N. Aghanim, M. Arnaud, M. Ashdown, J. Aumont, C. Baccigalupi, A. Balbi, A. J. Banday, R. B. Barreiro, M. Bartelmann, J.G. Bartlett, E. Battaner, K. Benabed, A. Benoît, J.-P. Bernard, M. Bersanelli, R. Bhatia, J. J. Bock, A. Bonaldi, J. R. Bond, J. Borrill, F. R. Bouchet, M. L. Brown, M. Bucher, C. Burigana, P. Cabella, C. M. Cantalupo, J.-F. Cardoso, P. Carvalho, A. Catalano, L. Cayón, A. Challinor, A. Chamballu, L.-Y. Chiang, G. Chon, P. R. Christensen, E. Churazov, D. L. Clements, S. Colafrancesco, S. Colombi, F. Couchot, A. Coulais, B. P. Crill, F. Cuttaia, A. C. da Silva, H. Dahle, L. Danese, P. de Bernardis, G. de Gasperis, A. de Rosa, G. de Zotti, J. Delabrouille, J.-M. Delouis, F.-X. Désert, J. M. Diego, K. Dolag, S. Donzelli, O. Doré, U. Dörl, M. Douspis, X. Dupac, G. Efstathiou, T. A. Enβlin, F. Finelli, I. Flores-Cacho, O. Forni, M. Frailis, E. Franceschi, S. Fromenteau, S. Galeotta, K. Ganga, R. T. Génova-Santos, M. Giard, G. Giardino, Y. Giraud-Héraud, J. González-Nuevo, R. González-Riestra, K. M. Gorski, S. Gratton, A. Gregorio, A. Gruppuso, D. L. Harrison, P. Heinämäki, S. Henrot-Versillé, C. Hernández-Monteagudo, D. Herranz, S. R. Hildebrandt, E. Hivon, M. Hobson, W. A. Holmes, W. Hovest, R. Hoyland, K. M. Huffenberger, G. Hurier, A. H. Jaffe, M. Juvela, E. Keihänen, R. Keskitalo, T. S. Kisner, R. Kneissl, L. Knox, H. Kurki-Suonio, G. Lagache, J.-M. Lamarre, A. Lasenby, R. J. Laureijs, C. R. Lawrence, M. Le Jeune, S. Leach, R. Leonardi, A. Liddle, M. Linden-Vørnle, M. López-Caniego, P. M. Lubin, J. F. Macías-Pérez, B. Maffei, D. Maino, N. Mandolesi, R. Mann, M. Maris, F. Marleau, E. Martínez-González, S. Masi, S. Matarrese, F. Matthai, P. Mazzotta, A. Melchiorri, J.-B. Melin, L. Mendes, A. Mennella, S. Mitra, M.-A. Miville-Deschênes, A. Moneti, L. Montier, G. Morgante, D. Mortlock, D. Munshi, J. A. Murphy, P. Naselsky, P. Natoli, C. B. Netterfield, H. U. Nørgaard-Nielsen, F. Noviello, D. Novikov, I. Novikov, S. Osborne, F. Pajot, F. Pasian, G. Patanchon, O. Perdereau, L. Perotto, F. Perrotta, F. Piacentini, M. Piat, E. Pierpaoli, R. Piffaretti, S. Plaszczynski, E. Pointecouteau, G. Polenta, N. Ponthieu, T. Poutanen, G. W. Pratt, G. Prézeau, S. Prunet, J.-L. Puget, R. Rebolo López, M. Reinecke, C. Renault, S. Ricciardi, T. Riller, I. Ristorcelli, G. Rocha, C. Rosset, J. A. Rubiño-Martin, B. Rusholme, E. Saar, M. Sandri, D. Santos, B. M. Schäfer, D. Scott, M. D. Seiffert, G. F. Smoot, J.-L. Starck, F. Stivoli, V. Stolyarov, R. Sunyaev, J.-F. Sygnet, J. A. Tauber, L. Terenzi, L. Toffolatti, M. Tomasi, J.-P. Torre, M. Tristram, J. Tuovinen, L. Valenziano, L. Vibert, P. Vielva, F. Villa, N. Vittorio, B. D. Wandelt, S. D. M. White, D. Yvon, A. Zacchei, A. Zonca
We present the XMM-Newton follow-up for confirmation of Planck cluster candidates. Twenty-five candidates have been observed to date using snapshot (~10 ks) exposures, ten as part of a pilot programme to sample a low range of signal-to-noise ratios (4 < S/N < 6), and a further 15 in a programme to observe a sample of S/N > 5 candidates. The sensitivity and spatial resolution of XMM-Newton allows unambiguous discrimination between clusters and false candidates. The 4 false candidates have S/N = 4.1. A total of 21 candidates are confirmed as extended X-ray sources. Seventeen are single clusters, the majority of which are found to have highly irregular and disturbed morphologies (about ~70%). The remaining four sources are multiple systems, including the unexpected discovery of a supercluster at z = 0.45. For 20 sources we are able to derive a redshift estimate from the X-ray Fe K line (albeit of variable quality). The new clusters span the redshift range 0.09 ≤ z ≤ 0.54, with a median redshift of z ~ 0.37. A first determination is made of their X-ray properties including the characteristic size, which is used to improve the estimate of the SZ Compton parameter, Y500. The follow-up validation programme has helped to optimise the Planck candidate selection process. It has also provided a preview of the X-ray properties of these newly-discovered clusters, allowing comparison with their SZ properties, and to the X-ray and SZ properties of known clusters observed in the Planck survey. Our results suggest that Planck may have started to reveal a non-negligible population of massive dynamically perturbed objects that is under-represented in X-ray surveys. However, despite their particular properties, these new clusters appear to follow the Y500–YX relation established for X-ray selected objects, where YX is the product of the gas mass and temperature.
cosmology: observations – galaxies: clusters: general – galaxies: clusters: intracluster medium – cosmic background radiation – X-rays: galaxies: clusters
Planck is a project of the European Space Agency (ESA) with instruments provided by two scientific consortia funded by ESA member states (in particular the lead countries: France and Italy) with contributions from NASA (USA), and telescope reflectors provided in a collaboration between ESA and a scientific consortium led and funded by Denmark.
Astronomy and Astrophysics
Volume 536, Number of pages A9_1