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.
