Cosmic flow around local massive galaxies
Special Astrophysical Observatory of the Russian Academy of Sciences Nizhnij Arkhyz, 369167 Karachay-Cherkessia, Russia
Received: 24 July 2017
Accepted: 19 September 2017
Aims. We use accurate data on distances and radial velocities of galaxies around the Local Group, as well as around 14 other massive nearby groups, to estimate their radius of the zero-velocity surface, R0, which separates any group against the global cosmic expansion.
Methods. Our R0 estimate was based on fitting the data to the velocity field expected from the spherical infall model, including effects of the cosmological constant. The reported uncertainties were derived by a Monte Carlo simulation.
Results. Testing various assumptions about a location of the group barycentre, we found the optimal estimates of the radius to be 0.91 ± 0.05 Mpc for the Local Group, and 0.93 ± 0.02 Mpc for a synthetic group stacked from 14 other groups in the Local Volume. Under the standard Planck model parameters, these quantities correspond to the total mass of the group ~ (1.6 ± 0.2) × 1012M⊙. Thus, we are faced with the paradoxical result that the total mass estimate on the scale of R0 ≈ (3−4)Rvir is only 60% of the virial mass estimate. Anyway, we conclude that wide outskirts of the nearby groups do not contain a large amount of hidden mass outside their virial radius.
Key words: galaxies: groups: general / galaxies: groups: individual: Local Group
© ESO, 2017
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.