Ram pressure stripping in a galaxy formation model. I. A novel numerical
  approach
  We develop a new numerical approach to describe the action of ram pressure
stripping (RPS) within a semi-analytic model of galaxy formation and evolution
which works in combination with non-radiative hydrodynamical simulations of
galaxy clusters. The new feature in our method is the use of the gas particles
to obtain the kinematical and thermodynamical properties of the intragroup and
intracluster medium (ICM). This allows a self-consistent estimation of the RPS
experienced by satellite galaxies. We find that the ram pressure (RP) in the
central regions of clusters increases approximately one order of magnitude
between z = 1 and 0, consistent with the increase in the density of the ICM.
The mean RP experienced by galaxies within the virial radius increases with
decreasing redshift. In clusters with virial masses M_vir ~10^15 h^-1 M_Sun,
over 50 per cent of satellite galaxies have experienced RP ~10^(-11) h^2 dyn
cm^-2 or higher for z <= 0.5. In smaller clusters (M_vir ~10^14 h^-1 M_Sun) the
mean RP are approximately one order of magnitude lower at all redshifts. RPS
has a strong effect on the cold gas content of galaxies for all cluster masses.
At z = 0, over 70 per cent of satellite galaxies within the virial radius are
completely depleted of cold gas. For the more massive clusters the fraction of
depleted galaxies is already established at z ~ 1, whereas for the smaller
clusters this fraction increases appreciably between z = 1 and 0. This
indicates that the rate at which the cold gas is stripped depends on the virial
mass of the host cluster. Compared to our new approach, the use of an analytic
profile to describe the ICM results in an overestimation of the RP larger than
50 per cent for z >= 0.5.
