Angular Momentum Transport in Early-formed Objects by Cosmic Background Radiation: Radiation-hydrodynamical Approach
Angular Momentum Transport in Early-formed Objects by Cosmic Background Radiation: Radiation-hydrodynamical Approach
复制标题
宇宙背景辐射早期形成物体的角动量传输：辐射流体动力学方法
DOI：
10.1086/304489
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
M. Umemura
中科院分区：
文献类型：
--
作者：
Tohru Tsuribe;M. Umemura
研究了宇宙重组后不久，宇宙背景辐射（CBR）对早期形成天体辐射力的影响。特别是，我们感兴趣的角动量输运在大规模磁盘，源于潮汐旋转的密度波动。CBR的辐射力是通过求解辐射传输方程和包括汤姆逊散射计算的，假设一个磁盘是局部近似为一个平面平行介质在纵向运动。作为一种数值方法，我们采用可变爱丁顿因子方法。结果表明，即使辐射扩散有效，CBR提取角动量的效率也随光学深度呈指数下降。这意味着，就动量或角动量输运而言，运动介质中的光子散射过程与纯吸收过程一样。由于目前的影响，早期形成的磁盘的自旋概率的分布可以显着修改的存在下，强CBR。由大自旋参数（λ > 0.05）产生的光学薄圆盘会释放角动量，直到它变得光学厚，导致λ ~ 0.05，几乎与物体的质量尺度和初始功率谱无关。此外，CBR力可能有助于增强剪切粘度的影响，从而使种子黑洞在z > 10时形成，以解释类星体的形成。
The effects of radiation force by the cosmic background radiation (CBR) on early-formed objects shortly after the cosmological recombination are explored. In particular, we are interested in the angular momentum transport in massive disks that originate from tidally spun-up density fluctuations. The radiation force by the CBR is calculated by solving the radiative transfer equation and including Thomson scattering, under the assumption that a disk is locally approximated to be a plane-parallel medium in longitudinal motion. As a numerical technique, we employ a variable Eddington factor method. The results show that the efficiency of angular momentum extraction by the CBR decreases exponentially with optical depth even if the radiative diffusion is effective. This implies that the photon-scattering process in moving media proceeds just like the pure absorption process as far as momentum or angular momentum transport is concerned. Because of the present effects, the distributions of the spin probability of early-formed disks could be significantly modified in the presence of the strong CBR. An optically thin disk originating from a large spin parameter (λ > 0.05) would shed angular momentum until it becomes optically thick, resulting in λ ~ 0.05, almost regardless of mass scales of objects and the initial power spectrum. Also, the CBR force likely helps to enhance the effects of shear viscosity, thereby enabling a seed black hole form at z > 10 to account for quasar formation.