arXiv 1207.69892012-07-30astro-ph.SRastro-ph.GA

分子云的碎裂与演化。III：粉尘和气体能量学的影响

Fragmentation and Evolution of Molecular Clouds. III: The Effect of Dust and Gas Energetics

Hugo Martel, Andrea Urban, Neal J. Evans

备注：: 10 figures, 3 colored. Accepted for publication in ApJ
DOI：: 10.1088/0004-637X/757/1/59

摘要：

尘埃和气体能量学被纳入恒星形成的星团尺度模拟，以研究加热和冷却对恒星形成过程的影响。我们建立在我们以前的工作，分别计算尘埃和气体的温度。尘埃的温度是由嵌入恒星的加热和尘埃辐射之间的辐射平衡决定的。气体温度是使用能量率平衡算法，其中包括分子冷却，尘埃气体碰撞能量转移，和宇宙射线电离。碎片化的过程与气体温度被设置为尘埃温度的模拟大致相似，但存在差异。下沉粒子周围区域的结构具有与0类天体相似的性质，但平均而言，下沉速度和质量吸积率高于仅形成低质量恒星的区域。气体和尘埃的温度有复杂的分布，不能很好地模拟近似，忽略了详细的热物理。密度和动力学温度之间没有简单的关系。特别地，高密度区域具有大范围的温度，这由它们相对于加热源的位置确定。总光度低估了这些早期阶段的恒星形成率，在电离源被包括在内之前，一个数量级。正如我们以前的工作所预测的那样，当包括改进的热物理学时，会形成更多的中等质量天体，但由此产生的IMF仍然有太少的低质量恒星。然而，如果我们考虑最近关于核心到恒星效率的证据，与IMF的匹配得到了改善。

英文摘要：

Dust and gas energetics are incorporated into a cluster-scale simulation of star formation in order to study the effect of heating and cooling on the star formation process. We build on our previous work by calculating separately the dust and gas temperatures. The dust temperature is set by radiative equilibrium between heating by embedded stars and radiation from dust. The gas temperature is determined using an energy-rate balance algorithm which includes molecular cooling, dust-gas collisional energy transfer, and cosmic-ray ionization. The fragmentation proceeds roughly similarly to simulations in which the gas temperature is set to the dust temperature, but there are differences. The structure of regions around sink particles have properties similar to those of Class 0 objects, but the infall speeds and mass accretion rates were, on average, higher than those seen for regions forming only low-mass stars. The gas and dust temperature have complex distributions not well modeled by approximations that ignore the detailed thermal physics. There is no simple relationship between density and kinetic temperature. In particular, high density regions have a large range of temperatures, determined by their location relative to heating sources. The total luminosity underestimates the star formation rate at these early stages, before ionizing sources are included, by an order of magnitude. As predicted in our previous work, a larger number of intermediate mass objects form when improved thermal physics is included, but the resulting IMF still has too few low mass stars. However, if we consider recent evidence on core-to-star efficiencies, the match to the IMF is improved.

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