The Brera Multi-scale Wavelet (BMW) ROSAT HRI source catalog. I: the algorithm

We present a new detection algorithm based on the wavelet transform for the analysis of high energy astronomical images. The wavelet transform, due to its multi-scale structure, is suited for the optimal detection of point-like as well as extended sources, regardless of any loss of resolution with the off-axis angle. Sources are detected as significant enhancements in the wavelet space, after the subtraction of the non-flat components of the background. Detection thresholds are computed through Monte Carlo simulations in order to establish the expected number of spurious sources per field. The source characterization is performed through a multi-source fitting in the wavelet space. The procedure is designed to correctly deal with very crowded fields, allowing for the simultaneous characterization of nearby sources. To obtain a fast and reliable estimate of the source parameters and related errors, we apply a novel decimation technique which, taking into account the correlation properties of the wavelet transform, extracts a subset of almost independent coefficients. We test the performance of this algorithm on synthetic fields, analyzing with particular care the characterization of sources in poor background situations, where the assumption of Gaussian statistics does not hold. For these cases, where standard wavelet algorithms generally provide underestimated errors, we infer errors through a procedure which relies on robust basic statistics. Our algorithm is well suited for the analysis of images taken with the new generation of X-ray instruments equipped with CCD technology which will produce images with very low background and/or high source density.Comment: 8 pages, 6 figures, ApJ in pres

The Brera Multi-scale Wavelet (BMW) ROSAT HRI 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 made suited for 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 analysed in the same fashion as the real data. Positions are recovered with few arcsecond errors, whereas fluxes are within a factor of two from their input values in more than 90% of the cases in the deepest images. At variance with the ``sliding-box'' detection algorithms, the WDA provides also a reliable description of the source extension, allowing for a complete search of e.g. supernova remnant or cluster 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 \~3x10^{-15} erg/cm2/s can be reached over the entire field of view. We test the algorithm on real HRI fields selected for their crowding and/or presence of extended or bright sources (e.g. cluster of galaxies and of stars, supernova remnants). We show that our algorithm compares favorably with other X-ray detection algorithms such as XIMAGE and EXSAS. A complete catalog will result from our analysis: it will consist of the Brera Multi-scale Wavelet Bright Source Catalog (BMW-BSC) with sources detected with a significance >4.5 sigma and of the Faint Source Catalog (BMW-FSC) with sources at >3.5 sigma. A conservative estimate based on the extragalactic log(N)-log(S) indicates that at least 16000 sources will be revealed in the complete analysis of the whole HRI dataset.Comment: 6 pages, 11 PostScript figures, 1 gif figure, ApJ in pres

SpaceInn Work Package 3.3 Accompanying report on the deliverables D3.9 due for June 30: simultaneous spectroscopy and photometry

The ground-based CoRoT complementary archive (Work Package 3.3) contains 7103 spectra of the 261 stars observed with the HARPS spectrograph, mostly as complementary observations to the photometric light curves of 71 of the asteroseismological targets of the CoRoT satellite. The remaining archived spectra pertain to other, non-CoRoT targets: these objects were observed in order to better characterize the variability classes of the CoRoT targets. In the framework of the SpaceInn project, we are now presenting the deliverables D3.9, i.e. the addition of the CoRoT light curves to our archive, in order to allow the study of the simultaneous photometry and spectroscopy of the objects. A brief summary of all the work done until now (deliverables D3.8) is given. Our tasks until now have thus been the following: • the spectra have been reduced, normalized, and converted in VO-compliant FITS files (D3.8); • the mean line profiles have been computed for each spectrum (D3.8); • the radial velocity, vsin i, a binarity flag, a CaHK activity index, and an Hα emission index have been computed for each spectrum. In the case of double or multiple systems, the radial velocities and vsin i have been computed, if possible, for all the components (D3.8); • the physical parameters Teff , log g, and [Fe/H] have been computed for each target (D3.8); • the public CoRoT light curves of the 71 CoRoT targets present in our archive have been added to the archive (D3.9); • it is possible to retrieve the simultaneous spectroscopy and photometry of these 71 targets from the archive (D3.9); • we have begun working on the archive query interface and plotting capabilities (future D3.10)

the spaceinn sisma archive

The Spectroscopic Indicators in a SeisMic Archive (SISMA) has been built in the framework of the FP7 SpaceInn project to contain the 7013 HARPS spectra observed during the CoRoT asteroseismic groundbased program, along with their variability and asteroseismic indicators. The spectra pertain to 261 stars spread around the whole Herztsprung-Russell diagram: 72 of them were CoRoT targets while the others were observed in order to better characterize their variability classes. The Legacy Data lightcurves of the CoRoT targets are also stored in the archive

POE factory

L’INAF-Osservatorio Astronomico di Brera è stato uno dei primi istituti di ricerca italiani a dotarsi di personale specializzato nella comunicazione della scienza (ufficio POE, public outreach & education). Il POE arricchisce l’offerta culturale lombarda con un ricco programma di conferenze multimediali presso la due sedi, di osservazioni notturne attraverso telescopi professionali, laboratori didattici, partecipazioni a festival e iniziative. POE factory è il portale web che raccoglie e presenta le attività della sede di Milano e di Merate