The X-ray Point Source Population of Spiral and Star-forming Galaxies.
thesisposted on 2008-11-19, 10:59 authored by Roy E. Kilgard
In this thesis, I study a sample of 11 nearby “normal” spiral galaxies and one starburst galaxy with the Chandra X-ray Observatory and supporting ground-based telescopes, with particular emphasis on the characterisation of the discrete X-ray point source population. Emission from discrete point sources dominates the X-ray flux from spiral galaxies. This survey spans the Hubble sequence for spirals and, hence, a range in star formation, allowing insights into the X-ray source population of many diverse systems. The inclusion of M82, the prototypical starburst galaxy in the nearby universe, allows for comparison with a system at the extreme of star formation. Presented here is a detailed catalogue of the source population of these galaxies. For each source, I have derived fluxes, luminosities, X-ray colours, and variability properties. I have also searched for optical and radio counterparts. For the most luminous sources, detailed spectral and temporal analyses have been performed. For galaxies as a whole, I have examined X-ray point source luminosity functions and how these relate to star formation of those galaxies. I have also devised a strategy for initial classification of X-ray sources based upon their position within a colour-colour diagram. The luminosity function analysis has then been performed on each class of sources, showing 1) that the method of classification appears to be robust to the first order, and 2) that the old and young (i.e. low-mass X-ray binary and high-mass X-ray binary) populations can be segregated, providing insight into the star formation history of each individual galaxy. I have also studied the environments in which the sources fall within their host galaxies and what this can tell us about the nature of the sources. I have included a discussion of the enigmatic ultraluminous X-ray sources (ULXs), which may be candidates for intermediate mass (100-10,000 Mסּ) black holes.