Mass Deficits, Stalling Radii, and the Merger Histories of Elliptical Galaxies
Mass Deficits, Stalling Radii, and the Merger Histories of Elliptical Galaxies
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DOI：
10.1086/506139
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发表时间：
2006-03
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影响因子：
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通讯作者：
D. Merritt
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文献类型：
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作者：
D. Merritt
双星超大质量黑洞以“质量赤字”的形式在星系核上留下印记，即由于双星喷射恒星而导致星系核质量减少。质量赤字的大小原则上与星系的合并历史有关，但这种关系从未被量化。这里使用高精度 N 体模拟来校准这种关系。质量赤字显示为 Mdef ≈ 0.5M12，其中 M12 是双星的总质量；人们发现这种关系中的系数仅微弱地依赖于 M2/M1 或星系预先存在的核密度分布。因此，在 𝒩 合并之后，Mdef ≈ 0.5𝒩M•，其中 M• 是最终（当前）黑洞质量。与观察到的质量赤字相比，该结果意味着 1 ≲ 𝒩 ≲ 3，符合分层结构形成模型。讨论了双星失速半径、超高速恒星的起源以及星系中心暗物质的分布的影响。
A binary supermassive black hole leaves an imprint on a galactic nucleus in the form of a "mass deficit," a decrease in the mass of the nucleus due to ejection of stars by the binary. The magnitude of the mass deficit is in principle related to the galaxy's merger history, but the relation has never been quantified. Here high-accuracy N-body simulations are used to calibrate this relation. Mass deficits are shown to be Mdef ≈ 0.5M12, with M12 the total mass of the binary; the coefficient in this relation is found to depend only weakly on M2/M1 or on the galaxy's preexisting nuclear density profile. Hence, after 𝒩 mergers, Mdef ≈ 0.5𝒩M•, with M• the final (current) black hole mass. When compared with observed mass deficits, this result implies 1 ≲ 𝒩 ≲ 3, in accord with hierarchical structure formation models. Implications for binary stalling radii, the origin of hypervelocity stars, and the distribution of dark matter at the centers of galaxies are discussed.