大质量黑洞自旋中宇宙演化的证据
Evidence for cosmic evolution in the spin of the most massive black holes
摘要：
我们使用的结果，从模拟生产的磁流体动力学喷流周围的黑洞推导出宇宙的自旋历史的最大质量的黑洞。我们假设，喷流生产的效率是一个单调的函数的自旋a，由模拟，吸积流的几何形状是类似的厚类星体吸积接近爱丁顿比和低激发射电星系吸积在非常小的爱丁顿率。我们利用Mbh>~10^8 Msol的超大质量黑洞的喷流功率和辐射吸积功率的共动密度之比来估计特征自旋a的宇宙历史。这一比值随z的减小而增大，与z~0的活动星系核比z~2的活动星系核具有更高的自旋（典型值分别为a~0.35-0.95和a~0.0-0.25）的图像相一致。我们讨论了吸积和合并在Mbh>~10^8 Msol的超大质量黑洞生长中的相对重要性。
英文摘要：
We use results from simulations of the production of magnetohydrodynamic jets around black holes to derive the cosmic spin history of the most massive black holes. We assume that the efficiency of jet production is a monotonic function of spin a, as given by the simulations, and that the accretion flow geometry is similarly thick for quasars accreting close to the Eddington ratio and for low-excitation radio galaxies accreting at very small Eddington rates. We use the ratio of the comoving densities of the jet power and the radiated accretion power associated with supermassive black holes with Mbh>~10^8 Msol to estimate the cosmic history of the characteristic spin a. The evolution of this ratio, which increases with decreasing z, is consistent with a picture where the z~0 active galactic nuclei have typically higher spins than those at z~2 (with typical values a~0.35-0.95 and a~0.0-0.25 respectively). We discuss the implications in terms of the relative importance of accretion and mergers in the growth of supermassive black holes with Mbh>~10^8 Msol.
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