Massive black hole binary inspiral and spin evolution in a cosmological framework
Massive black hole binary inspiral and spin evolution in a cosmological framework
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DOI：
10.1093/mnras/staa3826
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发表时间：
2020-06
影响因子：
4.8
通讯作者：
M. Sayeb;L. Blecha;L. Kelley;D. Gerosa;M. Kesden;J. Thomas
中科院分区：
文献类型：
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作者：
M. Sayeb;L. Blecha;L. Kelley;D. Gerosa;M. Kesden;J. Thomas
大质量黑洞（MBH）双星的螺旋时间尺度是不确定的，它们的自旋甚至更不受约束。自旋错位在引力辐射中引入了不对称性，这给合并的MBH带来了反冲反冲。了解MBH双星自旋的演化过程对于确定它们的反冲速度、用激光干涉仪空间天线探测到的引力波波形以及它们在星系中的留存率至关重要。在这里，我们介绍了一个亚分辨率模型的气体和引力波（GW）驱动的MBH二进制自旋演化吸积MBH从插图宇宙流体动力学模拟。我们还通过动力学摩擦，恒星散射，粘性气体阻力和GW排放模型的二进制inspiral。我们的模型假设环双星盘总是从双星中移除角动量。它还假设微分吸积，这将导致更大的调整二级MBH自旋不等质量合并。我们发现，在我们的人口中，47%的MBH合并z = 0。其中，有19%的小学和10%的小学合并时，在我们的基准模型与初始偏心率为0.6和吸积率从插图的错位。然而，MBH失调分数强烈依赖于吸积盘参数。在较厚的圆盘中，将吸积率降低100倍，分别产生79%和42%的初级和次级不对准。即使在更保守的基准模型中，也有超过12%的双星经历了大于500 km s-1的反冲，这可能会使它们至少暂时离开星系核。我们还发现，大量的系统经历强进动。
Massive black hole (MBH) binary inspiral time-scales are uncertain, and their spins are even more poorly constrained. Spin misalignment introduces asymmetry in the gravitational radiation, which imparts a recoil kick to the merged MBH. Understanding how MBH binary spins evolve is crucial for determining their recoil velocities, their gravitational wave (GW) waveforms detectable with Laser Interferometer Space Antenna, and their retention rate in galaxies. Here, we introduce a sub-resolution model for gas- and gravitational wave (GW)-driven MBH binary spin evolution using accreting MBHs from the Illustris cosmological hydrodynamic simulations. We also model binary inspiral via dynamical friction, stellar scattering, viscous gas drag, and GW emission. Our model assumes that the circumbinary disc always removes angular momentum from the binary. It also assumes differential accretion, which causes greater alignment of the secondary MBH spin in unequal-mass mergers. We find that 47 per cent of the MBHs in our population merge by z = 0. Of these, 19 per cent have misaligned primaries and 10 per cent have misaligned secondaries at the time of merger in our fiducial model with initial eccentricity of 0.6 and accretion rates from Illustris. The MBH misalignment fraction depends strongly on the accretion disc parameters, however. Reducing accretion rates by a factor of 100, in a thicker disc, yields 79 and 42 per cent misalignment for primaries and secondaries, respectively. Even in the more conservative fiducial model, more than 12 per cent of binaries experience recoils of >500 km s−1, which could displace them at least temporarily from galactic nuclei. We additionally find that a significant number of systems experience strong precession.