PRESTELLAR CORE FORMATION, EVOLUTION, AND ACCRETION FROM GRAVITATIONAL FRAGMENTATION IN TURBULENT CONVERGING FLOWS
PRESTELLAR CORE FORMATION, EVOLUTION, AND ACCRETION FROM GRAVITATIONAL FRAGMENTATION IN TURBULENT CONVERGING FLOWS
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DOI：
10.1088/0004-637x/806/1/31
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发表时间：
2015-04
期刊：
影响因子：
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通讯作者：
M. Gong;E. Ostriker
中科院分区：
文献类型：
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作者：
M. Gong;E. Ostriker
我们基于三维流体动力学模拟研究了星前核的形成和吸积。我们的模拟代表了巨型分子云中的局部∼1 PC区域，在那里超音速湍流会聚，触发了激波后层中的恒星形成。我们包括湍流和自重，应用了汇粒子技术，并探索了一系列流入马赫数=2−16？识别和比较了两组岩心：T1岩心从每次模拟的时间快照中识别，并在单个云图中表示致密结构；Tcoll岩芯在其各自的坍塌时间识别，并表示用于吸积的初始质量储集层。我们发现，核和细丝同时形成和演化。在核坍塌阶段，存在一个定义明确的、收敛的等温碎裂特征质量，它与激波后压力下的临界Bonnor-Ebert质量相当。与观测到的恒星初始质量函数相比，TCOIL核的核质量函数(CMF)显示出大质量核(≳7 M☉？>；)的亏损。然而，T1岩心的CMF与观测到的CMF相似，并且包括许多重力稳定的低质量岩心。T1核和TCOL核之间的差异表明，来自观测到的CMF的完整样本可能不会演化成原恒星。在整个模拟过程中，单个下沉颗粒以大致恒定的速度聚集，即使在最初的质量储集层被吸积之后，每次自由落体时间也会获得一个核心质量。在以后的时间里，高质量的水槽比低质量的水槽按比例获得更多的质量。由于块状密度结构落入水槽中，吸积率出现了暴发。
We investigate prestellar core formation and accretion based on three-dimensional hydrodynamic simulations. Our simulations represent local ∼1 pc regions within giant molecular clouds where a supersonic turbulent flow converges, triggering star formation in the post-shock layer. We include turbulence and self-gravity, applying sink particle techniques, and explore a range of inflow Mach numbers = 2 − 16 ?> . Two sets of cores are identified and compared: t1 cores are identified from a time snapshot in each simulation and represent dense structures in a single cloud map; tcoll cores are identified at their individual time of collapse and represent the initial mass reservoir for accretion. We find that cores and filaments form and evolve at the same time. At the stage of core collapse, there is a well-defined, converged characteristic mass for isothermal fragmentation that is comparable to the critical Bonnor–Ebert mass at the post-shock pressure. The core mass functions (CMFs) of tcoll cores show a deficit of high-mass cores ( ≳ 7 M ☉ ?> ) compared to the observed stellar initial mass function (IMF). However, the CMFs of t1 cores are similar to the observed CMFs and include many low-mass cores that are gravitationally stable. The difference between t1 cores and tcoll cores suggests that the full sample from observed CMFs may not evolve into protostars. Individual sink particles accrete at a roughly constant rate throughout the simulations, gaining one core mass per freefall time even after the initial mass reservoir is accreted. High-mass sinks gain proportionally more mass at later times than low-mass sinks. There are outbursts in accretion rates, resulting from clumpy density structures falling into the sinks.