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arXiv 1004.3785astro-ph.CO
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模拟超大质量黑洞附近气体吸积和Angular Momentum的测量

Measuring Gas Accretion and Angular Momentum near Simulated Supermassive Black Holes

Robyn Levine, Nickolay Y. Gnedin, Andrew J. S. Hamilton

摘要:

利用动态范围超过1000万的宇宙学模拟,我们研究了气体质量和角动量通过含有超大质量黑洞(SMBH)的盘状星系的环核区域的输运。模拟遵循星系演化的相对静止阶段(没有合并),并且没有活动星系核(AGN)的反馈,作为使用最先进的高分辨率宇宙学模拟来模拟星系和黑洞共同演化的第一阶段的一部分。我们提出了在不同的红移(z=6,4和3)和三个不同的黑洞质量(3000万,9000万和3亿太阳质量;在z=4),以及模拟,包括一个处方,近似在dennis区域的光学厚冷却的模拟结果。整个环核盘的内部气体质量作为时间的函数表现出瞬态和混沌行为。内部气体质量的傅立叶变换在整个区域内遵循斜率为-1的幂律,这表明,在没有星系合并和活动星系核反馈的影响下,质量波动是随机的,在每次模拟的持续时间(~ 1-2百万年)内没有首选的吸积时间尺度。在小于100万年的时间尺度上,气体盘的角动量相对于盘在千秒差距尺度上改变方向,反映了环核区域的混沌和瞬态气体动力学。由于环核盘的动力学状态而向内驱动的气体团,可能在确定SMBH的自旋演化中发挥重要作用,正如在随机吸积情景中所建议的那样。

英文摘要:

Using cosmological simulations with a dynamic range in excess of 10 million, we study the transport of gas mass and angular momentum through the circumnuclear region of a disk galaxy containing a supermassive black hole (SMBH). The simulations follow fueling over relatively quiescent phases of the galaxy's evolution (no mergers) and without feedback from active galactic nuclei (AGNs), as part of the first stage of using state-of-the-art, high-resolution cosmological simulations to model galaxy and black hole co-evolution. We present results from simulations at different redshifts (z=6, 4, and 3) and three different black hole masses (30 million, 90 million, and 300 million solar masses; at z=4), as well as a simulation including a prescription that approximates optically thick cooling in the densest regions. The interior gas mass throughout the circumnuclear disk shows transient and chaotic behavior as a function of time. The Fourier transform of the interior gas mass follows a power law with slope -1 throughout the region, indicating that, in the absence of the effects of galaxy mergers and AGN feedback, mass fluctuations are stochastic with no preferred timescale for accretion over the duration of each simulation (~ 1-2 Myr). The angular momentum of the gas disk changes direction relative to the disk on kiloparsec scales over timescales less than 1 Myr, reflecting the chaotic and transient gas dynamics of the circumnuclear region. Infalling clumps of gas, which are driven inward as a result of the dynamical state of the circumnuclear disk, may play an important role in determining the spin evolution of an SMBH, as has been suggested in stochastic accretion scenarios.

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