The XXL Survey

XXXIV. Double Irony in XXL-North: a tale of two radio galaxies in a supercluster at z = 0.14^★

¹ Chalmers University of Technology, Department of Space, Earth and Environment, Onsala Space Observatory, 439 92 Onsala, Sweden
e-mail: cathy.horellou@chalmers.se
² Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands
³ Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia
⁴ Aix Marseille Univ., CNRS, CNES, LAM, Marseille, France
⁵ Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Bd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
⁶ H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
⁷ Departamento de Astronomía, DCNE-CGT, Universidad de Guanajuato; Callejón de Jalisco, s/n, Col. Valenciana, 36240, Guanajuato, Gto., Mexico
⁸ INAF, IASF Milano, via Bassini 15, 20133 Milano, Italy
⁹ Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
¹⁰ INAF – Astronomical Observatory of Padova, 35122 Padova, Italy
¹¹ Inter-University Centre for Astronomy and Astrophysics, Pune 411007, India
¹² Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹³ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
¹⁴ Dipartimento di Fisica e Astronomia, Alma Mater Studiorum, Università degli Studi di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
¹⁵ INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti 93/3, 40129 Bologna, Italy
¹⁶ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching bei München, Germany

Received: 6 March 2018
Accepted: 12 July 2018

Abstract

Aims. We show how the XXL multiwavelength survey can be used to shed light on radio galaxies and their environment.

Methods. Two prominent radio galaxies were identified in a visual examination of the mosaic of XXL-North obtained with the Giant Metrewave Radio Telescope at 610 MHz. Counterparts were searched for in other bands. Spectroscopic redshifts from the GAMA database were used to identify clusters and/or groups of galaxies, estimate their masses with the caustic method, and quantify anisotropies in the surrounding galaxy distribution via a Fourier analysis.

Results. Both radio galaxies are of FR I type and are hosted by early-type galaxies at a redshift of 0.138. The first radio source, named the Exemplar, has a physical extent of ~400 kpc; it is located in the cluster XLSSC 112, which has a temperature of ~2 keV, a total mass of ~10¹⁴ M_⊙, and resides in an XXL supercluster with eight known members. The second source, named the Double Irony, is a giant radio galaxy with a total length of about 1.1 Mpc. Its core coincides with a cataloged point-like X-ray source, but no extended X-ray emission from a surrounding galaxy cluster was detected. However, from the optical data we determined that the host is the brightest galaxy in a group that is younger, less virialized, and less massive than the Exemplar’s cluster. A friends-of-friends analysis showed that the Double Irony’s group is a member of the same supercluster as the Exemplar. There are indications that the jets and plumes of the Double Irony have been deflected by gas associated with the surrounding galaxy distribution. Another overdensity of galaxies (the tenth) containing a radio galaxy was found to be associated with the supercluster.

Conclusions. Radio Galaxies can be used to find galaxy clusters/groups that are below the current sensitivity of X-ray surveys.