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

We analyzed deep Chandra observations of the Galactic plane region centered at l = 28.55 degrees, b = - 0.03 degrees 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 10(30)-10(32) 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 similar to 25%. Excluding the expected contribution of extragalactic sources, similar to 19% of the GRXE is due to point Galactic sources with interstellar absorption corrected fluxes higher than 1.2 x 10(-15) erg s(-1) cm(-2) in the energy band 1-7 keV.