Nature2014-06-24 4:41 PM

一个超大质量黑洞的生长模式 Reflection from the strong gravity regime in a lensed quasar at redshift z = 0.658

论文摘要 

本文报告了对一个超大质量黑洞的旋转所做的直接测量,该黑洞与我们的距离从宇宙层面来说比较远。对与我们的距离超过60亿光年、红移值为0.658、具有四倍透镜效应的类星体的由反射主导的光谱所做的新观测、连同对存档的X-射线数据所做的分析显示,它正在快速转动。它的辐射大部分来自与该黑洞的距离在三个或以下引力半径之内的一个小区域。一个黑洞的旋转可以提供它与其主星系通过宇宙时间共同演变的一个记录,同时这些新数据表明,该黑洞(同那些以前在红移值大于2处观测到的一样)是通过相干吸积生长的,而不是以混沌方式生长的。

Abstract 

The co-evolution of a supermassive black hole with its host galaxy through cosmic time is encoded in its spin. At z > 2, supermassive black holes are thought to grow mostly by merger-driven accretion leading to high spin. It is not known, however, whether below z ≈ 1 these black holes continue to grow by coherent accretion or in a chaotic manner, though clear differences are predicted in their spin evolution. An established method of measuring the spin of black holes is through the study of relativistic reflection features from the inner accretion disk. Owing to their greater distances from Earth, there has hitherto been no significant detection of relativistic reflection features in a moderate-redshift quasar. Here we report an analysis of archival X-ray data together with a deep observation of a gravitationally lensed quasar at z = 0.658. The emission originates within three or fewer gravitational radii from the black hole, implying a spin parameter (a measure of how fast the black hole is rotating) of a =   at the 3σ confidence level and a > 0.66 at the 5σ level. The high spin found here is indicative of growth by coherent accretion for this black hole, and suggests that black-hole growth at 0.5 ≤ z ≤ 1 occurs principally by coherent rather than chaotic accretion episodes.

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