盘-日冕界面处气体冷却和吸积的效率
Efficiency of gas cooling and accretion at the disc-corona interface
摘要：
在恒星形成的星系中，恒星反馈对环星系介质有双重影响，既抑制又刺激气体吸积。气体吸积的触发可能是由盘物质以喷泉云的形式喷射到晕中以及与周围热日冕的相互作用引起的。事实上，在盘-日冕界面处，冷的/富含金属的盘气体（T <~ 10^4 K）和热的日冕气体（T >~ 10^6 K）之间的混合可以显著减少日冕部分的冷却时间，并产生其凝聚和吸积。我们通过秒差距尺度的流体动力学模拟研究了不同星系环境中喷泉云和日冕之间的相互作用，包括热传导的存在，这是影响气体凝结的关键机制。我们的模拟表明，日冕气体凝结强烈地依赖于星系环境，特别是它对于增加星系所在的晕的维里温度/质量的效率较低，并且对于维里质量大于10^13 Msun的物体完全无效。这一结果意味着，日冕气体在中低维里质量（Mvir <~ 3 x 10^12 Msun）的晕中迅速冷却，但从晚型到早型盘星系冷却日冕的能力降低，可能导致吸积关闭和大质量系统中恒星形成的淬灭。
英文摘要：
In star-forming galaxies, stellar feedback can have a dual effect on the circumgalactic medium both suppressing and stimulating gas accretion. The trigger of gas accretion can be caused by disc material ejected into the halo in the form of fountain clouds and by its interaction with the surrounding hot corona. Indeed, at the disc-corona interface, the mixing between the cold/metal-rich disc gas (T <~ 10^4 K) and the hot coronal gas (T >~ 10^6 K) can dramatically reduce the cooling time of a portion of the corona and produce its condensation and accretion. We studied the interaction between fountain clouds and corona in different galactic environments through parsec-scale hydrodynamical simulations, including the presence of thermal conduction, a key mechanism that influences gas condensation. Our simulations showed that the coronal gas condensation strongly depends on the galactic environment, in particular it is less efficient for increasing virial temperature/mass of the haloes where galaxies reside and it is fully ineffective for objects with virial masses larger than 10^13 Msun. This result implies that the coronal gas cools down quickly in haloes with low-intermediate virial mass (Mvir <~ 3 x 10^12 Msun) but the ability to cool the corona decreases going from late-type to early-type disc galaxies, potentially leading to the switching off of accretion and the quenching of star formation in massive systems.
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