Formation of Cold Filaments in Galaxy Clusters Linked to AGN Activity

Researchers Xiaodong Duan and Fulai Guo have utilized hydrodynamic simulations to explore the formation of cold filaments in galaxy clusters. Their study, titled "Cold Filaments Formed in Hot Wake Flows Uplifted by Active Galactic Nucleus Bubbles in Galaxy Clusters," demonstrates that these filaments can naturally condense from hot gaseous wake flows uplifted by jet-inflated active galactic nucleus (AGN) bubbles. The simulated filaments extend to tens of kiloparsecs from the cluster center and possess a mass range of 10^8 to 10^9 solar masses for a typical AGN outburst energy of 10^60 ergs. These filaments exhibit smooth velocity gradients and velocity dispersions of several hundred kilometers per second.

The study highlights that the properties of cold filaments are significantly influenced by the characteristics of AGN jets. Thermal-energy-dominated jets are more effective in producing long, massive cold filaments compared to kinetic-energy-dominated jets. Additionally, AGN jets with an early activation time, a low jet base, or very high power tend to overheat the cluster center, resulting in shorter cold filaments that take longer to condense.

These findings provide insights into the mechanisms behind the formation of cold filaments in galaxy clusters, which have been observed through multi-wavelength observations but whose formation processes were previously debated. Understanding these mechanisms is crucial for comprehending the dynamics and evolution of galaxy clusters.