The Brera Multiscale Wavelet<i>ROSAT</i>HRI Source Catalog. I. The Algorithm

Lazzati, Davide; Campana, S.; Rosati, P.; Panzera, M. R.; Tagliaferri, G.

doi:10.1086/307788

Cited by 45 publications

(80 citation statements)

References 15 publications

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“…The analysis and source detection of HRI images, together with the simulations carried out to test the detection pipeline, are extensively described in Campana et al (1999) and Lazzati et al (1999). In this case we decided to run the detection algorithm with a single significance threshold for the sources (∼4.2 σ) corresponding to a contamination of 0.4 spurious sources per field.…”

Section: Wavelet Detection Algorithmmentioning

confidence: 99%

The Brera Multi-scale Wavelet ROSAT HRI source catalogue

Panzera

Campana

Covino

et al. 2003

A&A

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Abstract. We present the Brera Multi-scale Wavelet ROSAT HRI source catalogue (BMW-HRI) derived from all ROSAT HRI pointed observations with exposure times longer than 100 s available in the ROSAT public archives. The data were analyzed automatically using a wavelet detection algorithm suited to the detection and characterization of both point-like and extended sources. This algorithm is able to detect and disentangle sources in very crowded fields and/or in the presence of extended or bright sources. Images have been also visually inspected after the analysis to ensure verification. The final catalogue, derived from 4303 observations, consists of 29 089 sources detected with a detection probability of ≥4.2σ. For each source, the primary catalogue entries provide name, position, count rate, flux and extension along with the relative errors. In addition, results of cross-correlations with existing catalogues at different wavelengths (FIRST, IRAS, 2MASS and GSC2) are also reported. Some information is available on the web via the DIANA Interface. As an external check, we compared our catalogue with the previously available ROSHRICAT catalogue (both in its short and long versions) and we were able to recover, for the short version, ∼90% of the entries. We computed the sky coverage of the entire HRI data set by means of simulations. The complete BMW-HRI catalogue provides a sky coverage of 732 deg 2 down to a limiting flux of ∼10 −12 erg s −1 cm −2 and of 10 deg 2 down to ∼10 −14 erg s −1 cm −2 . We were able to compute the cosmological log(N)-log(S ) distribution down to a flux of 1.2 × 10 −14 erg s −1 cm −2 .

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Section: Wavelet Detection Algorithmmentioning

confidence: 99%

The Brera Multi-scale Wavelet ROSAT HRI source catalogue

Panzera

Campana

Covino

et al. 2003

A&A

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“…A rough positional accuracy estimate can be derived by the ratio HEW/(2 √ N − 1) (e.g. Lazzati et al 1998, since for a 2-dimensional Gaussian the HEW coincides with the 2 σ) where N the number of photons. So for a 10 photons detection limit a positional accuracy of ∼12 is achieved (90% confidence level).…”

Section: Need For a Wide-field Telescope For All Sky Surveysmentioning

confidence: 99%

Optimization of grazing incidence mirrors and its application to surveying X-ray telescopes

Conconi

Campana

2001

A&A

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Abstract. Grazing incidence mirrors for X-ray astronomy are usually designed in the parabola-hyperbola (Wolter I) configuration. This design allows for optimal images on-axis, which however degrade rapidly with the off-axis angle. Mirror surfaces described by polynomia (with terms higher than order two), have been put forward to improve the performances over the field of view. Here we present a refined procedure aimed at optimizing wide-field grazing incidence telescopes for X-ray astronomy. We improve the angular resolution over existing (wide-field) designs by ∼20%. We further consider the corrections for the different plate scale and focal plane curvature of the mirror shells, which sharpen by another ∼20% the image quality. This results in a factor of ∼2 reduction in the observing time needed to achieve the same sensitivity over existing wide-field designs and of ∼5 over Wolter I telescopes. We demonstrate that such wide-field X-ray telescopes are highly advantageous for deep surveys of the X-ray sky.

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“…The quoted results were all based on optically-selected AGNs. X-ray observations have found a general over-density of X-ray emitting AGNs relative to field counts in the external regions of galaxy clusters (Henry & Briel 1991;Lazzati et al 1998;Cappi et al 2001;Martini et al 2006, and references therein). However, the observed over-densities do not necessarily imply that the fraction of cluster galaxies hosting an AGN is higher than the corresponding fraction of field galaxies.…”

Section: Introductionmentioning

confidence: 99%

The AGN fraction–velocity dispersion relation in clusters of galaxies

Popesso¹,

Biviano

2006

A&A

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Context. Some previous investigations have found that the fraction ( f AGN ) of active galactic nuclei (AGNs) is lower in clusters than in the field. This can result from the suppression of galaxy-galaxy mergers in high-velocity dispersion (σ v ) clusters, if the formation and/or fueling of AGNs is directly related to the merging process. Aims. We investigate the existence of a relation between f AGN and σ v in galaxy clusters in order to shed light on the formation and evolution processes of AGNs and cluster galaxies. Results. We find a significant f AGN −σ v anti-correlation. Clusters with σ v lower and, respectively, higher than 500 km s −1 have AGN fractions of 0.21±0.01 and 0.15±0.01, on average. The f AGN −σ v relation can be described by a model that assumes f AGN is proportional to the galaxies merging rate, plus a constant. Conclusions. Since f AGN increases with decreasing σ v , AGNs are likely to have played a significant rôle in heating the intra-cluster medium and driving galaxy evolution in cluster precursors and groups.

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The Brera Multiscale WaveletROSATHRI Source Catalog. I. The Algorithm

Cited by 45 publications

References 15 publications

The Brera Multi-scale Wavelet ROSAT HRI source catalogue

The Brera Multi-scale Wavelet ROSAT HRI source catalogue

Optimization of grazing incidence mirrors and its application to surveying X-ray telescopes

The AGN fraction–velocity dispersion relation in clusters of galaxies

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