The effect of hydrodynamics alone on the subhalo population in a ΛCDM rich cluster sized dark matter halo

Abstract

We perform a set of non-radiative hydro-dynamical (NHD) simulations of a rich cluster sized dark matter halo from the Phoenix Project with three different numerical resolutions, to investigate the effect of hydrodynamics alone on the subhalo population in the halo. Compared to dark matter only (DMO) simulations of the same halo, subhaloes are less abundant for relatively massive subhaloes (M sub > 2.5 × 109 h −1 M ⊙, or V max > 70 km s−1) but more abundant for less massive subhaloes in the NHD simulations. This results in different shapes in the subhalo mass/V max function in two different sets of simulations. At given subhalo mass, the subhaloes less massive than 1010 h −1 M ⊙ have larger V max in the NHD than DMO simulations, while V max is similar for the subhaloes more massive than the mass value. This is mainly because the progenitors of present day low mass subhaloes have larger concentration parameters in the NHD than DMO simulations. The survival number fraction of the accreted low mass progenitors of the main halo at redshift 2 is about 50 percent higher in the NHD than DMO simulations.