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arXiv 2103.12124astro-ph.GA
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游荡黑洞的起源和人口统计

Origins and Demographics of Wandering Black Holes

Angelo Ricarte, Michael Tremmel, Priyamvada Natarajan, Charlotte Zimmer, Thomas Quinn

摘要:

在罗慕路斯宇宙学模拟中,我们将游荡的黑洞定义为那些物理上偏离其晕中心的黑洞。与目前大多数其他可用的宇宙学模拟不同,黑洞是基于局部气体性质的种子,并允许动态演化而不固定在晕中心。跟踪这些黑洞使我们能够对偏移人口做出可靠的预测。我们发现游荡黑洞的数量与晕的质量大致成线性关系,因此我们预计在星系团晕中有数千个游荡黑洞。在当地,这些流浪者占当地黑洞质量预算的10%左右,一旦种子质量被占。然而,对于更高的红移($z\gtrsim 4$),游荡的黑洞都超过和超越了它们中心的超大质量黑洞。我们发现,大多数游荡的黑洞仍然靠近种子质量,并且起源于先前被破坏的卫星星系的中心。虽然大多数没有保留一个解析的恒星对应物,但那些保留的恒星位于更远的维里半径的更大部分。具有较高光度的流浪者更倾向于在较低的半径,更大的质量,或者更接近其宿主的中平面,或者与恒星过密度有关。这个分析表明,我们目前对超大质量黑洞的普查是不完整的,而且可能存在大量的偏离中心的流浪者。

英文摘要:

We characterise the population of wandering black holes, defined as those physically offset from their halo centres, in the Romulus cosmological simulations. Unlike most other currently available cosmological simulations, black holes are seeded based on local gas properties and are permitted to evolve dynamically without being fixed at halo centres. Tracking these black holes allows us to make robust predictions about the offset population. We find that the number of wandering black holes scales roughly linearly with the halo mass, such that we expect thousands of wandering black holes in galaxy cluster halos. Locally, these wanderers account for around 10 per cent of the local black hole mass budget once seed masses are accounted for. Yet for higher redshifts ($z\gtrsim 4$), wandering black holes both outweigh and outshine their central supermassive counterparts. Most wandering black holes, we find, remain close to the seed mass and originate from the centres of previously disrupted satellite galaxies. While most do not retain a resolved stellar counterpart, those that do are situated farther out at larger fractions of the virial radius. Wanderers with higher luminosities are preferentially at lower radius, more massive, and either closer to their host's mid-planes or associated with a stellar overdensity. This analysis shows that our current census of supermassive black holes is incomplete and that a substantial population of off-centre wanderers likely exists.

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