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arXiv 2203.01508astro-ph.GA
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存在重力、磁场、辐射和外流反馈时湍流云的速度统计

The Velocity Statistics of Turbulent Clouds in the Presence of Gravity, Magnetic fields, Radiation, and Outflow Feedback

Yue Hu, Christoph Federrath, Siyao Xu, Sajay Sunny Mathew

摘要:

分子云内部的湍流、磁场、自引力和恒星反馈的相互作用对于理解恒星的形成至关重要。通过结构函数研究了自重力和外流反馈对湍流速度特性的影响,尺度范围从$\sim$ 0.01 pc到2 pc.我们分析了一系列的三维,磁流体动力学(MHD)模拟恒星团簇形成。我们发现流出反馈可以改变速度波动的尺度,但仍然大致在Kolmogorov和Burgers湍流之间。我们观察到,自引力和原恒星外流增加的速度波动在所有的长度尺度。流出物可将速度波动放大高达$\sim$ 7倍(尺度为$\sim$ 0.01 - 0.2 pc),并将湍流驱动至高达$\sim$ 1 pc的尺度。放大的速度波动提供了更多的支持,以对抗重力,并加强了小尺度的碎裂。自重力的影响在较小的致密团块上更为显著,它将压缩速度分量的分数增加到$\sim$ 0.2 pc的尺度。然而,流出反馈驱动螺线管和压缩模式,但它引起的螺线管模式相对于压缩模式更高的分数。因此,在外流情况下,致密核最终会有稍高比例的螺线管模式。我们发现,在尺度$\sim$ 0.1 - 0.2 pc上,可压缩分数是相当恒定的,约为1/3。增强的速度色散和减少的压缩分数的组合效应有助于降低恒星形成率。

英文摘要:

The interaction of turbulence, magnetic fields, self-gravity, and stellar feedback within molecular clouds is crucial for understanding star formation. We study the effects of self-gravity and outflow feedback on the properties of the turbulent velocity via the structure function over length scales from $\sim$ 0.01 pc to 2 pc. We analyze a series of three-dimensional, magnetohydrodynamical (MHD) simulations of star cluster formation. We find outflow feedback can change the scaling of velocity fluctuations but still roughly being in between Kolmogorov and Burgers turbulence. We observe that self-gravity and protostellar outflows increase the velocity fluctuations over all length scales. Outflows can amplify the velocity fluctuations by up to a factor of $\sim$7 on scales $\sim$ 0.01 - 0.2 pc and drive turbulence up to a scale of $\sim$ 1 pc. The amplified velocity fluctuations provide more support against gravity and enhance fragmentation on small scales. The self-gravity's effect is more significant on smaller dense clumps and it increases the fraction of the compressive velocity component up to a scale of $\sim$ 0.2 pc. However, outflow feedback drives both solenoidal and compressive modes, but it induces a higher fraction of solenoidal modes relative to compressive modes. Thus, with outflows, the dense core ends up with a slightly higher fraction of solenoidal modes. We find that the compressible fraction is fairly constant with about 1/3 on scales $\sim$ 0.1 - 0.2 pc. The combined effect of enhanced velocity dispersion and reduced compressive fraction contributes to a reduction in the star formation rate.

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