Comparison of source detection procedures for XMM-Newton images^*

CEA/DSM/DAPNIA Service d'Astrophysique, 91191 Gif-sur-Yvette, France

Corresponding author: I. Valtchanov, ivaltchanov@cea.fr

Received: 31 October 2000
Accepted: 8 February 2001

Abstract

Procedures based on current methods to detect sources in X-ray images are applied to simulated XMM-Newton images. All significant instrumental effects are taken into account, and two kinds of sources are considered -unresolved sources represented by the telescope PSF and extended ones represented by a β-profile model. Different sets of test cases with controlled and realistic input configurations are constructed in order to analyze the influence of confusion on the source analysis and also to choose the best methods and strategies to resolve the difficulties. In the general case of point-like and extended objects the mixed approach of multiresolution (wavelet) filtering and subsequent detection by SExtractor gives the best results. In ideal cases of isolated sources, flux errors are within 15-20% . The maximum likelihood technique outperforms the others for point-like sources when the PSF model used in the fit is the same as in the images. However, the number of spurious detections is quite large. The classification using the half-light radius and SExtractor stellarity index is successful in more than 98% of the cases. This suggests that average luminosity clusters of galaxies ( erg/s) can be detected at redshifts greater than 1.5 for moderate exposure times in the energy band below 5 keV, provided that there is no confusion or blending by nearby sources. We find also that with the best current available packages, confusion and completeness problems start to appear at fluxes around 6 10^-16 erg/s/cm² in [0.5-2] keV band for XMM-Newton deep surveys.