The XXL Survey

XVII. X-ray and Sunyaev-Zel’dovich properties of the redshift 2.0 galaxy cluster XLSSC 122^★,★★

¹ Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford CA 94305, USA
e-mail: amantz@slac.stanford.edu
² Department of Physics, Stanford University, 382 via Pueblo Mall, Stanford CA 94305, USA
³ Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago IL 60637, USA
⁴ Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago IL 60637, USA
⁵ SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park CA 94025, USA
⁶ Department of Physics/Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue, Chicago IL 60637, USA
⁷ H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
⁸ Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson AZ 85721, USA
⁹ Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC, Canada
¹⁰ Argelander-Institute for Astronomy, Auf dem Hügel 71, 53121 Bonn, Germany
¹¹ Service d’Astrophysique AIM, DRF/IRFU/SAp, CEA-Saclay, 91191 Gif-sur-Yvette, France

Received: 18 November 2016
Accepted: 21 March 2017

Abstract

We present results from a 100 ks XMM-Newton observation of galaxy cluster XLSSC 122, the first massive cluster discovered through its X-ray emission at z ≈ 2. The data provide the first precise constraints on the bulk thermodynamic properties of such a distant cluster, as well as an X-ray spectroscopic confirmation of its redshift. We measure an average temperature of kT = 5.0 ± 0.7 keV; a metallicity with respect to solar of Z/Z_⊙ = 0.33_−0.17^+0.19, consistent with lower-redshift clusters; and a redshift of z = 1.99^+0.07_-0.06 , consistent with the earlier photo-z estimate. The measured gas density profile leads to a mass estimate at r₅₀₀ of M₅₀₀ = (6.3 ± 1.5) × 10¹³ M_⊙. From CARMA 30 GHz data, we measure the spherically integrated Compton parameter within r₅₀₀ to be Y ₅₀₀ = (3.6 ± 0.4) × 10⁻¹². We compare the measured properties of XLSSC 122 to lower-redshift cluster samples, and find good agreement when assuming the simplest (self-similar) form for the evolution of cluster scaling relations. While a single cluster provides limited information, this result suggests that the evolution of the intracluster medium in the most massive, well-developed clusters is remarkably simple, even out to the highest redshifts where they have been found. At the same time, our data reaffirm the previously reported spatial offset between the centres of the X-ray and SZ signals for XLSSC 122, suggesting a disturbed configuration. Higher spatial resolution data could thus provide greater insights into the internal dynamics of this system.