1999/04/27 by Sergio Campana, Davide Lazzati, Maria Rosa Panzera +1 · 3 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/307789
6 pages, 11 PostScript figures, 1 gif figure, ApJ in press
arxiv created 1999/04/27 · openalex publication_date 1999/10/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
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.