  The origin of the deficiency in neutral Hydrogen of 13 spiral galaxies lying
in the outskirts of the Virgo cluster is reassessed. If these galaxies have
passed through the core of the cluster, their interstellar gas should have been
lost through ram pressure stripping by the hot X-ray emitting gas of the
cluster. We analyze the positions of these HI-deficient and other spiral
galaxies in velocity-distance plots, in which we include our compilation of
velocity-distance data on 61 elliptical galaxies, and compare with simulated
velocity-distance diagrams obtained from cosmological N-body simulations. We
find that ~20% relative Tully-Fisher distance errors are consistent with the
great majority of the spirals, except for a small number of objects, whose
positions in the velocity-distance diagram suggest grossly incorrect distances,
which implies that the Tully-Fisher error distribution function has
non-gaussian wings. Moreover, we find that the distance errors may lead to an
incorrect fitting of the Tolman-Bondi solution that can generate significant
errors in the distance and especially the mass estimates of the cluster. We
suggest 4 possibilities for the outlying HI-deficient spirals (in decreasing
frequency): 1) they have large relative distance errors and are in fact close
enough (at distances between 12.7 and 20.9 Mpc from us) to the cluster to have
passed through its core and seen their gas removed by ram pressure stripping;
2) their gas is converted to stars by tidal interactions with other galaxies;
3) their gas is heated during recent mergers with smaller galaxies; and 4) they
are in reality not HI-deficient (e.g. S0/a's misclassified as Sa's).
