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

TL;DR

This study examines how uncertainties in baryonic physics modeling affect galaxy merger time-scales in simulations, finding minimal impact except for specific orbital configurations, thus supporting the robustness of existing merger time-scale formulas.

Contribution

It demonstrates that variations in baryonic physics modeling have limited effect on galaxy merger time-scales in simulations, validating previous fitting formulas.

Findings

Merger time-scales are largely unaffected by star formation recipe variations.

Radial orbit satellites show a 22% increase in merger time-scale with lower stellar mass.

Existing formulas remain accurate despite baryonic physics uncertainties.

Abstract

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.