On the rotation and clustering of galaxies

Abstract

The tidal torque theory for the origin of galactic rotation has been investigated using N-body computer simulations. The results show that this process is considerably less efficient than was previously thought, though consistent with recent observations of the rotation of giant elliptical galaxies. Spectroscopic observations of three elliptical galaxies along both major and minor axes are presented. Two galaxies were found to be slowly rotating, inconsistent with rotationally supported oblate spheroids. No convincing evidence for minor axis rotation was found. An investigation of the clustering of particles in Friedmann models of the Universe has been carried out using N-body simulations. The results of these computations have been analysed in terms of the two- and three- point correlation functions and various velocity statistics. It is found that the shapes of the two- and three-point functions are dependent upon the cosmological density parameter Ω, and that the shape of the two-point function is in rough agreement with simple analytic treatments based on the homogeneous spherical cluster model for the collapse of protoclusters. The effects of particle discreteness and two-body relaxation, which are particularly important in the N-body models are examined. The approach is compared to the detailed kinetic theory calculations of Davis and Peebles. The cosmological implications of the results are discussed. Other statistics, such as the multiplicity function are also considered.