Volume 621, January 2019
|Number of page(s)||11|
|Section||Cosmology (including clusters of galaxies)|
|Published online||03 January 2019|
Non-thermal pressure support in X-COP galaxy clusters
1 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
2 Dipartimento di Fisica e Astronomia Università di Bologna, Via Piero Gobetti, 93/2, 40129 Bologna, Italy
3 INAF, Osservatorio di Astrofisica e Scienza dello Spazio, Via Pietro Gobetti 93/3, 40129 Bologna, Italy
4 INFN, Sezione di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
5 INAF, Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34131 Trieste, Italy
6 Dipartimento di Fisica dell’Università di Trieste, Sezione di Astromia, Via Tiepolo 11, 34131 Trieste, Italy
7 IRAP, Université de Toulouse, CNRS, CNES, UPS, Toulouse, France
8 INAF – IASF Milano, Via E. Bassini 15, 20133 Milano, Italy
9 Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 40131 Hamburg, Germany
10 Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ, 08544-1001, USA
11 INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy
12 Dipartimento di Fisica, Università degli Studi di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Roma, Italy
13 Center for Astronomy, Institute for Theoretical Astrophysics, Heidelberg University, Philosophenweg 12, 69120 Heidelberg, Germany
Accepted: 4 October 2018
Galaxy clusters are the endpoints of structure formation and are continuously growing through the merging and accretion of smaller structures. Numerical simulations predict that a fraction of their energy content is not yet thermalized, mainly in the form of kinetic motions (turbulence, bulk motions). Measuring the level of non-thermal pressure support is necessary to understand the processes leading to the virialization of the gas within the potential well of the main halo and to calibrate the biases in hydrostatic mass estimates. We present high-quality measurements of hydrostatic masses and intracluster gas fraction out to the virial radius for a sample of 13 nearby clusters with available XMM-Newton and Planck data. We compare our hydrostatic gas fractions with the expected universal gas fraction to constrain the level of non-thermal pressure support. We find that hydrostatic masses require little correction and infer a median non-thermal pressure fraction of ∼6% and ∼10% at R500 and R200, respectively. Our values are lower than the expectations of hydrodynamical simulations, possibly implying a faster thermalization of the gas. If instead we use the mass calibration adopted by the Planck team, we find that the gas fraction of massive local systems implies a mass bias 1 − b = 0.85 ± 0.05 for Sunyaev–Zeldovich-derived masses, with some evidence for a mass-dependent bias. Conversely, the high bias required to match Planck cosmic microwave background and cluster count cosmology is excluded by the data at high significance, unless the most massive halos are missing a substantial fraction of their baryons.
Key words: X-rays: galaxies: clusters / large-scale structure of Universe / galaxies: clusters: intracluster medium / galaxies: clusters: general
© ESO 2019
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