Proceedings of the Particle Physics and Early Universe Conference (PPEUC).
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A search for X-ray emission towards the SZ cluster candidate in the direction of the quasar pair PC1643+4631

R. Kneissl

Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85748 Garching bei München, Germany


We report on a 16 ks X-ray observation with the ROSAT PSPC towards the center of a CMB decrement detected by Jones et al. (1997) in the direction of the quasar pair PC1643+4631 A & B. At the position of the decrement we find no evidence for emission by hot gas which could give rise to the Sunyaev-Zel'dovich effect. The lowest bolometric flux upper limit (99.7 % CL) from the observation is derived in the energy range 0.5--2.0 keV within a radius of . We investigate whether a gas halo could be causing the decrement and find, with conservative assumptions about the cosmology and gas parameters, a high redshift limit of (95 % CL), not far from the redshift of the quasar pair (). We conclude that the CMB decrement is not a typical galaxy cluster. Since this decrement is not the only one without clear indication for an associated galaxy cluster (Richards et al. (1997)), we suggest to explore also other explanations for the CMB decrement.

PPEUC Proceedings
Wed Jul 16 13:49:24 BST 1997