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 theta(E)(z(s) = 1.6) similar or equal to 30 '' and estimate an enclosed mass M-E = 2.45(0.47)(+0.45) x 10(14) M-circle dot. By extrapolating a Navarro-Frenk-White profile, we find a total mass M-500(SL) = 4.0(-1.0)(+2.1) x 10(14) M-circle dot. We also include a constraint on the mass from previous X-ray observations, which yields a slightly higher mass, M-500(SL+X) = 6.7(-1.3)(+2.6) x 10(14) M-circle dot, 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 less than or similar to 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.