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arXiv 1509.05910astro-ph.GAastro-ph.SR
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自引力湍流中的坍缩

Collapse in Self-gravitating Turbulent Fluids

Daniel W. Murray, Philip Chang, Norman W. Murray, John Pittman

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22 pages, 31 figures, Accepted to Monthly Notices of the Royal Astronomical Society
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摘要：

在最近的数值模拟中发现的一些工人的非线性恒星形成效率的启发，我们进行高分辨率自适应网格细化模拟恒星形成的自引力的恶性驱动气体。当我们跟踪这种气体的坍缩过程时，我们发现流动的特征在两个半径处发生变化，一个是盘半径$r_d$，另一个半径是封闭气体质量超过恒星质量的半径$r_*$。吸积从大尺度开始，向内作用。根据最近的分析工作，我们发现密度演化为一个固定的吸引子，$ρ(r,t ) \rightarrow ρ(r)$，对于$r_d<r<r_*$ ;质量流通过这个结构到一个偶尔的引力不稳定盘，并从那里到恒星。在大部分的模拟箱中我们发现随机运动的$v_T \sim r^p$与$p \sim 0.5$，符合Larson的尺寸-线宽关系。在大质量恒星形成区附近，我们发现了$ p \sim 0.2-0.3$，正如观测所见。对于$r<r_*$，$v_T$向内增加，$p=-1/2$。最后，我们发现，总恒星质量$M_*(t)\sim t^2$与以前的数值和分析工作，表明一个非线性的恒星形成率。

英文摘要：

Motivated by the nonlinear star formation efficiency found in recent numerical simulations by a number of workers, we perform high-resolution adaptive mesh refinement simulations of star formation in self-gravitating turbulently driven gas. As we follow the collapse of this gas, we find that the character of the flow changes at two radii, the disk radius $r_d$, and the radius $r_*$ where the enclosed gas mass exceeds the stellar mass. Accretion starts at large scales and works inwards. In line with recent analytical work, we find that the density evolves to a fixed attractor, $ρ(r,t ) \rightarrow ρ(r)$, for $r_d<r<r_*$; mass flows through this structure onto a sporadically gravitationally unstable disk, and from thence onto the star. In the bulk of the simulation box we find that the random motions $v_T \sim r^p$ with $p \sim 0.5$, in agreement with Larson's size-linewidth relation. In the vicinity of massive star forming regions we find $ p \sim 0.2-0.3$, as seen in observations. For $r<r_*$, $v_T$ increases inward, with $p=-1/2$. Finally, we find that the total stellar mass $M_*(t)\sim t^2$ in line with previous numerical and analytic work that suggests a nonlinear rate of star formation.

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