Article (Scientific journals)
The XXL Survey: XII. Optical spectroscopy of X-ray-selected clusters and the frequency of AGN in superclusters
Koulouridis, E.; Poggianti, B.; Altieri, B. et al.
2016In Astronomy and Astrophysics, 592
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Keywords :
Galaxies: active; Galaxies: clusters: general; Galaxies: evolution; Galaxies: interactions; Large-scale structure of Universe; X-rays: galaxies: clusters; Spectroscopic analysis; Surveys; Galaxies : active; Galaxies: evolutions; Large scale structure of universe; X rays: galaxies: clusters; Galaxies
Abstract :
[en] Context. This article belongs to the first series of XXL publications. It presents multifibre spectroscopic observations of three 0.55 deg2 fields in the XXL Survey, which were selected on the basis of their high density of X-ray-detected clusters. The observations were obtained with the AutoFib2+WYFFOS (AF2) wide-field fibre spectrograph mounted on the 4.2 m William Herschel Telescope. Aims. The paper first describes the scientific rationale, the preparation, the data reduction, and the results of the observations, and then presents a study of active galactic nuclei (AGN) within three superclusters. Methods. To determine the redshift of galaxy clusters and AGN, we assign high priority to a) the brightest cluster galaxies (BCGs), b) the most probable cluster galaxy candidates, and c) the optical counterparts of X-ray point-like sources. We use the outcome of the observations to study the projected (2D) and the spatial (3D) overdensity of AGN in three superclusters. Results. We obtained redshifts for 455 galaxies in total, 56 of which are counterparts of X-ray point-like sources. We were able to determine the redshift of the merging supercluster XLSSC-e, which consists of six individual clusters at z ~ 0.43, and we confirmed the redshift of supercluster XLSSC-d at z ~ 0.3. More importantly, we discovered a new supercluster, XLSSC-f, that comprises three galaxy clusters also at z ~ 0.3. We find a significant 2D overdensity of X-ray point-like sources only around the supercluster XLSSC-f. This result is also supported by the spatial (3D) analysis of XLSSC-f, where we find four AGN with compatible spectroscopic redshifts and possibly one more with compatible photometric redshift. In addition, we find two AGN (3D analysis) at the redshift of XLSSC-e, but no AGN in XLSSC-d. Comparing these findings with the optical galaxy overdensity we conclude that the total number of AGN in the area of the three superclusters significantly exceeds the field expectations. All of the AGN found have luminosities below 7 × 1042 erg s-1. Conclusions. The difference in the AGN frequency between the three superclusters cannot be explained by the present study because of small number statistics. Further analysis of a larger number of superclusters within the 50 deg2 of the XXL is needed before any conclusions on the effect of the supercluster environment on AGN can be reached. © ESO, 2016.
Research center :
Greek General Secretariat of Research and Technology
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Koulouridis, E.;  Service d'Astrophysique AIM, DSM/IRFU/SAp, CEA Saclay, Gif-sur-Yvette, France, Institute for Astronomy and Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Palaia Penteli, Athens, Greece
Poggianti, B.;  INAF-Astronomical Observatory of Padova, Vicolo Osservatorio 5, Padova, Italy
Altieri, B.;  European Space Astronomy Centre (ESA/ESAC), Operations Department, Villanueva de la Canãda, Madrid, Spain
Valtchanov, I.;  European Space Astronomy Centre (ESA/ESAC), Operations Department, Villanueva de la Canãda, Madrid, Spain
Jaffé, Y.;  Department of Astronomy, Universidad de Concepción, Casilla 160-C, Concepción, Chile
Adami, C.;  LAM, OAMP, Université Aix-Marseille, CNRS, Pôle de l'Étoile, Site de Chãteau Gombert, 38 rue Frédéric Joliot-Curie, Marseille 13 Cedex, France
Elyiv, A.;  Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, Bologna, Italy, Main Astronomical Observatory, Academy of Sciences of Ukraine, 27 Akademika Zabolotnoho St., Kyiv, Ukraine
Melnyk, O.;  Department of Physics, University of Zagreb, Bijenicka cesta 32, Zagreb, Croatia, Astronomical Observatory, Taras Shevchenko National University of Kyiv, 3 Observatorna St., Kyiv, Ukraine
Fotopoulou, S.;  Department of Astronomy, University of Geneva, Chemin d'Écogia 16, Versoix, Switzerland
Gastaldello, F.;  INAF-IASF-Milano, via Bassini 15, Milano, Italy
Horellou, C.;  Dept. of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden
Pierre, M.;  Service d’Astrophysique AIM, DSM / IRFU / SAp, CEA Saclay, F-91191 Gif sur Yvette, France
Pacaud, F.;  Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, Bonn, Germany
Plionis, M.;  Institute for Astronomy and Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Palaia Penteli, Athens, Greece, Physics Department of Aristotle University of Thessaloniki, University Campus, Thessaloniki, Greece, Instituto Nacional de Astrofísica Optica y Electrónica, Puebla, CP, Mexico
Sadibekova, T.;  Service d'Astrophysique AIM, DSM/IRFU/SAp, CEA Saclay, Gif-sur-Yvette, France
Surdej, Jean  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)
More authors (6 more) Less
Language :
English
Title :
The XXL Survey: XII. Optical spectroscopy of X-ray-selected clusters and the frequency of AGN in superclusters
Publication date :
2016
Journal title :
Astronomy and Astrophysics
ISSN :
0004-6361
eISSN :
1432-0746
Publisher :
EDP Sciences
Volume :
592
Peer reviewed :
Peer Reviewed verified by ORBi
Name of the research project :
NEWFELPRO fellowship project in Croatia
Funders :
CNES - Centre National d'Études Spatiales [FR]
CNRS - Centre National de la Recherche Scientifique [FR]
FONDECYT - Chile Fondo Nacional de Desarrollo Científico y Tecnológico [CL]
NASA - National Aeronautics and Space Administration [US-DC] [US-DC]
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