AI 中文总结
该研究针对JWST观测到的早期超大质量黑洞与小红点的快速增长问题，提出冷模式吸积是必要条件，可自然解释二者的质量与数密度，完善了早期宇宙结构形成理论。
AI 中文摘要
詹姆斯·韦布空间望远镜（JWST）观测到，宇宙大爆炸后仅数亿年就形成了超大质量黑洞/活动星系核（SMBHs/AGN），这对理论理解提出了挑战：它们在初始种子形成后，如何如此快速地增长到超大质量（$M_{\rm BH} > 10^6 {\rm \thinspace M}_\u2609$）？这种快速增长是否与JWST发现的众多神秘小红点（LRDs，具有类AGN特征的致密源）有关？为解决这些谜团，我们考虑SMBH增长的一阶约束：必须有足够的重子物质到达位于宿主暗物质晕引力势阱底部的SMBH种子附近。我们专门研究冷模式吸积，即宇宙环境中的气体以冷流形式流入已位力化的晕，未被激波加热，能在自由下落时标内高效到达中心。我们发现，冷模式吸积是SMBH达到观测质量的必要条件，而对于被激波加热的气体流入，所需物质只能由极罕见的晕提供；此外，罕见（约1 Gpc$^{-3}$）晕中的冷模式流入匹配大质量类星体的质量与数量，能支持大质量SMBH（约$10^7$ M$_\u2609$）超爱丁顿吸积的晕则匹配LRD的数密度，低红移处LRD丰度的降低可能反映了生长中宿主晕内冷模式吸积的终止，因此早期大质量SMBH与LRD的群体可自然源于宇宙结构形成，基于能通过冷吸积提供足够物质的晕的丰度。
英文摘要
Supermassive black holes/active galactic nuclei (SMBHs/AGN), forming only a few hundred million years after the Big Bang as observed with the James Webb Space Telescope (JWST), challenge theoretical understanding. How could they grow so massive $(M_{\rm BH} > 10^6 {\rm \,M}_\odot)$ so quickly after initial seeding? Is this rapid growth related to the numerous and enigmatic Little Red Dots (LRDs), compact sources with AGN-like characteristics, discovered by JWST? To address these mysteries, we consider the first-order constraint on SMBH growth: enough baryonic material has to reach the vicinity of the SMBH seed, located near the bottom of the gravitational potential well of the host dark matter halo. We specifically examine cold-mode accretion, where gas from the cosmic environment flows into the virialized halo in cold streams without being shock-heated, efficiently reaching the center on a free-fall timescale. We find that cold mode accretion is necessary to supply material for the SMBHs to reach the observed masses, whereas for shock-heated gas inflow the required amount could only be supplied by implausibly rare halos. Moreover, cold-mode inflow in rare $(\sim1$ Gpc$^{-3}$) halos matches the mass and number of the massive quasars, and halos able to support super-Eddington accretion for massive SMBHs ($\sim10^7$ M$_\odot$) match LRD number densities. The decreasing LRD abundance at lower redshifts may then reflect the termination of cold-mode accretion in the growing host halos. The populations of massive SMBHs and LRDs at early times may thus arise naturally from cosmological structure formation, based on the abundance of halos capable of supplying sufficient material through cold accretion.
Comments10 pages, 5 figures, Submitted to the Open Journal of Astrophysics
