An investigation of a supercluster of galaxies in Piscis Austrinis

Abstract

An examination of a IIIaJ plate taken on the United Kingdom Schmidt Telescope of Survey field 405 revealed a possible supercluster of clusters of galaxies. Three rich clusters could be seen grouped within one degree, and which appeared to be of similar distance. The project described in this thesis has investigated the supercluster hypothesis by determining relative (and less precisely, absolute) distances to the three component clusters. It is described how the photographic material was painstakingly reduced to relative magnitudes and colours, and how these values were calibrated using a stellar sequence photo-electrically observed using the 1m telescope at South African Astronomical Observatory. Radial velocities were determined by a process which maximises the amount of information derived from intrinsically low-precision objective prism material. It is found that the Supercluster has, within the errors, a line-of-sight dimension of twice its projected dimension; this suggests that in fact the clusters of galaxies are in as close proximity spatially as they are apparently. The distance derived to the supercluster is 550 Mpc, giving a projected diameter of 10Mpc, with a recession velocity of 47700 kms⁻¹ which Leads to a determination of Hubble's constant: H₀ = 87 ±20kms⁻¹ Mpc⁻¹ .