4.6 Article

Angular correlation functions of X-ray point-like sources in the full exposure XMM-LSS field

期刊

ASTRONOMY & ASTROPHYSICS
卷 537, 期 -, 页码 -

出版社

EDP SCIENCES S A
DOI: 10.1051/0004-6361/201117983

关键词

X-rays: galaxies; galaxies: active; surveys

资金

  1. ESA PRODEX
  2. Belgian Federal Science Policy Office
  3. Communaute francaise de Belgique - Actions de recherche concertees - Academie universitaire Wallonie-Europe
  4. Grants-in-Aid for Scientific Research [21740152] Funding Source: KAKEN

向作者/读者索取更多资源

Aims. Our aim is to study the large-scale structure of different types of AGN using the medium-deep XMM-LSS survey. Methods. We measure the two-point angular correlation function of similar to 5700 and 2500 X-ray point-like sources over the similar to 11 sq. deg. XMM-LSS field in the soft (0.5-2 keV) and hard (2-10 keV) bands. For the conversion from the angular to the spatial correlation function we used the Limber integral equation and the luminosity-dependent density evolution model of the AGN X-ray luminosity function. Results. We have found significant angular correlations with the power-law parameters gamma = 1.81 +/- 0.02, theta(0) = 1.3 '' +/- 0.2 '' for the soft, and gamma = 2.00 +/- 0.04, theta(0) = 7.3 '' +/- 1.0 '' for the hard bands. The amplitude of the correlation function w(theta) is higher in the hard than in the soft band for f(x) less than or similar to 10(-14) erg s(-1) cm(-2) and lower above this flux limit. We confirm that the clustering strength theta(0) grows with the flux limit of the sample, a trend which is also present in the amplitude of the spatial correlation function, but only for the soft band. In the hard band, it remains almost constant with r(0) similar or equal to 10 h(-1) Mpc, irrespective of the flux limit. Our analysis of AGN subsamples with different hardness ratios shows that the sources with a hard-spectrum are more clustered than soft-spectrum ones. This result may be a hint that the two main types of AGN populate different environments. Finally, we find that our clustering results correspond to an X-ray selected AGN bias factor of similar to 2.5 for the soft band sources (at a median (z) over bar similar or equal to 1.1) and similar to 3.3 for the hard band sources (at a median (z) over bar similar or equal to 1), which translates into a host dark matter halo mass of similar to 10(13) h(-1) M-circle dot and similar to 10(13.7) h(-1) M-circle dot for the soft and hard bands, respectively.

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