卷入麻烦：热超新星驱动的银河风中冷云的加速和破坏
Entrainment in Trouble: Cool Cloud Acceleration and Destruction in Hot Supernova-Driven Galactic Winds
摘要：
在恒星形成的星系中，重叠的超新星的有效热化可能会产生一种超新星加热的流体，这种流体驱动着星系风。对于从高分辨率模拟（忽略磁场）云粉碎的时间尺度的基准假设，我们表明，从$T_{c}\sim 10^{2}-10^{4}$ K的温度在银河风的发射和吸收看到的冷云不能被加速到观测速度的冲压压力的热风。考虑到径向结构的热流和重力，我们表明，这一结论适用于广泛的星系，云，和热风的属性。这一发现质疑了流行的图片，即在银河风中看到的冷原子气体被热流夹带和加速。考虑到冲压压力加速的这些困难，我们讨论了高速冷气体流出的起源的替代模型。另一种可能性是，冷云中的磁场非常重要，可以延长云的寿命。对于$T_{c}=10^{3}$ \，K和$10^{4}$ \，K云，我们表明，如果传导蒸发可以忽略不计，云粉碎的时间尺度必须分别为$\sim15$和5倍长，从流体动力学模拟的值，以冷云的速度，以达到观察到的。
英文摘要：
Efficient thermalization of overlapping supernovae within star-forming galaxies may produce a supernova-heated fluid that drives galactic winds. For fiducial assumptions about the timescale for cloud shredding from high-resolution simulations (which neglect magnetic fields) we show that cool clouds with temperature from $T_{c}\sim 10^{2}-10^{4}$ K seen in emission and absorption in galactic winds cannot be accelerated to observed velocities by the ram pressure of a hot wind. Taking into account both the radial structure of the hot flow and gravity, we show that this conclusion holds over a wide range of galaxy, cloud, and hot wind properties. This finding calls into question the prevailing picture whereby the cool atomic gas seen in galactic winds is entrained and accelerated by the hot flow. Given these difficulties with ram pressure acceleration, we discuss alternative models for the origin of high velocity cool gas outflows. Another possibility is that magnetic fields in cool clouds are sufficiently important that they prolong the cloud's life. For $T_{c}=10^{3}$\,K and $10^{4}$\,K clouds, we show that if conductive evaporation can be neglected, the cloud shredding timescale must be $\sim15$ and 5 times longer, respectively, than the values from hydrodynamical simulations in order for cool cloud velocities to reach those seen in observations.
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