  We use a large suite of carefully controlled full hydrodynamic simulations to
study the ram pressure stripping of the hot gaseous halos of galaxies as they
fall into massive groups and clusters. The sensitivity of the results to the
orbit, total galaxy mass, and galaxy structural properties is explored. For
typical structural and orbital parameters, we find that ~30% of the initial hot
galactic halo gas can remain in place after 10 Gyr. We propose a physically
simple analytic model that describes the stripping seen in the simulations
remarkably well. The model is analogous to the original formulation of Gunn &
Gott (1972), except that it is appropriate for the case of a spherical (hot)
gas distribution (as opposed to a face-on cold disk) and takes into account
that stripping is not instantaneous but occurs on a characteristic timescale.
The model reproduces the results of the simulations to within approximately 10%
at almost all times for all the orbits, mass ratios, and galaxy structural
properties we have explored. The one exception involves unlikely systems where
the orbit of the galaxy is highly non-radial and its mass exceeds about 10% of
the group or cluster into which it is falling (in which case the model
under-predicts the stripping following pericentric passage). The proposed model
has several interesting applications, including modelling the ram pressure
stripping of both observed and cosmologically-simulated galaxies and as a way
to improve current semi-analytic models of galaxy formation. One immediate
consequence is that the colours and morphologies of satellite galaxies in
groups and clusters will differ significantly from those predicted with the
standard assumption of complete stripping of the hot coronae.
