Dark matter-deficient dwarf galaxies form via tidal stripping of dark matter in interactions with massive companions
Dark matter-deficient dwarf galaxies form via tidal stripping of dark matter in interactions with massive companions
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DOI：
10.1093/mnras/stab093
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发表时间：
2021-02-05
影响因子：
4.8
通讯作者：
Peirani, S.
中科院分区：
文献类型：
--
作者：
Jackson, R. A.;Kaviraj, S.;Peirani, S.
在标准的Lambda CDM（Lambda冷暗物质）范式中，矮星系被认为是富含暗物质的，因为重子反馈被认为可以快速地将气体从它们的浅势威尔斯中驱逐出来，并在早期熄灭星星的形成。最近对暗物质含量极低的局部矮星的观测似乎与这一观点相矛盾，这可能会使标准模型的有效性受到质疑。我们使用NewHorizon，一个高分辨率的宇宙学模拟，来证明在大质量星系和矮卫星之间的潮汐相互作用中，暗物质的持续剥离，自然会产生暗物质缺乏的矮星，即使它们最初的暗物质分数是正常的。暗物质剥离的过程是负责大的散射晕恒星质量关系在矮制度。剥离的程度取决于矮星围绕其大质量伴星的轨道的接近程度，在极端情况下，产生的矮星的光环与恒星质量比低至1，这与最近的观测研究结果一致。类似于30%的矮星由于暗物质剥离而显示出与正常暗物质部分的一些偏差，其中10%显示出高水平的暗物质缺乏（M-晕/M-星< 10）。由于它们的轨道很近，很大一部分缺乏暗物质的矮星与它们的大质量同伴合并（例如，在类似3.5 Gyr的时间尺度上，大约有70%的合并），缺乏暗物质的矮星群不断地被矮星和大质量同伴之间的新相互作用所补充。因此，这些星系的产生是星系演化的自然副产品，它们的存在与标准范式并不矛盾。
In the standard Lambda CDM (Lambda cold dark matter) paradigm, dwarf galaxies are expected to be dark matter-rich, as baryonic feedback is thought to quickly drive gas out of their shallow potential wells and quench star formation at early epochs. Recent observations of local dwarfs with extremely low dark matter content appear to contradict this picture, potentially bringing the validity of the standard model into question. We use NewHorizon, a high-resolution cosmological simulation, to demonstrate that sustained stripping of dark matter, in tidal interactions between a massive galaxy and a dwarf satellite, naturally produces dwarfs that are dark matter-deficient, even though their initial dark matter fractions are normal. The process of dark matter stripping is responsible for the large scatter in the halo-to-stellar mass relation in the dwarf regime. The degree of stripping is driven by the closeness of the orbit of the dwarf around its massive companion and, in extreme cases, produces dwarfs with halo-to-stellar mass ratios as low as unity, consistent with the findings of recent observational studies. similar to 30 percent of dwarfs show some deviation from normal dark matter fractions due to dark matter stripping, with 10 percent showing high levels of dark matter deficiency (M-halo/M-star < 10). Given their close orbits, a significant fraction of dark matter-deficient dwarfs merge with their massive companions (e.g. similar to 70 percent merge over time-scales of similar to 3.5 Gyr), with the dark matter-deficient population being constantly replenished by new interactions between dwarfs and massive companions. The creation of these galaxies is therefore a natural by-product of galaxy evolution and their existence is not in tension with the standard paradigm.