Cross-correlation between the soft X-ray background and SZ Sky

¹ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
² Department of Astronomy, Beijing Normal University, Beijing 100875, PR China
³ California Institute of Technology, Mail Code 130-33, Pasadena, CA 91125, USA

Corresponding author: L.-M. Cheng, clm@class1.bao.ac.cn

Received: 24 March 2003
Accepted: 30 September 2003

Abstract

While both X-ray emission and Sunyaev-Zel'dovich (SZ) temperature fluctuations are generated by the warm-hot gas in dark matter halos, the two observables have different dependence on the underlying physical properties, including the gas distribution. A cross-correlation between the soft X-ray background (SXRB) and the SZ sky may allow an additional probe on the distribution of warm-hot gas at intermediate angular scales and redshifts complementing studies involving clustering within SXRB and SZ separately. Using a halo approach, we investigate this cross-correlation analytically. The two contributions are correlated mildly with a correlation coefficient of ~0.3, and this relatively low correlation presents a significant challenge for its detection. The correlation, at small angular scales, is affected by the presence of radiative cooling or preheating and provides a probe on the thermal history of the hot gas in dark halos. While the correlation remains undetectable with CMB data from the WMAP satellite and X-ray background data from existing catalogs, upcoming observations with CMB missions such as Planck, for the SZ side, and an improved X-ray map of the large scale structure, such as the one planned with DUET mission, may provide a first opportunity for a reliable detection of this cross-correlation.