论文标题
冷却问题中多相气体的生长和结构
Growth and structure of multiphase gas in the cloud-crushing problem with cooling
论文作者
论文摘要
我们重新审查了散热冷却的云灌溉设置中致密/冷气的生长问题。密集云与弥漫介质之间的相对运动在短冷却时间内产生混合气体的湍流边界层。这种混合气体可能解释了在各种来源（例如圆形培养基和银河/恒星/AGN流出）中观察到的吸收/发射线范围的无处不在。最近，Gronke＆OH表明，混合气体的有效辐射冷却会导致致密云的持续生长。他们提出了云量的阈值，以增长密集气体的生长，这与Li等人的最新作品相矛盾。 ＆Sparre等。这些阈值在质量上有所不同，因为前者基于混合气的冷却时间，而后者基于热气的冷却时间。我们的模拟与混合气体的冷却时间符合阈值。我们认为，辐射云的模拟应运行足够长的时间，以允许由于混合气的冷却而导致致密气体的延迟生长，但背景气体不会造成灾难性冷却。此外，模拟域应足够大，以使混合气体不会在边界中损失。虽然混合层大致相同，但在不同温度下气体的发射率与同等单相稳定冷却流量根本不同。
We revisit the problem of the growth of dense/cold gas in the cloud-crushing setup with radiative cooling. The relative motion between the dense cloud and the diffuse medium produces a turbulent boundary layer of mixed gas with a short cooling time. This mixed gas may explain the ubiquity of the range of absorption/emission lines observed in various sources such as the circumgalactic medium and galactic/stellar/AGN outflows. Recently Gronke & Oh showed that the efficient radiative cooling of the mixed gas can lead to the continuous growth of the dense cloud. They presented a threshold cloud size for the growth of dense gas which was contradicted by the more recent works of Li et al. & Sparre et al. These thresholds are qualitatively different as the former is based on the cooling time of the mixed gas whereas the latter is based on the cooling time of the hot gas. Our simulations agree with the threshold based on the cooling time of the mixed gas. We argue that the radiative cloud-crushing simulations should be run long enough to allow for the late-time growth of the dense gas due to cooling of the mixed gas but not so long that the background gas cools catastrophically. Moreover, the simulation domain should be large enough that the mixed gas is not lost through the boundaries. While the mixing layer is roughly isobaric, the emissivity of the gas at different temperatures is fundamentally different from an isobaric single-phase steady cooling flow.
