Dark energy and the structure of the Coma cluster of galaxies

Abstract

Context. We consider the Coma cluster of galaxies as a gravitationally bound physical system embedded in the perfectly uniform static dark energy background as implied by ΛCDM cosmology. Aims. We ask if the density of dark energy is high enough to affect the structure of a large and rich cluster of galaxies. Methods. We base our work on recent observational data on the Coma cluster, and apply our theory of local dynamical effects of dark energy, including the zero-gravity radius R ZG of the local force field as the key parameter. Results. 1) Three masses are defined that characterize the structure of a regular cluster: the matter mass M M , the dark-energy effective mass M DE (<0), and the gravitating mass M G (=M M + M DE ). 2) A new matter-density profile is suggested that reproduces the observational data well for the Coma cluster in the radius range from 1.4 Mpc to 14 Mpc and takes the dark energy background into account. 3) Using this profile, we calculate upper limits for the total size of the Coma cluster, R ≤ R ZG ≈ 20 Mpc, and its total matter mass,15 M . Conclusions. The dark energy antigravity affects the structure of the Coma cluster strongly at large radii R > ∼ 14 Mpc and should be considered when its total mass is derived.

Galaxy clusters in presence of dark energy: a kinetic approach

“…Qualitatively, the truncated Maxwellian distribution considered here is similar to the non-singular density distribution suggested by Chernin et al (2013). It may be used for a more detailed study of the density and velocity distribution on the periphery of rich clusters, where the influence of DE is significant, and their comparison with observations.…”

“…Then we described the density distribution inside galaxy clusters by several phenomenological functions, some of which follow from numerical simulations (see Chernin et al 2013). Qualitatively, the truncated Maxwellian distribution considered here is similar to the non-singular density distribution suggested by Chernin et al (2013).…”

Outer parts of large galactic clusters in the presence of dark energy

“…It is clear that the presence of DE tends to help the outflow of the hot gas from the gravitating object, as well as to the escape of rapidly moving galaxies [24]. Here we have obtained the solution for outflow in presence of DE, which generalize the well-known solution for the polytropic solar (stellar) wind.…”

“…In particular, it is necessary to check, when the cluster may exist in the equilibrium state, at present values of DE density, and the densities of matter, consisting of the baryonic, and dark matter (BM and DM). This problem was investigated in papers of Bisnovatyi-Kogan and Chernin [23] and Chernin et al [24], where the structure of galaxy clusters halo in Virgo and Coma were analyzed. It was obtained that the key physical parameters of the dark mater halos in clusters are determined by dark energy:…”

“…where the mass of Virgo cluster was estimated as radius are estimated as [24] R max = R ZG = 20 Mpc,…”