The seminar will be held in a mixed mode

1) Speaker: A.N. Baushev (JINR, Dubna)

Title: “Exact analytical solutions for the Hubble stream velocity field near a galaxy cluster and for the void central density”

Abstract: We present exact analytical solutions for two important practical tasks. We find the central density of a void for an arbitrary shape of the initial perturbation and show that the central density is solely determined by the amplitude of the perturbation. Our results suggest that N-body simulations somewhat overestimate the emptiness of voids: the majority of them should have the central underdensity delta_c > -73%, and there should be almost no voids with delta_c < -88%.

The gravitational field of a massive object (for instance, of a galaxy group or cluster) disturbs the Hubble stream, decreasing its speed. Dependence v(r) of the radial velocity of the stream can be directly observed and may provide valuable information about the cluster properties. We offer an exact analytical relationship v(r) for a spherically-symmetric system.

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