We collected data on radial velocities and distances of galaxies to elucidate structure and kinematics of the filament attached to the Virgo cluster from south .
In the region RA = [ 12.5 - 13.5 ] ^ { h } , Dec = [ -20 - 0 ] ^ { \circ } there are 171 galaxies with radial velocities V _ { LG } < 2000 km s ^ { -1 } , and 98 of them have distance estimates .
This galaxy cloud , called as “ Virgo Southern Extension ” , is situated just on the edge of the Virgo “ zero-velocity surface ” .
The mean distance to Virgo SEx , 17 \pm 2 Mpc , and the average radial velocity , 1172 \pm 23 km s ^ { -1 } , are very close to the Virgo cluster ones .
In Supergalactic coordinates the Virgo SEx dimensions are 15 \times 7 \times 2 Mpc , where the major axis is directed along the line of sight , the second-major axis looks towards the Virgo core and the minor one is perpendicular to the Supergalactic plane .
This flattened cloud consists of a dozen virialized groups with the total K -band luminosity of 1.7 \cdot 10 ^ { 12 } L _ { \odot } and the total virial mass of 6.3 \cdot 10 ^ { 13 } M _ { \odot } , having a typical dark matter-to- stellar matter ratio of 37 .
The Hubble diagram for Virgo SEx galaxies exhibits a tendency of Z -shape wave with a velocity amplitude of \sim 250 km s ^ { -1 } that may be caused by a mass overdensity of \sim 6 \cdot 10 ^ { 13 } M _ { \odot } , and in order of magnitude agrees with the sum of virial masses of the groups .