Cristóbal Sifón, Felipe Menanteau, John P. Hughes, Mauricio Carrasco, L. Felipe Barrientos
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. Multi-wavelength analyses are required to understand the properties of these new sets of clusters, which are a sensitive probe of cosmology. Aims. We aim at a multi-wavelength 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 8.1m-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 (the BCG) and an accompanying red sequence of galaxies, plus many strongly lensed background galaxies including a 14"-long arc. Longslit spectroscopy of 6 cluster members shows that the cluster is at z = 0.516+/-0.002. We also targeted the most prominent lensed galaxy, and found z_arc = 1.601. From a strong lensing analysis we measure a median Einstein radius theta_E=29" and estimate an enclosed mass M_E = (2.38+/-0.55)e14 Msun. By extrapolating an NFW profile we find a total mass M_500(SL) = 6.1(+2.3,-1.2)e14 Msun. This mass is considerably lower than that implied by the SZ and X-ray observations, which may indicate a departure from the NFW profile for PLCK G004.5-19.5. The analysis of archival radio data at 843 MHz and 1.4 GHz suggest that PLCK G004.5-19.5 hosts a powerful radio relic on scales <~1 Mpc.
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http://arxiv.org/abs/1304.0686
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