Cold Filaments Formed in Hot Wake Flows Uplifted by AGN Bubbles in Galaxy Clusters

Multi-wavelength 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 hot gaseous wake flows uplifted by the jet-inflated active galactic nucleus (AGN) bubbles. Consistent with observations, the simulated filaments extend to tens of kpc from the cluster center, with a representative mass of $\rm 10^{8}- 10^{9}\ M_{\odot}$ for a typical AGN outburst energy of $10^{60}~ \rm erg$. They show smooth velocity gradients, stretching typically from inner inflows to outer outflows with velocity dispersions of several hundred $\rm km\ s^{-1}$. The properties of cold filaments are affected substantially by jet properties. Compared to kinetic energy-dominated jets, thermal energy-dominated jets tend to produce longer cold filaments with higher masses. With the same jet energy, AGN jets with an earlier turn-on time, a lower jet base, or a higher power heat the cluster center more effectively, and produce shorter filaments at a much later epoch.
Comment: 14 pages, 9 figures