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 \pm 0.7 ) Mpc that yields the total mass of the Virgo cluster to be ( 8.0 \pm 2.3 ) \times 10 ^ { 14 } M _ { \odot } 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 .