Influence of baryonic physics on the merger time-scale of galaxies in
  N-body/hydrodynamical simulations
  Following our previous work(Jiang et al.(2008)), in which we studied the
merger time-scale of galaxies in a high-resolution cosmological hydro/N-body
simulation, we investigate the potential influence of uncertainties in the
numerical implementation of baryonic physics on the merger time-scale. The
simulation used in the previous work suffers from the overcooling problem which
causes the central galaxies of large halos too massive. This may result in a
shortened merger time-scale compared to that in the real universe. We run a
similar simulation, but the stellar mass is significantly reduced to model
another extreme case of low stellar mass. Our result shows that the merger
time-scale is little affected by the star formation recipes, except for the
satellites in nearly radial orbits which show a 22 percent higher time-scale in
the lower stellar mass case. Since the radial orbits only account for a small
part of the satellites' orbits, the fitting formula in Jiang et al.(2008) is
still applicable to a reasonable accuracy, nearly immune to the uncertainty in
the baryonic physics.
