Galaxies' Gas Loss In Cluster Environments: A Hydrodynamic Simulation Study.pdf

The study, titled "Gas Loss in Simulated Galaxies as They Fall into Clusters" (Cen et al., 2014), investigates how galaxies lose their cold gas when migrating from the field to high-density regions of galaxy clusters. Using high-resolution cosmological hydrodynamic galaxy formation simulations, researchers found:

Constant Gas-Rich Fraction at Large Distances: Beyond three cluster virial radii, the fraction of gas-rich galaxies remains constant, representing the field population.

Rapid Gas Loss Near Cluster Center: Within three cluster-centric radii, the fraction of gas-rich galaxies decreases steadily, reaching less than 10% near the cluster center.

Early Impact on Gas Content: Galaxies start experiencing the impact of the cluster environment on their gas content well beyond the cluster virial radius. Most gas-rich galaxies at the cluster virial radius are falling in for the first time at nearly radial orbits.

Minimal Gas-Rich Outward Movers: Almost no galaxy moving outward at the cluster virial radius is gas-rich (with a gas to baryon ratio greater than 1%). This suggests that galaxies lose their cold gas within a single radial round-trip upon falling into a cluster.

Key Implications:

The findings highlight:

The significant role of ram-pressure stripping in removing cold gas from galaxies as they enter clusters, consistent with previous observations.
The importance of the local density and orbital trajectories of galaxies in determining their evolution and gas loss.
* The potential for galaxy morphology and star formation rates to be strongly influenced by environmental factors even before galaxies reach the cluster core.