Letter to the Editor

Extended X-ray emission in PKS 1718−649

¹ Anton Pannekoek Institute for Astronomy, Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
e-mail: tobias.beuchert@sternwarte.uni-erlangen.de
² Dr. Remeis-Observatory & Erlangen Centre for Astroparticle Physics, Universität Erlangen-Nürnberg, Sternwartstrasse 7, 96049 Bamberg, Germany
³ Lehrstuhl für Astronomie, Universität Würzburg, Emil-Fischer-Straße 31, 97074 Würzburg, Germany
⁴ Laboratório Nacional de Astrofísica/MCTIC, Rua dos Estados Unidos, 154, Bairro das Naçñes, Itajubá, MG, Brazil
⁵ Instituto de Astrofísica de Canarias, C/Vía Láctea, s/n, 38206 La Laguna, Tenerife, Spain
⁶ Netherlands Institute for Radio Astronomy (ASTRON), PO Bus 2, 7990AA Dwingeloo, The Netherlands
⁷ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁸ GRAPPA & Anton Pannekoek Institute for Astronomy, Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
⁹ INAF-Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius (CA), Italy
¹⁰ IMAPP/Department of Astrophysics, Radboud University, PO box 9010, 6500 GL Nijmegen, The Netherlands
¹¹ NASA/GSFC, Mail Code: 661, Greenbelt, MD 20771, USA
¹² Observatori Astronòmic, Universitat de València, Parc Científic, C. Catedrático José Beltrán 2, 46980 Paterna, València, Spain
¹³ Departament d’Astronomia i Astrofísica, Universitat de València, C. Dr. Moliner 50, 46100 Burjassot, València, Spain
¹⁴ International Centre for Radio Astronomy Research (ICRAR), Curtin University, Bentley, WA 6102, Australia

Received: 20 March 2018
Accepted: 8 April 2018

Abstract

PKS 1718−649 is one of the closest and most comprehensively studied candidates of a young active galactic nucleus (AGN) that is still embedded in its optical host galaxy. The compact radio structure, with a maximal extent of a few parsecs, makes it a member of the group of compact symmetric objects (CSO). Its environment imposes a turnover of the radio synchrotron spectrum towards lower frequencies, also classifying PKS 1718−649 as gigahertz-peaked radio spectrum (GPS) source. Its close proximity has allowed the first detection of extended X-ray emission in a GPS/CSO source with Chandra that is for the most part unrelated to nuclear feedback. However, not much is known about the nature of this emission. By co-adding all archival Chandra data and complementing these datasets with the large effective area of XMM-Newton, we are able to study the detailed physics of the environment of PKS 1718−649. Not only can we confirm that the bulk of the ≲kiloparsec-scale environment emits in the soft X-rays, but we also identify the emitting gas to form a hot, collisionally ionized medium. While the feedback of the central AGN still seems to be constrained to the inner few parsecs, we argue that supernovae are capable of producing the observed large-scale X-ray emission at a rate inferred from its estimated star formation rate.