Gas Loss in Simulated Galaxies as They Fall into Clusters
  We use high-resolution cosmological hydrodynamic galaxy formation simulations to gain insights on how galaxies lose their cold gas at low redshift as they migrate from the field to the high density regions of clusters of galaxies. We find that beyond three cluster virial radii, the fraction of gas-rich galaxies is constant, representing the field. Within three cluster-centric radii, the fraction of gas-rich galaxies declines steadily with decreasing radius, reaching $\mathbf{<10%}$ near the cluster center. Our results suggest that galaxies start to feel the impact of the cluster environment on their gas content well beyond the cluster virial radius. We show that almost all gas-rich galaxies at the cluster virial radius are falling in for the first time at nearly radial orbits. Furthermore, we find that almost no galaxy moving outward at the cluster virial radius is gas-rich (with gas to baryon ratio greater than $\mathbf{1%}$). These results suggest that galaxies that fall into clusters lose their cold gas within a single radial round-trip. 
Renyue Cen, Ana R. Pop and Neta A. Bahcall (Princeton University   Observatory)
astro-ph.GA