arXiv 0908.41292009-08-28astro-ph.SR

外流反馈调节秒差距尺度星系团中大质量恒星的形成

Outflow Feedback Regulated Massive Star Formation in Parsec-Scale Cluster Forming Clumps

Peng Wang, Zhi-Yun Li, Tom Abel, Fumitaka Nakamura

备注：: 36 pages, 9 figures, submitted to ApJ, contact the authors for movies of the simulations
发表信息：: Astrophys.J.709:27-41,2010
DOI：: 10.1088/0004-637X/709/1/27

摘要：

（节略）我们研究了大质量恒星形成的湍流，磁化，秒差距尺度的分子云团块，包括原恒星流出反馈使用基于恩佐的MHD模拟吸积汇粒子和有效分辨率$2048^3$。我们发现，在没有磁场和外流反馈的调节下，大质量恒星很容易形成在一个湍流的、适度浓缩的$\sim 1,600$太阳质量的星团中，以及一个由数百颗低质量恒星组成的星团。大质量恒星的高速供给来自：（1）早期大规模湍流压缩产生的瞬时致密细丝，以及（2）晚期湍流衰变导致的团簇范围的全球坍缩。在这两种情况下，大质量恒星的大部分质量都是由围绕恒星的0.1 pc大小的“核心”外部提供的。在我们的模拟中，这颗大质量恒星是由团块而不是核心喂养的。对大规模进食的需求使得大质量恒星的形成倾向于通过流出反馈进行调节，这直接与进食过程相反。外流通过打破在早期为大质量恒星形成提供燃料的致密细丝，并通过集体减缓在晚期为大质量恒星形成提供燃料的全球崩溃，降低了大质量恒星的质量吸积率。后者是由一个中等强度的磁场在观察范围内的帮助。我们的结论是，在我们模拟的湍流，磁化，秒差距尺度的团块大质量恒星的形成是流出调节和团块喂养（简称ORCF）。一个重要的含义是，在致密星团中形成的低质量恒星可以通过对星团动力学的流出反馈影响同一星团中大质量恒星的形成。

英文摘要：

(Abridged) We investigate massive star formation in turbulent, magnetized, parsec-scale clumps of molecular clouds including protostellar outflow feedback using Enzo-based MHD simulations with accreting sink particles and effective resolution $2048^3$. We find that, in the absence of regulation by magnetic fields and outflow feedback, massive stars form readily in a turbulent, moderately condensed clump of $\sim 1,600$ solar masses, along with a cluster of hundreds of lower mass stars. The massive stars are fed at high rates by (1) transient dense filaments produced by large-scale turbulent compression at early times, and (2) by the clump-wide global collapse resulting from turbulence decay at late times. In both cases, the bulk of the massive star's mass is supplied from outside a 0.1 pc-sized "core" that surrounds the star. In our simulation, the massive star is clump-fed rather than core-fed. The need for large-scale feeding makes the massive star formation prone to regulation by outflow feedback, which directly opposes the feeding processes. The outflows reduce the mass accretion rates onto the massive stars by breaking up the dense filaments that feed the massive star formation at early times, and by collectively slowing down the global collapse that fuel the massive star formation at late times. The latter is aided by a moderate magnetic field of strength in the observed range. We conclude that the massive star formation in our simulated turbulent, magnetized, parsec-scale clump is outflow-regulated and clump-fed (ORCF for short). An important implication is that the formation of low-mass stars in a dense clump can affect the formation of massive stars in the same clump, through their outflow feedback on the clump dynamics.

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