Multiwavelength observations indicate that the intracluster medium in some galaxy clusters contains cold filaments, while their formation mechanism remains debated. Using hydrodynamic simulations, we show that cold filaments could naturally condense out of the hot gaseous wake flows uplifted by jet-inflated active galactic nucleus (AGN) bubbles. Consistent with observations, the simulated filaments extend to tens of kiloparsecs from the cluster center, with a representative mass of 10⁸–10⁹ M _⊙ for a typical AGN outburst energy of 10⁶⁰ erg. They show smooth velocity gradients, stretching typically from inner inflows to outer outflows with velocity dispersions of several hundred kilometers per second. The properties of cold filaments are affected substantially by the jet properties. Compared to kinetic-energy-dominated jets, it is easier for thermal-energy-dominated jets to produce long cold filaments with large masses, as observed. AGN jets with an early turn-on time, a low jet base, or a very high power tend to overheat the cluster center and produce short cold filaments that take a relatively long time to condense out.

中文翻译：

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星系团中活跃星系核气泡抬升的热尾流中形成的冷丝


多波长观测表明，一些星系团的簇内介质含有冷丝，但其形成机制仍存在争议。通过流体动力学模拟，我们发现冷细丝可以从喷射膨胀的活动星系核（AGN）气泡抬升的热气态尾流中自然凝结出来。与观测结果一致，模拟的细丝从星团中心延伸到数十千秒差距，典型质量为 10 ⁸ –10 ⁹ M _⊙ ，典型 AGN 爆发能量为 10 ⁶⁰尔格。它们表现出平滑的速度梯度，通常从内部流入延伸到外部流出，速度分散为每秒数百公里。冷丝的性能很大程度上受喷射性能的影响。正如所观察到的，与动能主导的射流相比，热能主导的射流更容易产生具有大质量的长冷丝。开启时间较早、射流基础较低或功率非常高的活动星系核射流往往会使星团中心过热，并产生短冷细丝，需要相对较长的时间才能凝结出来。