Probing the early growth of supermassive black holes with the environment of high-redshift quasars

这项工作旨在探索超大质量黑洞在早期宇宙中的早期增长。可以超过数百万个太阳质量的超大质量黑洞被发现无处不在，位于局部大质量星系的中心，比如我们的银河系。这些怪物是如何形成和进化的？理论工作提出了两种可能的起源：一种是重黑洞种子，另一种是典型的恒星质量的强生长黑洞种子。在这项工作中，由于超超素数-凸轮-斯巴鲁战略计划的广泛和深入的成像，我们在红移4(大爆炸后约1.5 Gyr)的宽光度范围内构建了大量类星体(即快速增长的超大质量黑洞)。与前人的工作相比，这项工作将类星体样本的星等覆盖范围向深端扩展了2个数量级以上。我们利用Keck/Deimos和AAT/AAOmega光谱仪估算了超大质量黑洞的质量和艾丁顿比(可用来量化吸积率)。在本财年，我们利用这些信息追溯了他们可能的增长轨迹。结果表明：1)这些类星体需要一个沉重的黑洞种子才能形成，即使在极端的生长模式下也是如此；2)这些类星体正倾向于将它们的旺盛生长“关闭”为随后的间歇性生长。

This work aims at probing the early growth of supermassive black holes in the early universe. Supermassive black holes, which can be over millions of solar masses, are found to be ubiquitous at the center of local massive galaxies, like our Milky Way. How are these monsters formed and evolved? Theoretical works suggest two possible origins: a heavy black hole seed or a typical stellar-mass black hole seed with powerful growth.In this work, thanks to the wide and deep imaging of the Hyper Suprime-Cam Subaru Strategic Program, we constructed a large sample of quasars (i.e., rapidly growing supermassive black holes) over a wide luminosity range at redshift 4 (around 1.5 Gyr after the BigBang). Compared to previous works, this work extends the magnitude coverage of quasar sample towards the deep end by over 2 order of magnitude. The wide magnitude range makes our quasar sample more numerous, and it can provide less-biased view on early growth of supermassive black holes.We estimated their black hole mass and Eddington ratio (which can be used to quantify accretion rate) using Keck/DEIMOS and AAT/AAOmega spectrograph. In this fiscal year, we utilized the information to trace back their possible growth tracks. Results suggest 1) those quasars need a heavy black hole seed to be formed even under the extreme growing mode; and 2) those quasars are tending to "shut-down" their vigorous growth to episodic growth afterwards.