The effect of hydrodynamics alone on the subhalo population in a
  $\Lambda$CDM rich cluster sized dark matter halo
  We perform a set of non-radiative hydro-dynamical (NHD) simulations of a rich
cluster sized dark matter halo from the Phoenix project with 3 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
($M_{sub} > 2.5 \times 10^9h^{-1}M_{\odot}$, or $V_{max} > 70 kms^{-1}$) 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
$10^{10} h^{-1}M_{\odot}$ 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.
