X-ray Astronomy and the Analysis of X-ray Data

摘要

The Chandra X-ray Observatory, launched in 1999, contin-ues to return spectacular scientific results thanks to its combination ofhigh spatial and spectral resolution. I will discuss a selection of theseresults, and draw attention to the specific data analysis challenges posedby X-ray observatories in general, leading to the identification of the spa-tial distribution of elements in supernova remnants, the discovery of X-rayjets in galactic and extragalactic objects, the resolution of the X-ray back-ground into faint sources, and the analysis of X-ray spectra of individualsources in external galaxies. The X-ray event list paradigm provides acompact representation of a sparse multidimensional dataset, support-ing time- and energy-resolved hundred-megapixel images. In contrast tothe case of HST and ground-based telescopes, the pointing of X-ray tele-scopes, while known accurately after the fact, is not kept constant duringthe observation. Sharp X-ray images are reconstructed from a ditheredpicture using star tracker data. The imaging point spread function andspectral energy response vary greatly across the field of view and mustbe carefully calibrated. For X-ray CCD data, the line spread functionis broad and multi-peaked, driving us to forward-fitting solutions. Forhigh resolution grating data, order separation is a challenge. Finally,in all X-ray data the low count rate and the ubiquitous cosmic X-raybackground require careful statistical attention. Despite these complexi-ties, the standard data analysis packages like CIAO, HEASOFT and SASare mature enough to allow non-specialist users to reliably extract highquality science from X-ray observations.