Peculiar Motions in the Region of the Ursa Major Supercluster of Galaxies

TL;DR

This study analyzes the peculiar motions of galaxy clusters in the Ursa Major supercluster using SDSS data, finding minimal deviations from Hubble flow and suggesting the supercluster is gravitationally bound, with potential for more precise measurements.

Contribution

It provides the first detailed analysis of cluster peculiar velocities in the UMa supercluster using the fundamental plane method with SDSS data.

Findings

Peculiar velocities do not exceed measurement errors significantly.

The supercluster is likely gravitationally bound.

Current measurement accuracy limits confirmation of subsystem approaches.

Abstract

We have investigated the peculiar motions of clusters of galaxies in the Ursa Major (UMa) supercluster and its neighborhood. Based on SDSS (Sloan Digital Sky Survey) data, we have compiled a sample of early-type galaxies and used their fundamental plane to determine the cluster distances and peculiar velocities. The samples of early-type galaxies in the central regions (within R_200) of 12 UMa clusters of galaxies, in three main subsystems of the supercluster -- the filamentary structures connecting the clusters, and in nine clusters from the nearest UMa neighborhood have similar parameters. The fairly high overdensity (3 by the galaxy number and 15 by the cluster number) suggests that the supercluster as a whole is gravitationally bound, while no significant peculiar motions have been found: the peculiar velocities do not exceed the measurement errors by more than a factor of 1.5-2. The mean random peculiar velocities of clusters and the systematic deviations from the overall Hubble expansion in the supercluster are consistent with theoretical estimates. For the possible approach of the three UMa subsystems to be confirmed, the measurement accuracy must be increased by a factor of 2-3.