Clusters of galaxies are the most massive gravitationally bound objects in the Universe and are still forming. They are thus important probes1 of cosmological parameters and many astrophysical processes. However, knowledge of the dynamics of the pervasive hot gas, the mass of which is much larger than the combined mass of all the stars in the cluster, is lacking. Such knowledge would enable insights into the injection of mechanical energy by the central supermassive black hole and the use of hydrostatic equilibrium for determining cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50-million-kelvin diffuse hot plasma filling its gravitational potential well. The active galactic nucleus of the central galaxy NGC 1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These bubbles probably induce motions in the intracluster medium and heat the inner gas, preventing runaway radiative cooling—a process known as active galactic nucleus feedback2,3,4,5,6. Here we report X-ray observations of the core of the Perseus cluster, which reveal a remarkably quiescent atmosphere in which the gas has a line-of-sight velocity dispersion of 164 ± 10 kilometres per second in the region 30–60 kiloparsecs from the central nucleus. A gradient in the line-of-sight velocity of 150 ± 70 kilometres per second is found across the 60-kiloparsec image of the cluster core. Turbulent pressure support in the gas is four per cent of the thermodynamic pressure, with large-scale shear at most doubling this estimate. We infer that a total cluster mass determined from hydrostatic equilibrium in a central region would require little correction for turbulent pressure.
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We acknowledge all the JAXA members who have contributed to the ASTRO-H (Hitomi) project. All US members gratefully acknowledge support through the NASA Science Mission Directorate. Stanford and SLAC members acknowledge support via DoE contract to SLAC National Accelerator Laboratory DE-AC3-76SF00515 and NASA grant NNX15AM19G. Part of this work was performed under the auspices of the US DoE by LLNL under contract DE-AC52-07NA27344 and also supported by NASA grants to LLNL. Support from the European Space Agency is gratefully acknowledged. French members acknowledge support from CNES, the Centre National d’Etudes Spatiales. SRON is supported by NWO, the Netherlands Organization for Scientific Research. The Swiss team acknowledges support of the Swiss Secretariat for Education, Research and Innovation SERI and ESA’s PRODEX programme. The Canadian Space Agency is acknowledged for the support of Canadian members. We acknowledge support from JSPS/MEXT KAKENHI grant numbers 15H02070, 15K05107, 23340071, 26109506, 24103002, 25400236, 25800119, 25400237, 25287042, 24540229, 25105516, 23540280, 25400235, 25247028, 26800095, 25400231, 25247028, 26220703, 24105007, 23340055, 15H00773, 23000004, 15H02090, 15K17610, 15H05438, 15H00785 and 24540232. H. Akamatsu acknowledges support of NWO via a Veni grant. M. Axelsson acknowledges a JSPS International Research Fellowship. C. Done acknowledges STFC funding under grant ST/L00075X/1. P. Gandhi acknowledges a JAXA International Top Young Fellowship and UK Science and Technology Funding Council (STFC) grant ST/J003697/2. H. Russell, A. C. Fabian and C. Pinto acknowledge support from ERC Advanced Grant Feedback 340442. We thank contributions by many companies, including, in particular, NEC, Mitsubishi Heavy Industries, Sumitomo Heavy Industries and Japan Aviation Electronics Industry. Finally, we acknowledge strong support from the following engineers. JAXA/ISAS: C. Baluta, N. Bando, A. Harayama, K. Hirose, K. Ishimura, N. Iwata, T. Kawano, S. Kawasaki, K. Minesugi, C. Natsukari, H. Ogawa, M. Ogawa, M. Ohta, T. Okazaki, S.-i. Sakai, Y. Shibano, M. Shida, T. Shimada, A. Wada, T. Yamada; JAXA/TKSC: A. Okamoto, Y. Sato, K. Shinozaki, H. Sugita; Chubu U: Y. Namba; Ehime U: K. Ogi; Kochi U of Technology: T. Kosaka; Miyazaki U: Y. Nishioka; Nagoya U: H. Nagano; NASA/GSFC: T. Bialas, K. Boyce, E. Canavan, M. DiPirro, M. Kimball, C. Masters, D. Mcguinness, J. Miko, T. Muench, J. Pontius, P. Shirron, C. Simmons, G. Sneiderman, T. Watanabe; Noqsi Aerospace Ltd: J. Doty; Stanford U/KIPAC: M. Asai, K. Gilmore; ESA (Netherlands): C. Jewell; SRON: D. Haas, M. Frericks, P. Laubert, P. Lowes; U of Geneva: P. Azzarello; CSA: A. Koujelev, F. Moroso.
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Journal of Low Temperature Physics (2018)