The Brera Multiscale WaveletROSATHRI Source Catalog. II. Application to the HRI and First Results

The wavelet detection algorithm (WDA) described in the accompanying paper by Lazzati et al. is suited to a fast and efficient analysis of images taken with the High-Resolution Imager (HRI) instrument on board the ROSAT satellite. An extensive testing is carried out on the detection pipeline: HRI fields with different exposure times are simulated and analyzed in the same fashion as the real data. Positions are recovered with errors of a few arcseconds, whereas fluxes are within a factor of 2 from their input values in more than 90% of the cases in the deepest images. Unlike the "sliding-box" detection algorithms, the WDA also provides a reliable description of the source extension, allowing for a complete search of, e.g., supernova remnants or clusters of galaxies in the HRI fields. A completeness analysis on simulated fields shows that for the deepest exposures considered (~120 ks) a limiting flux of ~3 × 10 -15 ergs s -1 cm -2 can be reached over the entire field of view. We test the algorithm on real HRI fields selected for their crowding and/or the presence of extended or bright sources (e.g., clusters of galaxies and stars, supernova remnants). We show that our algorithm compares favorably with other X-ray detection algorithms, such as XIMAGE and EXSAS. Analysis with the WDA of the large set of HRI data will allow us to survey ~400 deg 2 down to a limiting flux of ~10 -13 ergs s -1 cm -2 , and ~0.3 deg 2 down to ~3 × 10 -15 ergs s -1 cm -2 . A complete catalog will result from our analysis, consisting of the Brera Multiscale Wavelet Bright Source Catalog (BMW-BSC), with sources detected with a significance of ≳4.5 σ, and the Faint Source Catalog (BMW-FSC), with sources at ≳3.5 σ. A conservative estimate based on the extragalactic log N -log S indicates that at least 16,000 sources will be revealed in the complete analysis of the entire HRI data set.