Distance and mass of the M104 (Sombrero) group

TL;DR

This study estimates the dark matter mass of the M 104 galaxy group using distances and velocities of nearby galaxies, revealing a high mass-to-luminosity ratio indicative of substantial dark matter presence.

Contribution

The paper provides new distance measurements for dwarf galaxies near M 104 and derives its total mass and dark matter content using these data.

Findings

Total mass of M 104 is approximately 1.55 x 10^13 solar masses.

Mass-to-luminosity ratio of M 104 is about 65 solar units.

Dwarf galaxies are confirmed as satellites of M 104.

Abstract

Distances and radial velocities of galaxies in the vicinity of the luminous early-type galaxy M 104 (Sombrero) are used to derive its dark matter mass. Two dwarf galaxies: UGCA 307 and KKSG 30 situated near M 104 were observed with the Advanced Camera for Surveys on the Hubble Space Telescope. The distances $9.03^{+0.84}_{-0.51}$ Mpc (UGCA 307) and $9.72^{+0.44}_{-0.41}$ Mpc (KKSG 30) were determined using the tip of the red giant branch method. These distances are consistent with the dwarf galaxies being satellites of Sombrero. Using radial velocities and projected separations of UGCA 307, KKSG 30, and a third galaxy with an accurate distance (KKSG 29), as well as 12 other assumed companions with less accurate distances, the total mass of M 104 is estimated to be $(1.55\pm0.49) 10^{13} M_{\odot}$. At the K-band luminosity of the Sombrero galaxy of $2.4 10^{11} L_{\odot}$, its total mass-to-luminosity ratio is $M_T/L_K = (65\pm20)M_{\odot}/L_{\odot}$, which is about three times higher than that of luminous bulgeless galaxies.