Do clusters of galaxies rotate?

Abstract

It is shown that the number of members, $N_A$, and the linear radius of the Abell clusters at $z<0.18$ increase with redshift. The increase is caused by observational selection: the number of rich and large clusters is small in the nearby small volume of space, while poor and small clusters are not detected at high distances. Besides, the numbers of clusters with different ellipticities are about the same at all distances, though in the case of cosmological evolution the number of the more elliptical clusters increases with decrease of distance. It means that clusters do not evolve dynamically. The dependences of the X-ray emission detection rate and the temperature of the X-ray emission on redshift are consequences of the dependence of $N_A$ on redshift. The radial velocity dispersion of the less elliptical clusters is higher than that of the elongated ones. This shows that galaxies in a cluster move preferentially along the large axis of the cluster. The space density is not changing in the considered range of $z$. Movement of galaxies along the cluster elongation may be explained by rotation along the large axis of a cluster.