Ram Pressure Stripping Made Easy: An Analytical Approach
  The removal of gas by ram pressure stripping of galaxies is treated by a
purely kinematic description. The solution has two asymptotic limits: if the
duration of the ram pressure pulse exceeds the period of vertical oscillations
perpendicular to the galactic plane, the commonly used quasi-static criterion
of Gunn & Gott is obtained which uses the maximum ram pressure that the galaxy
has experienced along its orbit. For shorter pulses the outcome depends on the
time-integrated ram pressure. This parameter pair fully describes the gas mass
fraction that is stripped from a given galaxy. This approach closely reproduces
results from SPH simulations. We show that typical galaxies follow a very tight
relation in this parameter space corresponding to a pressure pulse length of
about 300 Myr. Thus, the Gunn & Gott criterion provides a good description for
galaxies in larger clusters. Applying the analytic description to a sample of
232 Virgo galaxies from the GoldMine database, we show that the ICM provides
indeed the ram pressures needed to explain the deficiencies. We also can
distinguish current and past strippers, including objects whose stripping state
was unknown.
