A Baryonic Effect on the Merger Timescale of Galaxy Clusters
  Accurate estimation of the merger timescale of galaxy clusters is important
to understand the cluster merger process and further the formation and
evolution of the large-scale structure of the universe. In this paper, we
explore a baryonic effect on the merger timescale of galaxy clusters by using
hydrodynamical simulations. We find that the baryons play an important role in
accelerating the merger process. The merger timescale decreases with increasing
the gas fraction of galaxy clusters. For example, the merger timescale is
shortened by a factor of up to 3 for merging clusters with gas fractions 0.15,
compared with the timescale obtained with zero gas fractions. The baryonic
effect is significant for a wide range of merger parameters and especially more
significant for nearly head-on mergers and high merging velocities. The
baryonic effect on the merger timescale of galaxy clusters is expected to have
impacts on the structure formation in the universe, such as the cluster mass
function and massive substructures in galaxy clusters, and a bias of "no-gas"
may exist in the results obtained from the dark matter-only cosmological
simulations.
