On the contribution of point sources to the Galactic ridge X-ray emission

Abstract

We analyzed deep Chandra observations of the Galactic plane region centered at / = 28.55°, b = -0.03° with the aim to obtain the best possible constraints on the contribution of weak point sources to the Galactic ridge X-ray emission (GRXE) in this region. We demonstrate that the vast majority of the detected sources are Galactic in origin and are probably cataclysmic variables and coronally active stars. We use the number-flux function of detected sources to constrain the luminosity function of Galactic X-ray sources in the range 1030-1032 erg s-1 and find good agreement with the luminosity function of sources in the Solar vicinity. The fraction of the total flux at energies 1-7 keV resolved into point sources at the current sensitivity level is ∼25%. Excluding the expected contribution of extragalactic sources, ∼19% of the GRXE is due to point Galactic sources with interstellar absorption corrected fluxes higher than 1.2 × 10 -15 erg s-1 cm-2 in the energy band 1-7 keV. © ESO 2007.