The existence of $\approx$10^9 Msun supermassive black holes (SMBHs) within the first billion year of the universe has stimulated numerous ideas for the prompt formation and rapid growth of BHs in the early universe. Here we review ways in which the seeds of massive BHs may have first assembled, how they may have subsequently grown as massive as $\approx$10^9 Msun, and how multi-messenger observations could distinguish between different SMBH assembly scenarios. We conclude the following: (1) The ultra-rare $\approx$10^9 Msun SMBHs represent only the tip of the iceberg. Early BHs likely fill a continuum from stellar-mass (approx. 10 Msun) to the super-massive ($\approx$10^9 Msun) regime, reflecting a range of initial masses and growth histories. (2) Stellar-mass BHs were likely left behind by the first generation of stars at redshifts as high as z=30, but their initial growth was typically stunted due to the shallow potential wells of their host galaxies. (3) Conditions in some larger, metal-poor galaxies soon became conducive to the rapid formation and growth of massive `seed' holes, via gas accretion and by mergers in dense stellar clusters. (4) BH masses depend on the environment (such as the number and properties of nearby radiation sources and the local baryonic streaming velocity), and on the metal enrichment and assembly history of the host galaxy. (5) Distinguishing between assembly mechanisms will be difficult, but a combination of observations by LISA (probing massive BH growth via mergers) and by deep multi-wavelength electromagnetic observations (probing growth via gas accretion) is particularly promising.

中文翻译：

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第一个大质量黑洞的集合

在宇宙诞生的第一个 10 亿年中，$\approx $10^9 Msun 超大质量黑洞 (SMBHs) 的存在激发了许多关于 BHs 在早期宇宙中迅速形成和快速增长的想法。在这里，我们回顾了大规模 BH 的种子可能首次组装的方式，它们随后如何增长到 $\approx $10^9 Msun，以及多信使观察如何区分不同的 SMBH 组装场景。我们得出以下结论： (1) 极其罕见的 $\approx$10^9 Msun SMBH 仅代表冰山一角。早期的 BH 可能会填充从恒星质量（约 10 Msun）到超大质量（$\约 $10^9 Msun）的连续体，反映了一系列初始质量和生长历史。(2) 恒星质量的 BHs 很可能是第一代恒星在 z=30 时留下的红移，但由于其宿主星系的势阱较浅，它们的初始生长通常受阻。(3) 通过气体吸积和密集星团的合并，一些较大的、缺乏金属的星系的条件很快就变得有利于大量“种子”洞的快速形成和增长。(4) BH 质量取决于环境（如附近辐射源的数量和性质以及当地的重子流速度），以及宿主星系的金属富集和组装历史。(5) 很难区分装配机构，