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Activity Number: 485
Type: Contributed
Date/Time: Wednesday, August 7, 2013 : 8:30 AM to 10:20 AM
Sponsor: Section on Physical and Engineering Sciences
Abstract - #309660
Title: Overlapping Astronomical Sources
Author(s): David Jones*+ and Vinay Kashyap and David van Dyk
Companies: Harvard University and Harvard-Smithsonian Center for Astrophysics and Imperial College London
Keywords: astrostatistics ; detection ; spectral ; mixture ; overlapping ; RJMCMC
Abstract:

In astronomical observations, it is often the case that sources are situated close enough together that they cannot be fully resolved instrumentally and it is of interest to infer the number of individual sources, their locations, and their respective intensities. The resolution of the detector is characterized by the point spread function (PSF) which describes the spatial distribution of observed photons from a point source. Convolving a number of sources with the PSF results in a finite mixture model. We further incorporate spectral models, background contamination, and a latent Poisson process for the number and positions of the sources. We fit the resulting multilevel model with RJMCMC (Richardson and Green 1997) to separate the sources and obtain posterior distributions for the number of sources and their individual parameters. This overall approach has the benefit of being able to incorporate further complexities such as non-uniform background and asymmetric PSFs. Overfitting problems are avoided because knowledge of the PSF means the spread of the mixture components is determined making the inference relatively insensitive to the choice of prior on the number of sources.


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