Sub-Arcminute anisotropies in the CMBR, including a possible S--Z signal from a cluster

R. B. Partridge

Haverford College

Abstract:

VLA observations at 8.4 GHz of a field within one of the Hubble MDS regions have allowed us to set upper limits on fluctuations in the CMBR on angular scales from

down to

. The data from this field, combined with a somewhat shorter integration on another field, establishes the following limits on

confidence level: 12.8, 4.8 and

at angular scales of

and

, respectively.

Near the center of this field, an isolated, negative feature was found. It was with a peak central amplitude of 250 . We interpret it as the Sunyaev--Zel'dovich signal from a high redshift cluster. Interestingly, within about of this decrement, lie two radio-quiet quasars both at . If the signal is from a cluster of galaxies, failure to observe the source in a deep ROSAT exposure suggests its redshift must exceed 1.5. There is no optical evidence from the MDS survey frames for a cluster in the vicinity of the microwave decrement, again suggesting high redshift.

This detection is very similar to one to be discussed at this conference by the Cambridge group; I suggest we refer to these objects as ``Black Clouds'' to honor Sir Fred Hoyle.

PPEUC Proceedings
Fri Jul 25 11:59:20 BST 1997