Comparing galactic satellite properties in hydrodynamical and N-body simulations

Abstract

In this work, we examine the different properties of galactic satellites in hydrodynamical and pure dark matter simulations. We use three pairs of simulations (collisional and collision-less) starting from identical initial conditions. We concentrate our analysis on pairs of satellites in the hydro and Nbody runs that form from the same Lagrangian region. We look at the radial positions, mass loss as a function of time and orbital parameters of these "twin" satellites. We confirm an overall higher radial density of satellites in the hydrodynamical runs, but find that trends in the mass loss and radial position of these satellites in the inner and outer region of the parent halo differ from the pure dark matter case. In the outskirts of the halo (~70% of the virial radius) satellites experience a stronger mass loss and higher dynamical friction in pure dark matter runs. The situation is reversed in the central region of the halo, where hydrodynamical satellites have smaller apocenter distances and suffer higher mass stripping. We partially ascribe this bimodal behaviour to the delayed infall time for hydro satellites, which on average cross the virial radius of the parent halo 0.7 Gyrs after their dark matter twins. Finally, we briefly discuss the implications of the different set of satellite orbital parameters and mass loss rates in hydrodynamical simulations within the context of thin discs heating and destruction.