Бисноватый-Коган Геннадий Семенович, гнс, отдел 64


Цикл из 2-х работ: Космологические объекты при наличии темной энергии



Galaxy clusters in presence of dark energy: a kinetic approach


M. Merafina, G. S. Bisnovatyi-Kogan, and M. Donnari, Astronomy & Astrophysics 568, A93 (2014)



Context. The external regions of galaxy clusters may be under strong influence of the dark energy, which was discovered by observations of supernovae Ia at redshift z < 1. The presence of the dark energy in the gravitational equilibrium equation, with the Einstein Λ term, balances the gravity, and extends the equilibrium configuration more in radius.

Aims. We investigate the features of the equilibrium configurations to analyse how the presence of the dark energy affects the density profiles and radial extension by specifying the conditions for which the gravitational equilibrium begins.

Methods. We derived the kinetic equation for an equilibrium configuration in presence of dark energy and solved the gravitational equilibrium equation by considering a Maxwell-Boltzmann distribution function with a cut-off in the framework of the Newtonian regime, because the observed velocities of galaxies inside a cluster are much lower than the velocity of light.

Results. The prevalence of dark energy effects on the gravity shows a wide region in the W0–ρΛ diagram where equilibrium solutions are not possible. In these particular conditions, the galaxies located in the external regions of a cluster can flow out, following the accelerating expansion of the Universe.



Galactic Cluster in the Presence of Dark Energy


G. S. Bisnovatyi-Kogan, Gravitation and Cosmology, 2014, Vol. 20, No. 3, pp. 157–164.


AbstractA solution for cosmological expansion in the presence of dark matter is presented, and observational results from which a conclusion on the present value of the cosmological constant is obtained, are discussed. A solution is obtained for hydrodynamic outflow of polytropic gas from a gravitating center, in the presence of uniform Dark Energy (DE). The antigravity of DE is enlightening the outflow and makes the outflow possible at smaller initial temperature at the same density. The main property of the wind in the presence of DE is its unlimited acceleration after passing the critical point. Applying this solution to winds from galaxy clusters, we suggest that a collision of a strongly accelerated wind with another galaxy cluster, or with another galactic cluster wind, could lead to the formation of highest energy cosmic rays.