arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 1009.0945astro-ph.CO
收藏

早期宇宙重子超密度的非线性演化:数值模拟的初始条件

The nonlinear evolution of baryonic overdensities in the early universe: Initial conditions of numerical simulations

Smadar Naoz, Naoki Yoshida, Rennan Barkana

摘要:

我们运行非常大的宇宙学N体流体动力学模拟,以统计研究早期暗物质晕中的重子分数。我们批判性地研究了初始条件的差异如何影响红移范围z = 11- 21的气体分数。我们测试了三种不同的线性功率谱的初始条件:(1)一个完整的加热模型,这是我们的基准模型;根据Naoz & Barkana(2005),这个模型正确地遵循了超密度的演变,特别是包括由于来自CMB的康普顿加热引起的气体的声速的空间变化。(2)一个等δ模型,假设初始重子涨落等于暗物质的涨落,同时保持总物质的σ 8。(3)平均cs模型,假定气体的声速均匀。后两种模型在文献中经常使用。在我们的模拟中,我们计算了一个大样本的晕的重子分数。我们的基准模型表明,在再电离和显著的恒星加热发生之前,在整个形成过程中,小晕保持其大部分重子所需的最小质量约为3 * 10^4 Msun。然而,替代模型产生了错误的(高出约50%)最小质量,因为系统保留了初始条件的记忆。我们还证明了这一点,使用“过滤质量”从线性理论,准确地描述了整个模拟红移范围内的重子分数的演变。

英文摘要:

We run very large cosmological N-body hydrodynamical simulations in order to study statistically the baryon fractions in early dark matter halos. We critically examine how differences in the initial conditions affect the gas fraction in the redshift range z = 11--21. We test three different linear power spectra for the initial conditions: (1) A complete heating model, which is our fiducial model; this model follows the evolution of overdensities correctly, according to Naoz & Barkana (2005), in particular including the spatial variation of the speed of sound of the gas due to Compton heating from the CMB. (2) An equal-δ model, which assumes that the initial baryon fluctuations are equal to those of the dark matter, while conserving sigma8 of the total matter. (3) A mean cs model, which assumes a uniform speed of sound of the gas. The latter two models are often used in the literature. We calculate the baryon fractions for a large sample of halos in our simulations. Our fiducial model implies that before reionization and significant stellar heating took place, the minimum mass needed for a minihalo to keep most of its baryons throughout its formation was ~ 3 * 10^4 Msun. However, the alternative models yield a wrong (higher by about 50%) minimum mass, since the system retains a memory of the initial conditions. We also demonstrate this using the "filtering mass" from linear theory, which accurately describes the evolution of the baryon fraction throughout the simulated redshift range.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