``Investigation of Two Reported Arcminute-Scale Microwave Decrements at 28.5 GHz''

Manuscript: Postscript, PDF


The Ryle telescope has been used at a frequency of 15 GHz, to detect a flux decrement in the direction of the quasar pair PC 1643+4631A, B. This signal was interpreted as the Sunyaev-Zeldovich effect (SZE) produced by a distant cluster of galaxies. In the course of an effort to measure cosmic microwave background (CMB) anisotropies with a deep pointing of the VLA at 8.4 GHz, a second group detected a similar, but smaller, decrement. They also proposed that this signal might be explained as the SZE signal produced by a distant galaxy cluster. We report observations with the Berkeley-Illinois-Maryland Association (BIMA) interferometer operating at 28.5 GHz, in which we find no evidence for a SZE signal in the direction of either of the proposed clusters. In the case of the Ryle detection, the BIMA data are inconsistent with the SZE model proposed to explain the observed decrement at greater than 99.99% confidence. Together with published X-ray and optical searches, these results make a compelling case against the interpretation of the Ryle decrement as being due to the SZE in a massive cluster of galaxies. For the smaller VLA source, the BIMA observations are not as constraining. The BIMA data are inconsistent with the proposed SZE model at greater than 90% confidence.