An Analysis of X-ray Binary Populations Outside the Visible Extent of Nearby Galaxies

The X-ray point source population outside the visible extent of galaxies as defined by RC3 D25 has been assumed by the greater astronomical community to be dominated by the resolved AGN X-ray background. It is important to note however that this assumption was never rigorously tested though the analysis of observations from the Chandra X-ray Observatory, which has the spatial resolution and sensitivity required to suitably answer this question. Thus, the primary focus of this research is on studying the X-ray point source populations immediately outside the optical extent of each galaxy in a volume limited sample containing every galaxy within 15 Mpc observed by the Chandra X-ray Observatory from its launch until May, 2016. From this analysis it can be determined if there exists a population of X-ray binaries gravitationally associated with the host galaxy outside its visible extent. If such a population exists it may be a useful probe to study the minor merger interaction history of the host galaxy along with the X-ray occupation fraction of globular clusters. In addition, initial results from this research suggests that models based on ray traced simulations for estimating the point source detection error of Chandra underestimates the limiting flux of Chandra by approximately an order of magnitude. By fitting the direct observations rather than relying on detecting artificial raytraced sources an accurate empirical model for the limiting flux of Chandra can be constructed. With continued analysis of this sample of 66 galaxies, we are confident that these constraints on the X-ray extent of nearby galaxies will be applicable to the entire population of nearby galaxies.