Abstract : Deproject 3-d cluster properties from 2-d data
Category : Recommended Active
Homepage : http://cxc.harvard.edu/contrib/deproject/
Deproject is a CIAO Sherpa extension package to facilitate deprojection of two-dimensional annular X-ray spectra to recover the three-dimensional source properties. For typical thermal models this would include the radial temperature and density profiles. This basic method has been used extensively for X-ray cluster analysis and is the basis for the XSPEC model projct. The deproject module brings this functionality to Sherpa as a Python module that is straightforward to use and understand.
The deproject module uses specstack to allow for manipulation of a stack of related input datasets and their models. Most of the functions resemble ordinary Sherpa commands (e.g. set_par, set_source, ignore) but operate on a stack of spectra.
The basic physical assumption of deproject is that the extended source emissivity is constant and optically thin within spherical shells whose radii correspond to the annuli used to extract the specta. Given this assumption one constructs a model for each annular spectrum that is a linear volume-weighted combination of shell models. The geometry is illustrated in the figure below (which would be rotated about the line to the observer in three-dimensions):