The XXL survey. XXI. The environment and clustering of X-ray AGN in the XXL-South field

Melnyk, O. and Elyiv, A. and Smolčić, Vernesa and Plionis, M. and Koulouridis, E. and Fotopoulou, S. and Chiappetti, L. and Adami, C. and Baran, N. and Butler, A. and Delhaize, J. and Delvecchio, I. and Finet, F. and Huynh, M. and Lidman, C. and Pierre, M. and Pompei, E. and Vignali, C. and Surdej, J. (2018) The XXL survey. XXI. The environment and clustering of X-ray AGN in the XXL-South field. Astronomy and Astrophysics, 620. A6-1-A6-11. ISSN 0004-6361

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Context. This work is part of a series of studies focusing on the environment and the properties of the X-ray selected active galactic nuclei (AGN) population from the XXL survey. The present survey, given its large area, continuity, extensive multiwavelength coverage, and large-scale structure information, is ideal for this kind of study. Here, we focus on the XXL-South (XXL-S) field. Aims. Our main aim is to study the environment of the various types of X-ray selected AGN and investigate its possible role in AGN triggering and evolution. Methods. We studied the large-scale (>1 Mpc) environment up to redshift z = 1 using the nearest neighbour distance method to compare various pairs of AGN types.We also investigated the small-scale environment (<0.4 Mpc) by calculating the local overdensities of optical galaxies. In addition, we built a catalogue of AGN concentrations with two or more members using the hierarchical clustering method and we correlated them with the X-ray galaxy clusters detected in the XXL survey. Results. It is found that radio detected X-ray sources are more obscured than non-radio ones, though not all radio sources are obscured AGN. We did not find any significant differences in the large-scale clustering between luminous and faint X-ray AGN, or between obscured and unobscured ones, or between radio and non-radio sources. At local scales (<0.4 Mpc), AGN typically reside in overdense regions, compared to non-AGN; however, no differences were found between the various types of AGN. A majority of AGN concentrations with two or more members are found in the neighbourhood of X-ray galaxy clusters within <25–45 Mpc. Our results suggest that X-ray AGN are typically located in supercluster filaments, but they are also found in over- and underdense regions.

Item Type: Article
Keywords: X-rays: galaxies: clusters; galaxies: active; radio continuum: galaxies; quasars: general
Date: 20 December 2018
Subjects: NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Additional Information: © ESO 2017. Received 21 January 2017; Accepted 22 November 2017; Published online 20 November 2018.
Divisions: Faculty of Science > Department of Physics
Publisher: EDP Sciences
Depositing User: Vernesa Smolčić
Date Deposited: 02 May 2019 10:41
Last Modified: 06 May 2019 12:54

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