Small-scale fluctuations of the soft X-ray background
Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland
2 MPI für extraterrestrische Physik, Giessenbachstr., 85748 Garching, Germany e-mail: firstname.lastname@example.org (MJF); email@example.com (JT)
Corresponding author: A. Soltan, firstname.lastname@example.org
Accepted: 6 September 2001
We report the detection of the X-ray background fluctuations at small angular scales. ROSAT PSPC archive pointed observations are used to measure the autocorrelation function (ACF) of the background at scales of -. The pointings have been selected from an area apparently free from galactic contamination and the ACF signal is generated mostly by the extragalactic component of the XRB. At separations below ~ known X-ray clusters of galaxies become a substantial source of the background fluctuations. Assuming a power law, the ACF for all the data has a slope of ~, but is substantially flatter (with slope of ~) when pointings containing bright clusters are removed. Flattening of the ACF at small separations could indicate existence of a hot, nonuniformly distributed gas accumulating in wells of gravitational potential. At separations - where the ACF estimates based on the ROSAT pointings and All-Sky Survey are available, both data sets give consistent results.
Key words: X-rays: general / diffuse radiation
© ESO, 2001