Quantifying Scatter in Galaxy Formation at the Lowest Masses
Quantifying Scatter in Galaxy Formation at the Lowest Masses
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DOI：
10.3847/1538-4357/ac0db6
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发表时间：
2021-01
期刊：
影响因子：
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通讯作者：
F. Munshi;A. Brooks;Elaad Applebaum;C. Christensen;T. Quinn;Serena K Sligh
中科院分区：
文献类型：
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作者：
F. Munshi;A. Brooks;Elaad Applebaum;C. Christensen;T. Quinn;Serena K Sligh
我们预测了矮小星系的恒星质量-晕质量关系，模拟星系的晕质量峰值为M峰=1011M⊙，向下进入超暗矮星范围至M峰=107M⊙。我们模拟的矮星质量为M星=790M⊙到8.2×108M⊙，对应的V带星等数从−2到−18.5。对于M峰和GT；1010M⊙，模拟的SMHM关系与文献测定的结果一致，包括显示0.3Dex的小散射。然而，对于低质量晕，SMHM关系中的散射度增加。我们首先给出了包含模拟恒星群的分辨率良好的光晕的结果，但我们认识到，光晕是否拥有星系本身就取决于质量分辨率。因此，我们采用概率模型来填充低于分辨率极限的“暗”晕，以预测SMHM关系的“本征”斜率和散射。我们拟合了恒星质量中线性增长的对数正态散射，在M峰=108M⊙处，它增长到大于1Dx。在我们的模拟探索的SMHM关系的最微弱的一端，一个星系不能仅仅根据它的光度来分配一个独特的晕质量。相反，我们根据我们的结果提供了一个随机填充低质量晕的公式。最后，我们表明，我们不断增长的对数正态散射使预测的恒星质量函数的暗端斜率变陡。
We predict the stellar mass–halo mass (SMHM) relationship for dwarf galaxies, using simulated galaxies with peak halo masses of M peak = 1011 M ⊙ down into the ultra-faint dwarf range to M peak = 107 M ⊙. Our simulated dwarfs have stellar masses of M star = 790 M ⊙ to 8.2 × 108 M ⊙, with corresponding V-band magnitudes from −2 to −18.5. For M peak > 1010 M ⊙, the simulated SMHM relationship agrees with literature determinations, including exhibiting a small scatter of 0.3 dex. However, the scatter in the SMHM relation increases for lower-mass halos. We first present results for well-resolved halos that contain a simulated stellar population, but recognize that whether a halo hosts a galaxy is inherently mass resolution dependent. We thus adopt a probabilistic model to populate “dark” halos below our resolution limit to predict an “intrinsic” slope and scatter for the SMHM relation. We fit linearly growing log-normal scatter in stellar mass, which grows to more than 1 dex at M peak = 108 M ⊙. At the faintest end of the SMHM relation probed by our simulations, a galaxy cannot be assigned a unique halo mass based solely on its luminosity. Instead, we provide a formula to stochastically populate low-mass halos following our results. Finally, we show that our growing log-normal scatter steepens the faint-end slope of the predicted stellar mass function.