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Title: The XMM-Newton Wide Angle Survey (XWAS)
Authors: Esquej, P.
Page, M.
Carrera, F. J.
Mateos, S.
Tedds, J.
Watson, M. G.
Corral, A.
Ebrero, J.
Krumpe, M.
Rosen, S. R.
Ceballos, M. T.
Schwope, A.
Page, C. G.
Alonso-Herrero, A.
Caccianiga, A.
Della Ceca, R.
Gonzalez-Martin, O.
Lamer, G.
Severgnini, P.
First Published: 18-Sep-2013
Publisher: EDP Sciences for European Southern Observatory (ESO), Springer Verlag (Germany) [Former Publisher]
Citation: Astronomy and Astrophysics, 557, A123 (2013)
Abstract: Aims. This programme is aimed at obtaining one of the largest X-ray selected samples of identified active galactic nuclei to date in order to characterise such a population at intermediate fluxes, where most of the Universe’s accretion power originates. We present the XMM-Newton Wide Angle Survey (XWAS), a new catalogue of almost a thousand X-ray sources spectroscopically identified through optical observations. Methods. A sample of X-ray sources detected in 68 XMM-Newton pointed observations was selected for optical multi-fibre spectroscopy. Optical counterparts and corresponding photometry of the X-ray sources were obtained from the SuperCOSMOS Sky Survey. Candidates for spectroscopy were initially selected with magnitudes down to R ∼ 21, with preference for X-ray sources having a flux F0.5−4.5 keV ≥ 10−14 erg s−1 cm−2. Optical spectroscopic observations were made using the Two Degree Field of the Anglo Australian Telescope, and the resulting spectra were classified based on optical emission lines. Results. We have identified through optical spectroscopy 940 X-ray sources over Ω ∼ 11.8 deg2 of the sky. Source populations in our sample can be summarised as 65% broad line active galactic nuclei (BLAGN), 16% narrow emission line galaxies (NELGs), 6% absorption line galaxies (ALGs) and 13% stars. An active nucleus is also likely to be present in the large majority of the X-ray sources spectroscopically classified as NELGs or ALGs. Sources lie in high-galactic latitude (|b| > 20 deg) XMM-Newton fields mainly in the southern hemisphere. Owing to the large parameter space in redshift (0 ≤ z ≤ 4.25) and flux (10−15 ≤ F0.5−4.5 keV ≤ 10−12 erg s−1 cm−2) covered by the XWAS this work provides an excellent resource for the further study of subsamples and particular cases. The overall properties of the extragalactic objects are presented in this paper. These include the redshift and luminosity distributions, optical and X-ray colours and X-ray-to-optical flux ratios.
DOI Link: 10.1051/0004-6361/201218832
ISSN: 0004-6361
eISSN: 1432-0746
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Creative Commons “Attribution Non-Commercial No Derivatives” licence CC BY-NC-ND, further details of which can be found via the following link: Archived with reference to SHERPA/RoMEO and publisher website.
Description: Reduced spectra (FITS files) are available at the CDS via anonymous ftp to ( or via
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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