Radiation-hydrodynamic Simulations of Spherical Protostellar Collapse for Very Low-mass Objects
Radiation-hydrodynamic Simulations of Spherical Protostellar Collapse for Very Low-mass Objects
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DOI：
10.3847/1538-4357/aaee81
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发表时间：
2018-11
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影响因子：
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通讯作者：
Torsten Stamer;S. Inutsuka
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作者：
Torsten Stamer;S. Inutsuka
我们进行辐射流体动力学模拟的原恒星坍缩在球对称，特别侧重于非常低的质量物体，即，褐矮星和亚褐矮星。包括一个现实的状态方程，其中包括氢离解的影响，允许从开始的崩溃，直到形成的原恒星的完整过程的建模。我们解决了依赖于频率的辐射传输方程没有任何扩散近似，使用现实的尘埃和气体的不透明度。我们的研究结果表明，原恒星的性质基本上是独立的初始条件，这以前只被证实为更高的质量范围。然而，对于非常低的质量初始条件下，我们发现，第一个核心阶段的崩溃显示出一些显着的差异，在时间演化，与第一个核心寿命急剧增加，因为从周围的信封吸积率降低。我们考虑这一点的观测影响。我们还调查了相反的情况下，崩溃没有任何第一个核心阶段，这可能会发生非常不稳定的初始条件。在附录中，我们描述了一个严重的数值问题，它导致原恒星形成后的非物理膨胀，这可能会影响其他类似的自引力坍缩计算。我们解释了非物理行为的起源，并提出了一个解决方案，可用于类似的调查。
We perform radiation-hydrodynamical simulations of protostellar collapse in spherical symmetry, with a special focus on very low-mass objects, i.e., brown dwarfs and sub-brown dwarfs. The inclusion of a realistic equation of state, which includes the effect of hydrogen dissociation, allows for a modeling of the complete process from the beginning of the collapse until the formation of the protostar. We solve the frequency-dependent radiative transfer equation without any diffusion approximation, using realistic dust and gas opacities. Our results show that the properties of the protostar are essentially independent of the initial conditions, which had previously only been confirmed for higher mass ranges. For very low-mass initial conditions, however, we find that the first core phase of the collapse shows some significant differences in the time evolution, with the first core lifetime increasing dramatically because of the reduced accretion rate from the surrounding envelope. We consider the observational implications of this. We also investigate the opposite case of a collapse without any first core phase, which may occur for very unstable initial conditions. In the Appendix, we describe a severe numerical problem that causes an unphysical expansion after the formation of the protostar, which may affect other attempts at similar calculations of self-gravitational collapse. We explain the origin of the unphysical behavior and present a solution that can be used in similar investigations.