Planck intermediate results. VIII. Filaments between interacting clusters

Zacchei, A.; Zonca, A.; White, S. D. M.; Yvon, D.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Welikala, N.; Van Tent, B.; Vielva, P.; Villa, F.; Tristram, M.; Tucci, M.; Valenziano, L.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Scott, D.; Smoot, G. F.; Starck, J.-L.; Sandri, M.; Savini, G.; Schaefer, B. M.; Rossetti, M.; Rubiño-Martín, J. A.; Rusholme, B.; Rocha, G.; Roman, M.; Rosset, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Reinecke, M.; Remazeilles, M.; Renault, C.; Rachen, J. P.; Rebolo, R.; Prunet, S.; Puget, J.-L.; Poutanen, T.; Pratt, G. W.; Ponthieu, N.; Popa, L.; Piffaretti, R.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Perdereau, O.; Perotto, L.; Perrotta, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Novikov, D.; Novikov, I.; Osborne, S.; Pajot, F.; Nørgaard-Nielsen, H. U.; Noviello, F.; Nati, F.; Natoli, P.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Montier, L.; Morgante, G.; Miville-Deschènes, M.-A.; Moneti, A.; Mennella, A.; Mitra, S.; Melin, J.-B.; Mendes, L.; Matthai, F.; Mazzotta, P.; Mei, S.; Melchiorri, A.; Massardi, M.; Matarrese, S.; Marshall, D. J.; Martínez-González, E.; Masi, S.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Marleau, F.; Lubin, P. M.; Luzzi, G.; Macías-Pérez, J. F.; Linden-Vørnle, M.; López-Caniego, M. et al.
Bibliographical reference

Astronomy and Astrophysics, Volume 550, id.A134, 16 pp.

Advertised on:
2
2013
Number of authors
208
IAC number of authors
4
Citations
99
Refereed citations
97
Description
Context. About half of the baryons of the Universe are expected to be in the form of filaments of hot and low-density intergalactic medium. Most of these baryons remain undetected even by the most advanced X-ray observatories, which are limited in sensitivity to the diffuse low-density medium. Aims: The Planck satellite has provided hundreds of detections of the hot gas in clusters of galaxies via the thermal Sunyaev-Zel'dovich (tSZ) effect and is an ideal instrument for studying extended low-density media through the tSZ effect. In this paper we use the Planck data to search for signatures of a fraction of these missing baryons between pairs of galaxy clusters. Methods: Cluster pairs are good candidates for searching for the hotter and denser phase of the intergalactic medium (which is more easily observed through the SZ effect). Using an X-ray catalogue of clusters and the Planck data, we selected physical pairs of clusters as candidates. Using the Planck data, we constructed a local map of the tSZ effect centred on each pair of galaxy clusters. ROSAT data were used to construct X-ray maps of these pairs. After modelling and subtracting the tSZ effect and X-ray emission for each cluster in the pair, we studied the residuals on both the SZ and X-ray maps. Results: For the merging cluster pair A399-A401 we observe a significant tSZ effect signal in the intercluster region beyond the virial radii of the clusters. A joint X-ray SZ analysis allows us to constrain the temperature and density of this intercluster medium. We obtain a temperature of kT = 7.1 ± 0.9 keV (consistent with previous estimates) and a baryon density of (3.7 ± 0.2) × 10-4 cm-3. Conclusions: The Planck satellite mission has provided the first SZ detection of the hot and diffuse intercluster gas.
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