Clustering of X-ray selected active galactic nuclei |
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| Authors: | F J Carrera X Barcons A C Fabian G Hasinger K O Mason R G McMahon J P D Mittaz & M J Page |
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| Institution: | Instituto de Física de Cantabria (Consejo Superior de Investigaciones Científicas —Universidad de Cantabria), Avenida de los Castros, 39005 Santander, Spain,;Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT,;Institute of Astronomy, Madingley Road, Cambridge CB3 0HA,;Astrophysikalisches Institut Potsdam, An der Sternwarte 16, Potsdam, Germany |
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| Abstract: | A total of 235 active galactic nuclei (AGN) from two different soft X-ray surveys the ROSAT Deep Survey (DRS) and the ROSAT International X-ray Optical Survey (RIXOS)] with redshifts between 0 and 3.5 are used to study the clustering of X-ray selected AGN and its evolution. A 2σ significant detection of clustering of such objects is found on scales < 40–80 h −1 Mpc in the RIXOS sample, while no clustering is detected on any scales in the DRS sample. Assuming a single power-law model for the spatial correlation function (SCF), quantitative limits on the AGN clustering have been obtained: a comoving correlation length 1.5 ≲ r 0 ≲ 3.3 h −1 Mpc is implied for comoving evolution, while 1.9 ≲ r 0 ≲ 4.8 for stable clustering and 2.2 ≲ r 0 ≲ 5.5 for linear evolution. These values are consistent with the correlation lengths and evolutions obtained for galaxy samples, but imply smaller amplitude or faster evolution than recent ultraviolet and optically selected AGN samples. We also constrain the ratio of bias parameters between X-ray selected AGN and IRAS galaxies to be ≲ 1.7 on scales ≲ 10 h −1 Mpc, a somewhat smaller value than is inferred from local large-scale dynamical studies. |
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| Keywords: | surveys galaxies: active galaxies: clusters: general quasars: general large-scale structure of Universe X-rays: general |
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