Intense look at Virgo Southern Extension

TL;DR

This study investigates the structure and kinematics of the Virgo Southern Extension, a galaxy filament near the Virgo cluster, revealing its dimensions, mass distribution, and dynamic behavior through radial velocity and distance data.

Contribution

It provides detailed measurements and analysis of the Virgo Southern Extension's structure, mass, and kinematics, enhancing understanding of galaxy filament properties near the Virgo cluster.

Findings

Virgo SEx is a flattened galaxy cloud with dimensions 15x7x2 Mpc.

The mean distance to Virgo SEx is 17±2 Mpc, close to Virgo cluster.

The velocity field shows a Z-shape wave indicating a mass overdensity of about 6×10^13 solar masses.

Abstract

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]deg there are 171 galaxies with radial velocities VLG < 2000 km/s, 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, 17pm2 Mpc, and the average radial velocity, 1172pm23 km/s, are very close to the Virgo cluster ones. In Supergalactic coordinates the Virgo SEx dimensions are 15x7x2 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 1.7cdot10^12 Lsol and the total virial mass of 6.3cdot10^13 Msol, 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 ~250 km/s that may be caused by a mass overdensity of ~6cdot10^13 Msol, and in order of magnitude agrees with the sum of virial masses of the groups.