Map of the Galaxy in the 6.7 keV emission line

Abstract

We study the two dimensional surface brightness distribution of the Galactic X-ray background emission outside the central degree around Sgr A* in the 6.7 keV line as measured by the PCA spectrometer of the RXTE observatory. The use of the emission line instead of continuum (3-20 keV) radiation and application of time variability filtering to the long data set allows us to strongly suppress the contamination of the GRXE map by bright point sources. The surface brightness in the 6.7 keV line demonstrates very good correspondence with the near-infrared surface brightness over the whole Galaxy, supporting the notion that the GRXE consists mostly of integrated emission from weak Galactic X-ray sources. We find compatible linear correlations between near-infrared and 6.7 keV surface brightness for the bulge and disk of the Galaxy. This indicates that the populations of weak X-ray sources making up the GRXE in the disk and bulge are not significantly different.