Infall of nearby galaxies into the Virgo cluster as traced with HST
  We measured the Tip of the Red Giant Branch distances to nine galaxies in the
direction to the Virgo cluster using the Advanced Camera for Surveys on the
Hubble Space Telescope. These distances put seven galaxies: GR 34, UGC 7512,
NGC 4517, IC 3583, NGC 4600, VCC 2037 and KDG 215 in front of the Virgo, and
two galaxies: IC 3023, KDG 177 likely inside the cluster. Distances and radial
velocities of the galaxies situated between us and the Virgo core clearly
exhibit the infall phenomenon toward the cluster. In the case of spherically
symmetric radial infall we estimate the radius of the "zero-velocity surface"
to be (7.2+-0.7) Mpc that yields the total mass of the Virgo cluster to be
(8.0+-2.3) X 10^{14} M_sun in good agreement with its virial mass estimates. We
conclude that the Virgo outskirts does not contain significant amounts of dark
matter beyond its virial radius.
