A Method Based on Wavelet Transforms for Source Detection in Photon‐counting Detector Images. I. Theory and General Properties

Damiani, F.; Maggio, A.; Micela, G.; Sciortino, S.

doi:10.1086/304217

Cited by 198 publications

(179 citation statements)

References 9 publications

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“…PWXDetect is a version of the PWDetect tool (Damiani et al 1997), specially tuned for XMM-Newton data. It can combine data from the three EPIC detectors and from different observations, even taken with different pointings, provided that the pointing boresights are close enough that a single model for the off-axis angle dependence of the PSF can be used (in practice, this amounts to a few arcmins).…”

Section: Cataloguementioning

confidence: 99%

The XMM deep survey in the CDF-S

Ranalli¹,

Comastri²,

Vignali³

et al. 2013

A&A

128

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Nuclear obscuration plays a key role in the initial phases of AGN growth, yet not many highly obscured active galactic nuclei (AGN) are currently known beyond the local Universe, and their search is an active topic of research. The XMM-Newton survey in the Chandra Deep Field South (XMM-CDFS) aims at detecting and studying the spectral properties of a significant number of obscured and Compton-thick (N H > ∼ 10 24 cm −2 ) AGN. The large effective area of XMM-Newton in the 2-10 and 5-10 keV bands, coupled with a 3.45 Ms nominal exposure time (2.82 and 2.45 Ms after light curve cleaning for MOS and PN, respectively), allows us to build clean samples in both bands, and makes the XMM-CDFS the deepest XMM-Newton survey currently published in the 5-10 keV band. The large multi-wavelength and spectroscopic coverage of the CDFS area allows for an immediate and abundant scientific return. In this paper, we present the data reduction of the XMM-CDFS observations, the method for source detection in the 2-10 and 5-10 keV bands, and the resulting catalogues. A number of 339 and 137 sources are listed in the above bands with flux limits of 6.6 × 10 −16 and 9.5× 10 −16 erg s −1 cm −2 , respectively. The flux limits at 50% of the maximum sky coverage are 1.8× 10 −15 and 4.0× 10 −15 erg s −1 cm −2 , respectively. The catalogues have been cross-correlated with the Chandra ones: 315 and 130 identifications have been found with a likelihood-ratio method, respectively. A number of 15 new sources, previously undetected by Chandra, is found; 5 of them lie in the 4 Ms area. Redshifts, either spectroscopic or photometric, are available for ∼95% of the sources. The number counts in both bands are presented and compared to other works. The survey coverage has been calculated with the help of two extensive sets of simulations, one set per band. The simulations have been produced with a newly-developed simulator, written with the aim of the most careful reproduction of the background spatial properties. For this reason, we present a detailed decomposition of the XMM-Newton background into its components: cosmic, particle, and residual soft protons. The three components have different spatial distributions. The importance of these three components depends on the band and on the camera; the particle background is the most important one (80-90% of the background counts), followed by the soft protons (4-20%).

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Section: Cataloguementioning

confidence: 99%

The XMM deep survey in the CDF-S

Ranalli¹,

Comastri²,

Vignali³

et al. 2013

A&A

128

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“…A full account of the analysis of the Chandra observations will be provided by Flaccomio et al (in preparation). In brief, we performed source detection on each field with PWdetect (Damiani et al 1997) and then used ACIS Extract (Broos et al 2010) to extract individual source spectra and lightcurves. We here make use mainly of the mean observed fluxes during the two observations, in units of counts s −1 cm −2 , i.e., countrates divided by the effective area of the detector at each source position.…”

