Journal Article

A deep <i>ROSAT</i> PSPC observation towards the CMB decrement close to PC1643+4631 A & B: no cluster X-ray emission

Rüdiger Kneissl, Rashid A. Sunyaev and Simon D. M. White

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 297, issue 2, pages L29-L33
Published in print June 1998 | ISSN: 0035-8711
Published online June 1998 | e-ISSN: 1365-2966 | DOI:
A deep ROSAT PSPC observation towards the CMB decrement close to PC1643+4631 A & B: no cluster X-ray emission

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We report on a 16-ks observation with the ROSAT PSPC centred on the cosmic microwave background (CMB) decrement which Jones et al. report in the direction of the quasar pair PC1643+4631 A&B. We do not detect the X-ray emission which would be expected if the decrement were caused by Compton up-scattering of CMB photons by hot gas. Our upper limit on the X-ray flux (0.5-2.0 keV) within a circle of radius 1.5 arcmin is 1.0 × 10−14 erg cm−2 s−1 at 99.7 per cent significance. We investigate the requirements for a spherical body of hot gas to produce the decrement while remaining consistent with our data. With conservative assumptions we establish a lower redshift limit of 2.8 at 95 per cent confidence for a 10-keV isothermal object of any size. Even higher limits obtain for objects with temperatures between 0.2 and 10 keV. A discussion of our result shows that an explanation other than Comptonization by hot gas within a virialized, cluster-like object, appears to be needed.

Keywords: galaxies: clusters: general; quasars: individual: PC1643+4631 A, B; cosmic microwave background; X-rays: general

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Subjects: Astronomy and Astrophysics

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