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|Title:||The XXL Survey. XXI. The environment and clustering of X-ray AGN in the XXL-South field||Authors:||Melnyk, O.
|Issue Date:||2018||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||620||First Page:||A6||Abstract:||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. <BR /> 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. <BR /> 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. <BR /> 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.||Note:||Part of the second data release of the XXL Survey. Associated data is accessible via CDS and via the XXL Database hosted at IASF-MI||URI:||http://hdl.handle.net/20.500.12386/27584||URL:||https://www.aanda.org/articles/aa/full_html/2018/12/aa30479-17/aa30479-17.html
|Appears in Collections:||1.01 Articoli in rivista|
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