The Effects of Magnetic Fields and Outflow Feedback on the Shape and Evolution of the Density Probability Distribution Function in Turbulent Star-forming Clouds
The Effects of Magnetic Fields and Outflow Feedback on the Shape and Evolution of the Density Probability Distribution Function in Turbulent Star-forming Clouds
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DOI：
10.3847/1538-4357/ac4be3
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发表时间：
2021-09
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影响因子：
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通讯作者：
S. Appel;B. Burkhart;V. Semenov;C. Federrath;A. Rosen
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作者：
S. Appel;B. Burkhart;V. Semenov;C. Federrath;A. Rosen
使用一套恒星形成分子云的3D流体动力学模拟，我们研究了密度概率分布函数（PDF）在包括重力，湍流，磁场和原恒星流出和加热时的变化。我们发现，当考虑外流和自重力时，密度PDF不是对数正态的。自引力在高密度下产生幂律尾，而包含来自原恒星流出和加热的恒星反馈在低密度下产生与对数正态分布显著的随时间变化的偏差。与没有流出的模拟相比，有流出的模拟具有过量的扩散气体，表现出增加的平均音速马赫数，并且在整个运行期间保持较慢的星星形成速率（SFR）。我们研究了PDF对数正态峰中的扩散气体、幂律尾中的坍缩气体和恒星之间的质量传递。我们发现，在幂律尾部的质量分数是恒定的，这样，恒星形成的幂律气体在相同的速度，在对数正态部分的气体超越幂律。我们发现，湍流不提供显着的支持，在稠密的气体与幂律尾。当除了驱动湍流之外还包括流出和磁场时，从对数正态到幂律，然后到恒星的质量传递速率变得明显较慢，导致较慢的SFR和较长的耗尽时间。
Using a suite of 3D hydrodynamical simulations of star-forming molecular clouds, we investigate how the density probability distribution function (PDF) changes when including gravity, turbulence, magnetic fields, and protostellar outflows and heating. We find that the density PDF is not lognormal when outflows and self-gravity are considered. Self-gravity produces a power-law tail at high densities, and the inclusion of stellar feedback from protostellar outflows and heating produces significant time-varying deviations from a lognormal distribution at low densities. The simulation with outflows has an excess of diffuse gas compared to the simulations without outflows, exhibits an increased average sonic Mach number, and maintains a slower star formation rate (SFR) over the entire duration of the run. We study the mass transfer between the diffuse gas in the lognormal peak of the PDF, the collapsing gas in the power-law tail, and the stars. We find that the mass fraction in the power-law tail is constant, such that the stars form out of the power-law gas at the same rate at which the gas from the lognormal part replenishes the power law. We find that turbulence does not provide significant support in the dense gas associated with the power-law tail. When including outflows and magnetic fields in addition to driven turbulence, the rate of mass transfer from the lognormal to the power law, and then to the stars, becomes significantly slower, resulting in slower SFRs and longer depletion times.