Section: Data and Sample Selectionmentioning

confidence: 99%

Correlated optical and X-ray variability in CTTS

Flaccomio

Micela

Favata

et al. 2010

A&A

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Aims. Optical and X-ray emission from classical T Tauri stars (CTTSs) has long been known to be highly variable. Our long, uninterrupted optical observation of the NGC 2264 region with CoRoT allows the optical variability in CTTS to be studied with unprecedented accuracy and time coverage. Two short Chandra observations obtained during the CoRoT pointing with a separation of 16 days allow us to study whether there is a correlation between optical and X-ray variability on this timescale, thus probing the physical mechanisms driving the variability in both bands. Methods. We have computed the optical and X-ray fractional variability between the two 30 ks duration windows covered by both the Chandra and CoRoT observations, for a sample of classical and weak line T Tauri stars (WTTSs) in NGC 2264. A scatter plot clearly shows that the variability of CTTSs in the optical and soft X-ray (0.5-1.5 keV) bands is correlated, while no correlation is apparent in the hard (1.5-8.0 keV) band. Also, no correlation in either band is present for WTTSs. Results. We show that the correlation between soft X-ray and optical variability of CTTSs can be naturally explained in terms of time-variable shading (absorption) from circumstellar material orbiting the star, in a scenario rather similar to the one invoked to explain the observed phenomenology in the CTTS AA Tau. The slope of the observed correlation implies (in the hypothesis of homogeneous shading) a significant dust depletion in the circumstellar material (with a gas-to-dust ratio approximately 5 times lower than the standard value for interstellar material).

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“…Source detection was accomplished with the Palermo Wavelet Detection code PWDetect 6 version 1.3.2 (Damiani et al 1997a) on the level-2 event list restricted to the 0.5-10 keV energy band and specifically compiled to run for a maximun of 7×10 6 events. PWDetect analyses the data on different spatial scales, from 0.25 to 16 arcsec, allowing the detection of both point-like and moderately extended sources and the efficient resolution of close sources pairs.…”

Section: Source Detectionmentioning

confidence: 99%

“…The most important input parameter required by the code is the final threshold significance for detection, S min (in equivalent Gaussian σs), which depends on the background level, detector, and desired number of spurious detections per field due to Poisson noise, as determined from extensive simulations of source-free fields (cf. Damiani et al 1997a). We determined the total number of background counts detected during the entire exposure over the full HRC-I detector at 4.5 ×10 6 photons with a proprietary IDL script.…”

Section: Source Detectionmentioning

confidence: 99%

HRC-I/ChandraX-ray observations towardsσ Orionis

Caballero

Colombo

López‐Santiago

2010

A&A

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Aims. We investigated the X-ray emission from young stars and brown dwarfs in the σ Orionis cluster (τ ∼ 3 Ma, d ∼ 385 pc) and its relation to mass, the presence of circumstellar discs, and separation to the cluster centre by taking advantage of the superb spatial resolution of the Chandra X-ray Observatory. Methods. We used public HRC-I/Chandra data from a 97.6 ks pointing towards the cluster centre and complemented them with X-ray data from IPC/Einstein, HRI/ROSAT, EPIC/XMM-Newton, and ACIS-S/Chandra together with optical and infrared photometry and spectroscopy from the literature and public catalogues. On our HRC-I/Chandra data, we measured count rates, estimated X-ray fluxes, and searched for short-term variability. We also looked for long-term variability by comparing with previous X-ray observations. Results. Among the 107 detected X-ray sources, there were 70 cluster stars with known signposts of youth, two young brown dwarfs, 12 cluster member candidates, four field dwarfs, and two galaxies with optical-infrared counterpart. The remaining sources were extragalactic. Based on a robust Poisson-χ 2 analysis, nine cluster stars displayed flares or rotational modulation during the HRC-I observations, while eight other stars and one brown dwarf showed X-ray flux variations between the HRC-I and IPC, HRI, and EPIC epochs. We constructed a cluster X-ray luminosity function from O9.5 (about 18 M ) to M6.5 (about 0.06 M ). We found: (i) that early-type stars in multiple systems or with spectroscopic peculiarities tend to display X-ray emission; (ii) that the two detected brown dwarfs and the least-massive star are among the σ Orionis objects with the highest L X /L J ratios; and (iii) that a large fraction of known classical T Tauri stars in the cluster are absent in this and other X-ray surveys. Finally, from a spatial distribution analysis, we quantified the impact of sensitivity degradation towards the HRC-I borders on the detection of faint X-ray sources and concluded that dozens X-ray σ Orionis stars and brown dwarfs still need to be detected.

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A Method Based on Wavelet Transforms for Source Detection in Photon‐counting Detector Images. I. Theory and General Properties

Cited by 198 publications

References 9 publications

The XMM deep survey in the CDF-S

The XMM deep survey in the CDF-S

Correlated optical and X-ray variability in CTTS

HRC-I/ChandraX-ray observations towardsσ Orionis

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