THE LAUNCHING OF COLD CLOUDS BY GALAXY OUTFLOWS. II. THE ROLE OF THERMAL CONDUCTION
THE LAUNCHING OF COLD CLOUDS BY GALAXY OUTFLOWS. II. THE ROLE OF THERMAL CONDUCTION
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星系外流引发冷云。
DOI：
10.3847/0004-637x/822/1/31
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
E. Scannapieco
中科院分区：
文献类型：
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作者：
M. Brüggen;E. Scannapieco
我们探讨电子热传导对发生在流出星系中的热且快速物质流中的辐射冷却冷云演化的影响。通过对三维自适应网格细化流体动力学模拟进行参数研究，我们发现电子热传导会导致冷云蒸发，但它也可以通过将它们压缩成致密的细丝来延长其寿命。我们区分低柱密度云和高柱密度云，低柱密度云在很短的时间内被破坏，而高柱密度云则具有更长的破坏时间，这是由冲击热能和蒸发之间的平衡决定的。我们提供了云寿命和速度的拟合，可用于星系尺度的流出模拟，其中单个云的演化无法用所需的分辨率进行建模。此外，我们表明，云仅被加速到环境速度的一小部分，因为蒸发压缩导致云对环境流呈现出较小的横截面。这意味着要么磁场必须抑制热传导，要么在星系流出中观察到的冷云不是由从星系携带的冷物质形成的。
We explore the impact of electron thermal conduction on the evolution of radiatively cooled cold clouds embedded in flows of hot and fast material as it occurs in outflowing galaxies. Performing a parameter study of three-dimensional adaptive mesh refinement hydrodynamical simulations, we show that electron thermal conduction causes cold clouds to evaporate, but it can also extend their lifetimes by compressing them into dense filaments. We distinguish between low column-density clouds, which are disrupted on very short times, and high-column density clouds with much longer disruption times that are set by a balance between impinging thermal energy and evaporation. We provide fits to the cloud lifetimes and velocities that can be used in galaxy-scale simulations of outflows in which the evolution of individual clouds cannot be modeled with the required resolution. Moreover, we show that the clouds are only accelerated to a small fraction of the ambient velocity because compression by evaporation causes the clouds to present a small cross-section to the ambient flow. This means that either magnetic fields must suppress thermal conduction, or that the cold clouds observed in galaxy outflows are not formed of cold material carried out from the galaxy.