Issue |
A&A
Volume 557, September 2013
|
|
---|---|---|
Article Number | A81 | |
Number of page(s) | 14 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201220624 | |
Published online | 05 September 2013 |
Classification and environmental properties of X-ray selected point-like sources in the XMM-LSS field⋆
1
Institut d’Astrophysique et de Géophysique, Université de
Liège,
4000
Liège,
Belgium
e-mail: melnykol@gmail.com
2
Astronomical Observatory, Taras Shevchenko National University of
Kyiv, 3 Observatorna St., 04053
Kyiv,
Ukraine
3
Physics Dept., Aristotle Univ. of Thessaloniki,
54124
Thessaloniki,
Greece
4
Instituto Nacional de Astrófisica, Óptica y Electrónica, 72000
Puebla,
Mexico
5
Main Astronomical Observatory, Academy of Sciences of
Ukraine, 27 Akademika Zabolotnoho
St., 03680
Kyiv,
Ukraine
6
Max-Planck-Institute for Extraterrestrial Physics,
Giessenbachstrasse 1,
85748
Garching,
Germany
7
Excellence Cluster, Boltzmannstrass 2,
85748
Garching,
Germany
8
INAF-IASF Milano, via Bassini 15, 20133
Milano,
Italy
9
Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency,
3-1-1
Yoshinodai, Chuo-ku, Sagamihara, 252−5210,
Kanagawa,
Japan
10
DSM/Irfu/SAp, CEA/Saclay, 91191
Gif-sur-Yvette Cedex,
France
Received: 24 October 2012
Accepted: 1 July 2013
Context. The XMM-Large Scale Structure survey, covering an area of 11.1 sq. deg., contains more than 6000 X-ray point-like sources detected with the XMM-Newton to a flux of 3 × 10-15 erg s-1 cm-2 in the [0.5−2] keV band. The vast majority of these sources have optical (CFHTLS), infrared (SWIRE IRAC and MIPS), near-infrared (UKIDSS), and/or ultraviolet (GALEX) counterparts.
Aims. We wish to investigate the environmental properties of the different types of the XMM-LSS X-ray sources by defining their environment using the i′-band CFHTLS W1 catalog of optical galaxies to a magnitude limit of 23.5 mag.
Methods. We have classified 4435 X-ray selected sources on the basis of their spectra, SEDs, and X-ray luminosity, and estimated their photometric redshifts, which have a 4−11 band photometry with an accuracy of σ△z/(1+zsp) = 0.076 with 22.6% outliers for i′ < 26 mag. We estimated the local overdensities of 777 X-ray sources that have spectro-z or photo-z calculated by using more than seven bands (accuracy of σ△z/(1+zsp) = 0.061 with 13.8% outliers) within the volume-limited region defined by 0.1 ≤ z ≤ 0.85 and −23.5 < Mi′ < −20.
Results. Although X-ray sources may be found in variety of environments, a high fraction (≳55−60%), as verified by comparing with the random expectations, reside in overdense regions. The galaxy overdensities within which X-ray sources reside show a positive recent redshift evolution (at least for the range studied; z ≲ 0.85). We also find that X-ray selected galaxies, when compared to AGN, inhabit significantly higher galaxy overdensities, although their spatial extent appear to be smaller than that of AGN. Hard AGN (HR ≥ −0.2) are located in more overdense regions than soft AGN (HR < −0.2), which is clearly seen in both redshift ranges, although it appears to be stronger in the higher redshift range (0.55 < z < 0.85). Furthermore, the galaxy overdensities (with δ ≳ 1.5) within which soft AGN are embedded appear to evolve more rapidly compared to the corresponding overdensities around hard AGN.
Key words: quasars: general / X-rays: general / galaxies: active / X-rays: galaxies
Full Table 2 in only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/557/A81
© ESO, 2013
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