Influence of baryonic physics on the merger timescale of galaxies in N-body/hydrodynamical simulations

In previous work, we studied the merger timescale of galaxies in a high-resolution cosmological hydro/N-body simulation. We now investigate the potential influence of uncertainties in the numerical implementation of baryonic physics on the merger timescale. The simulation used in the previous work was affected by the overcooling problem, which caused the central galaxies of large halos to be too massive. This might be responsible for producing a shorter merger timescale than that in the real universe. We perform a similar simulation, but in which the stellar mass is reduced significantly to model another extreme case of low stellar mass. Our result indicates that in this case the merger timescale is systematically higher than that we measured before. However, the difference in these two cases is only about 10%, except for satellites in nearly radial orbits where the difference is larger, reaching 23 percent. Since the two simulations correspond to both the low and high stellar mass limiting cases, and nearly radial orbits account for only a small part of the satellites' orbits, our results indicate that the fitting formula that we presented previously is applicable to good accuracy.