Planck early results XXVI: Detection with Planck and confirmation by XMM-Newton of PLCK G266.6-27.3, an exceptionally X-ray luminous and massive galaxy cluster at z ∼ 1

N. Aghanim, M. Arnaud, M. Ashdown, F. Atrio-Barandela, J. Aumont, C. Baccigalupi, A. Balbi, A. J. Banday, R. B. Barreiro, J.G. Bartlett, E. Battaner, K. Benabed, J.-P. Bernard, M. Bersanelli, R. Bhatia, H. Böhringer, A. Bonaldi, J. R. Bond, S. Borgani, J. Borrill, F. R. Bouchet, M. L. Brown, C. Burigana, P. Cabella, C. M. Cantalupo, B. Cappellini, P. Carvalho, A. Catalano, L. Cayón, L.-Y. Chiang, C. Chiang, G. Chon, P. R. Christensen, E. Churazov, D. L. Clements, S. Colafrancesco, S. Colombi, B. P. Crill, F. Cuttaia, A. C. da Silva, H. Dahle, L. Danese, O. D'Arcangelo, R. J. Davis, P. de Bernardis, G. de Gasperis, G. de Zotti, J. Delabrouille, J.-M. Delouis, J. Démoclès, F.-X. Désert, C. Dickinson, J. M. Diego, H. Dole, S. Donzelli, O. Doré, M. Douspis, X. Dupac, G. Efstathiou, T. A. Enβlin, H. K. Eriksen, F. Finelli, I. Flores-Cacho, O. Forni, P. Fosalba, M. Frailis, E. Franceschi, S. Fromenteau, S. Galeotta, K. Ganga, R. T. Génova-Santos, M. Giard, J. González-Nuevo, R. González-Riestra, K. Górski, A. Gregorio, A. Gruppuso, F. K. Hansen, D. L. Harrison, P. Heinämäki, C. Hernández-Monteagudo, S. R. Hildebrandt, E. Hivon, M. Hobson, G. Hurier, A. H. Jaffe, W. C. Jones, M. Juvela, E. Keihänen, R. Keskitalo, T. S. Kisner, R. Kneissl, H. Kurki-Suonio, A. Lähteenmäki, J.-M. Lamarre, A. Lasenby, C. R. Lawrence, M. Le Jeune, S. Leach, R. Leonardi, C. Leroy, A. R. Liddle, P. B. Lilje, M. López-Caniego, G. Luzzi, J. F. Macías-Pérez, D. Maino, N. Mandolesi, F. Marleau, E. Martínez-González, S. Masi, S. Matarrese, P. Mazzotta, P. R. Meinhold, A. Melchiorri, J.-B. Melin, L. Mendes, A. Mennella, M.-A. Miville-Deschênes, A. Moneti, L. Montier, G. Morgante, D. Munshi, P. Naselsky, P. Natoli, J. Nevalainen, H. U. Nørgaard-Nielsen, F. Noviello, I. Novikov, I. J. O'Dwyer, S. Osborne, R. Paladini, F. Pasian, G. Patanchon, T. J. Pearson, O. Perdereau, L. Perotto, F. Perrotta, F. Piacentini, E. Pierpaoli, R. Piffaretti, P. Platania, E. Pointecouteau, G. Polenta, N. Ponthieu, L. A. Popa, T. Poutanen, G. W. Pratt, G. Prézeau, S. Prunet, J.-L. Puget, J. P. Rachen, R. Rebolo López, M. Reinecke, C. Renault, S. Ricciardi, T. Riller, I. Ristorcelli, G. Rocha, J. A. Rubiño-Martin, E. Saar, M. Sandri, G. Savini, B. M. Schäfer, D. Scott, G. F. Smoot, J.-L. Starck, D. Sutton, J.-F. Sygnet, J. A. Tauber, L. Terenzi, L. Toffolatti, M. Tomasi, M. Tristram, M. Türler, L. Valenziano, P. Vielva, F. Villa, N. Vittorio, L. A. Wade, B. D. Wandelt, J. Weller, S. D. M. White, M. White, D. Yvon, A. Zacchei, A. Zonca

Abstract
We present first results on PLCKG266.6-27.3, a galaxy cluster candidate detected at a signal-to-noise ratio of 5 in the Planck All Sky survey. An XMM-Newton validation observation has allowed us to confirm that the candidate is a bona fide galaxy cluster. With these X-ray data we measure an accurate redshift, z = 0.94 ± 0.02, and estimate the cluster mass to be M₅₀₀ = (7.8 ± 0.8) × 10¹⁴ M_☉. PLCKG266.6-27.3 is an exceptional system: its luminosity of L_X[0.5–2.0keV] = (1.4±0.05)×10⁴⁵ erg s^-1 equals that of the two most luminous known clusters in the z > 0.5 universe, and it is one of the most massive clusters at z ~ 1. Moreover, unlike the majority of high redshift clusters, PLCKG266.6-27.3 appears to be highly relaxed. This observation confirms Planck’s capability to detect high redshift, high mass clusters, and opens the way to the systematic study of population evolution in the exponential tail of the mass function.

Keywords
cosmology: observations – galaxies: clusters: general – galaxies: clusters: intracluster medium – X-rays: galaxies: clusters – cosmic background radiation

Astronomy and Astrophysics
Volume 536, Page A26_1
December 2011

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