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Publication details for Dr Sotiria Fotopoulou

Horellou, C., Intema, H. T., Smolčić, V., Nilsson, A., Karlsson, F., Krook, C., Tolliner, L., Adami, C., Benoist, C., Birkinshaw, M., Caretta, C., Chiappetti, L., Delhaize, J., Ferrari, C., Fotopoulou, S., Guglielmo, V., Kolokythas, K., Pacaud, F., Pierre, M., Poggianti, B. M., Ramos-Ceja, M. E., Raychaudhury, S., Röttgering, H. J. A. & Vignali, C. (2018). The XXL Survey: XXXIV. Double Irony in XXL-North: a tale of two radio galaxies in a supercluster at z = 0.14. Astronomy & Astrophysics 620: A19.

Author(s) from Durham


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.