EDP Sciences
Free access
Volume 495, Number 3, March I 2009
Page(s) 989 - 1003
Section Astronomical instrumentation
DOI http://dx.doi.org/10.1051/0004-6361:200811311
Published online 14 January 2009
A&A 495, 989-1003 (2009)
DOI: 10.1051/0004-6361:200811311

Maximum-likelihood detection of sources among Poissonian noise

I. M. Stewart

Jodrell Bank Centre for Astrophysics, University of Manchester, Oxford Road, Manchester M13 9PL, UK
    e-mail: Ian.Stewart-2@manchester.ac.uk

Received 7 November 2008 / Accepted 31 December 2008

A maximum likelihood (ML) technique for detecting compact sources in images of the X-ray sky is examined. Such images, in the relatively low exposure regime accessible to present X-ray observatories, exhibit Poissonian noise at background flux levels. A variety of source detection methods are compared via Monte Carlo, and the ML detection method is shown to compare favourably with the optimized-linear-filter (OLF) method when applied to a single image. Where detection proceeds in parallel on several images made in different energy bands, the ML method is shown to have some practical advantages which make it superior to the OLF method. Some criticisms of ML are discussed. Finally, a practical method of estimating the sensitivity of ML detection is presented, and is shown to be also applicable to sliding-box source detection.

Key words: methods: data analysis -- techniques: image processing -- X-rays: general

© ESO 2009