Simulations and observations have found long tails in ‘jellyfish galaxies’, which are commonly thought to originate from ram-pressure stripped gas of the interstellar medium (ISM) in the immediate galactic wake. At larger distances from the galaxy, the long tails have been claimed to form in situ, owing to thermal instability and fast radiative cooling of mixed ISM and intracluster medium (ICM). In this paper, we use magnetohydrodynamical wind tunnel simulations of a galaxy with the AREPO code to study the origin of gas in the tails of jellyfish galaxies. To this end, we modelled the galaxy orbit in a cluster by accounting for a time-varying galaxy velocity, ICM density, and the turbulent magnetic field. By tracking gas flows between the ISM, the circumgalactic medium (CGM), and the ICM, we find – contrary to popular opinion – that the majority of the gas in the tail originates in the CGM. Prior to the central passage of the jellyfish galaxy in the cluster, the CGM is directly transported to the clumpy jellyfish tail that has been shattered into small cloudlets. After the central cluster passage, gas in the tail originates both from the initial ISM and the CGM, but that from the latter is accreted onto the galactic ISM before being ram-pressure stripped to form filamentary tentacles in the tail. Our simulation shows a declining gas metallicity in the tail as a function of downstream distance from the galaxy. We conclude that the CGM plays an important role in shaping the tails of jellyfish galaxies.

中文翻译：

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比较水母星系尾部气体的星际和银河系周围起源


模拟和观测在“水母星系”中发现了长尾巴，这通常被认为来自银河系尾流中星际介质 （ISM） 的冲压压力剥离气体。在距离星系较远的地方，由于混合ISM和星系团内介质（ICM）的热不稳定性和快速辐射冷却，长尾被认为是在原地形成的。在本文中，我们使用带有 AREPO 代码的星系的磁流体动力学风洞模拟来研究水母星系尾部气体的来源。为此，我们通过考虑时变星系速度、ICM 密度和湍流磁场来模拟星系团中的星系轨道。通过跟踪 ISM、银河系外介质 （CGM） 和 ICM 之间的气体流动，我们发现 - 与普遍的看法相反 - 尾部的大部分气体都来自 CGM。在星系团中水母星系的中心通道之前，CGM 被直接输送到已经破碎成小云状的团块状水母尾巴上。在中心星团通过后，尾部的气体来自初始 ISM 和 CGM，但来自后者的气体在被冲压压力剥离在尾部形成丝状触手之前被吸积到银河系的 ISM 上。我们的模拟显示，尾部的气体金属丰度随着与星系下游距离的函数而变化。我们得出结论，CGM 在塑造水母星系的尾巴方面起着重要作用。