Strong lensing analysis of PLCK G004.5–19.5, a Planck-discovered cluster hosting a radio relic at z = 0.52^⋆

¹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
e-mail: sifon@strw.leidenuniv.nl
² National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, 1205 W. Clark St, Urbana IL 61801, USA
³ University of Illinois at Urbana-Champaign, Department of Astronomy, 1002 W. Green Street, Urbana IL 61801, USA
⁴ Rutgers University, Department of Physics & Astronomy, 136 Frelinghuysen Rd, Piscataway NJ 08854, USA
⁵ Departamento de Astronomía y Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, 22 Santiago, Chile
⁶ Zentrum für Astronomie, Institut für Theoretische Astrophysik, Philosophenweg 12, 69120 Heidelberg, Germany

Received: 4 April 2013
Accepted: 5 December 2013

Abstract

Context. The recent discovery of a large number of galaxy clusters using the Sunyaev-Zel’dovich (SZ) effect has opened a new era on the study of the most massive clusters in the Universe. Multiwavelength analyses are required to understand the properties of these new sets of clusters, which are a sensitive probe of cosmology.

Aims. We aim for a multiwavelength characterization of PLCK G004.5−19.5, one of the most massive X-ray validated SZ effect-selected galaxy clusters discovered by the Planck satellite.

Methods. We have observed PLCK G004.5−19.5 with GMOS on the 8.1 m-Gemini South Telescope for optical imaging and spectroscopy, and performed a strong lensing analysis. We also searched for associated radio emission in published catalogs.

Results. An analysis of the optical images confirms that this is a massive cluster, with a dominant central galaxy and an accompanying red sequence of galaxies, plus a 14″-long strong lensing arc. Longslit spectroscopy of six cluster members shows that the cluster is at z = 0.516 ± 0.002. We also targeted the strongly lensed arc, and found z_arc = 1.601. We use LensTool to carry out a strong lensing analysis, from which we measure a median Einstein radius θ_E(z_s = 1.6) ≃ 30″ and estimate an enclosed mass M_E = 2.45_-0.47^+0.45 × 10¹⁴ M_⊙. By extrapolating a Navarro-Frenk-White profile, we find a total mass M₅₀₀^SL = 4.0_-1.0^+2.1 × 10¹⁴ M_⊙. We also include a constraint on the mass from previous X-ray observations, which yields a slightly higher mass, M₅₀₀^SL+X = 6.7_-1.3^+2.6 × 10¹⁴ M_⊙, consistent with the value from strong lensing alone. Intermediate-resolution radio images from the TIFR GMRT Sky Survey at 150 MHz reveal that PLCK G004.5−19.5 hosts a powerful radio relic on scales ≲500 kpc. Emission at the same location is also detected in low-resolution images at 843 MHz and 1.4 GHz. This is one of the higher redshift radio relics known to date.