The presence of massive black holes (BHs) with masses of the order of $10^9\, {\rm M_\odot }$, powering bright quasars when the Universe was less than 1 Gyr old, poses strong constraints on their formation mechanism. Several scenarios have been proposed to date to explain massive BH formation, from the low-mass seed BH remnants of the first generation of stars to the massive seed BHs resulting from the rapid collapse of massive gas clouds. However, the plausibility of some of these scenarios to occur within the progenitors of high-z quasars has not yet been thoroughly explored. In this work, we investigate, by combining dark-matter only N-body simulations with a semi-analytic framework, whether the conditions for the formation of massive seed BHs from synchronized atomic-cooling halo pairs and/or dynamically heated (DH) mini-haloes are fulfilled in the overdense regions where the progenitors of a typical high-redshift quasar host form and evolve. Our analysis shows that the peculiar conditions in such regions, i.e. strong halo clustering and high star formation rates, are crucial to produce a non-negligible number of massive seed BH host candidates: we find ≈1400 DH metal-free mini-haloes, including one of these which evolves to a synchronized pair and ends up in the massive quasar-host halo by z = 6. This demonstrates that the progenitors of high-redshift quasar host haloes can harbour early massive seed BHs. Our results further suggest that multiple massive seed BHs may form in or near the quasar host’s progenitors, potentially merging at lower redshifts and yielding gravitational wave events.

中文翻译：

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在高红移类星体宿主祖先中形成巨大的种子黑洞

当宇宙小于 1 Gyr 时，质量为 $10^9\, {\rm M_\odot }$ 的大质量黑洞 (BH) 的存在为明亮的类星体提供动力，这对其形成机制构成了强烈的限制。迄今为止，已经提出了几种方案来解释大质量 BH 的形成，从第一代恒星的低质量种子 BH 残余物到由大质量气体云快速塌缩产生的大质量种子 BH。然而，其中一些情景发生在高 z 类星体的祖先中的合理性尚未得到彻底探索。在这项工作中，我们通过将仅暗物质的 N 体模拟与半解析框架相结合来进行研究，在典型的高红移类星体宿主形成和演化的高密度区域，是否满足从同步原子冷却晕对和/或动态加热（DH）迷你晕形成大量种子 BH 的条件。我们的分析表明，这些区域的特殊条件，即强光晕聚集和高恒星形成率，对于产生不可忽略的大量种子 BH 宿主候选者至关重要：我们发现 ≈1400 DH 无金属迷你光晕，包括其中一个演化为同步对，并在 z = 6 时最终进入巨大的类星体宿主晕。这表明高红移类星体宿主晕的祖先可以拥有早期的大质量种子 BH。我们的研究结果进一步表明，在类星体宿主的祖细胞中或附近可能会形成多个巨大的种子 BH，