A search for protoclusters at z=3.3.

Abstract

The Very Large Array was used to image a single field in a set of adjacent frequency bands around 333.0 MHz in an attempt to detect 21 cm emission from large scale H I inhomogeneities at a redshift of z = 3.3. Following the subtraction of continuum radio sources, the absence of any spectral signals apart from that expected due to the system thermal noise has been used to derive constraints on the evolutionary scenario leading to the formation of the present day clusters of galaxies. The observations rule out the existence of H I protoclusters at z = 3.3 with masses of 3.5 x 10 to the 14th solar masses in H I gas and space density exceeding (74 Mpc) exp -3. This indicates that the present day rich clusters of galaxies either formed as gaseous protocluster condensates prior to z = 3.3 or else they formed through the clustering of their constituent galaxies.