Accretion in Gravitationally Contracting Clouds
Accretion in Gravitationally Contracting Clouds
复制标题
引力收缩云的吸积
DOI：
10.1093/pasj/48.5.l97
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发表时间：
1996
影响因子：
2.3
通讯作者：
K. Tomisaka
中科院分区：
文献类型：
--
作者：
K. Tomisaka
使用磁流体动力学模拟和嵌套网格技术研究了收缩磁化等温云中的吸积流。首先，星际磁化云经历“失控塌陷”阶段，其中中心密度在有限的时间尺度内急剧增加。最后，它进入吸积阶段，流入的物质吸积到中心高密度盘或新生恒星上。我们发现吸积率达到 (4 - 40) $\times c_s^3/G$，其中 $c_s$ 和 $G$ 分别表示等温声速和引力常数。这比静水等温球形云的标准吸积率 $0.975c_s^3/G$ 大得多 (Shu 1977, AAA19.065.044)。由于在失控阶段获得的额外坠落速度（$\sim 2 c_s$）的影响，吸积率得到提高。与 Shu 的解决方案相比，该速率随时间下降，但保持 $\gtsim 2.5 c_s^3/G$。还讨论了在 L1551 IRS 5 和 HL Tau 等原恒星周围观测到的气体流入率。
Accretion flow in a contracting magnetized isothermal cloud was studied using magnetohydrodynamical simulations and a nested grid technique. First, the interstellar magnetized cloud experiences a ``runaway collapse'' phase, in which the central density increases drastically within a finite time scale. Finally, it enters an accretion phase, in which inflowing matter accretes onto a central high-density disk or a new-born star. We found that the accretion rate reaches (4 -- 40) $\times c_s^3/G$, where $c_s$ and $G$ represent the isothermal sound speed and the gravitational constant, respectively. This is much larger than the standard accretion rate of $0.975c_s^3/G$ for a hydrostatic isothermal spherical cloud (Shu 1977, AAA19.065.044). Due to the effect of an extra infall velocity achieved in the runaway phase ($\sim 2 c_s$), the accretion rate is boosted. This rate declines with time in contrast to Shu's solution, but keeps $\gtsim 2.5 c_s^3/G$. The observed gas infall rate around proto-stars such as L1551 IRS 5 and HL Tau is also discussed.