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arXiv 1107.1253astro-ph.CO
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冷流和第一类类星体

Cold flows and the first quasars

Tiziana Di Matteo, Nishikanta Khandai, Colin DeGraf, Yu Feng, Rupert Croft, Julio Lopez, Volker Springel

摘要:

对最遥远的明亮类星体的观测表明,在最初的8亿年内,必须聚集10亿个太阳质量的超大质量黑洞。在我们的标准星系形成的情况下,这种快速增长意味着大的气体密度提供了持续的吸积在临界或超临界速率到一个初始的黑洞种子。在早期星系的中心,是否以及如何能够达到和维持如此高的黑洞吸积率,一直是一个长期存在的问题。在这里,我们使用我们新的宇宙流体动力学模拟(MassiveBlack)覆盖体积(0.75 \Gpc)^[3]适用于研究稀有的第一类类星体,以表明稳定的高密度冷气体流负责聚集第一类星系,产生高气体密度,导致持续的临界吸积率,因此快速增长与早在z~ 1时就存在的~10^9个太阳质量的黑洞相当。7.我们发现,在这些条件下,类星体的反馈是不能有效地阻止冷气体穿透中心区域,因此不能淬火吸积,直到主机星系达到M_halo > 10^{12}太阳质量。这种冷流驱动的类星体形成方案意味着它们应该在早期宇宙的星系中无处不在,并且主要的(原)星系合并并不是有效燃料供应和增长的必要条件,特别是对于最早的SMBH。

英文摘要:

Observations of the most distant bright quasars imply that billion solar mass supermassive black holes (SMBH) have to be assembled within the first eight hundred million years. Under our standard galaxy formation scenario such fast growth implies large gas densities providing sustained accretion at critical or supercritical rates onto an initial black hole seed. It has been a long standing question whether and how such high black hole accretion rates can be achieved and sustained at the centers of early galaxies. Here we use our new cosmological hydrodynamic simulation (MassiveBlack) covering a volume (0.75 \Gpc)^3 appropriate for studying the rare first quasars to show that steady high density cold gas flows responsible for assembling the first galaxies produce the high gas densities that lead to sustained critical accretion rates and hence rapid growth commensurate with the existence of ~10^9 solar mass black holes as early as z~7. We find that under these conditions quasar feedback is not effective at stopping the cold gas from penetrating the central regions and hence cannot quench the accretion until the host galaxy reaches M_halo > 10^{12} solar masses. This cold-flow driven scenario for the formation of quasars implies that they should be ubiquitous in galaxies in the early universe and that major (proto)galaxy mergers are not a requirement for efficient fuel supply and growth, particularly for the earliest SMBHs.

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