includes or not. The shift is larger at lower redshift and it reaches 0.2-dex at z=0 for a Chabrier IMF. Since this causes a systematic difference, we should take care of the definition of the `stellar' mass, when comparing one's result with others.
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