EDP Sciences
Free access
Volume 408, Number 1, September II 2003
Page(s) 39 - 42
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20030949

A&A 408, 39-42 (2003)
DOI: 10.1051/0004-6361:20030949

The diffuse X-ray background

A. M. Soltan

Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland
(Received 13 May 2003 / Accepted 16 June 2003)

The deepest observations of the X-ray background approach the surface brightness of the truly diffuse component generated by Thomson scattering of cosmic X-ray photons. Available estimates of the electron density and the X-ray luminosity density of AGNs as a function of cosmological epoch are used to calculate the integral scattered X-ray background component. It is shown that the scattered component constitutes 1.0 - 1.7% of the total background, depending on the AGN cosmic evolution. Albeit this is a minute fragment of the total flux, it becomes a perceptible fraction of the still unresolved part of the background and should be taken into account in the future rigorous assessments of the X-ray background structure. This diffuse component at energies $\lse$ 1 keV sums up with the emission by WHIM to 3-4%. Consequently, one should expect that integrated counts of discrete sources account for just 96-97% for soft background and ~ 99% at higher energies.

Key words: X-rays: diffuse background

© ESO 2003