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Halo Concentrations and the Fundamental Plane of Galaxy Clusters

Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
Physics and Astronomy Department, Michigan State University, East Lansing, MI 48824, USA
INAF, Osservatorio di Astrofisica e Scienza dello Spazio, via Pietro Gobetti 93/3, 40129 Bologna, Italy
INFN, Sezione di Bologna, viale Berti Pichat 6/2, I-40127 Bologna, Italy
Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan
INAF, Osservatorio Astronomico di Trieste, via Tiepolo 11, I-34131 Trieste, Italy
Department of Astrophysical Sciences, 4 Ivy Lane, Princeton, NJ 08544, USA
Department of Physical Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208, USA
Author to whom correspondence should be addressed.
Galaxies 2019, 7(1), 8;
Received: 25 October 2018 / Revised: 3 December 2018 / Accepted: 21 December 2018 / Published: 2 January 2019
(This article belongs to the Special Issue From Dark Haloes to Visible Galaxies)
According to the standard cold dark matter (CDM) cosmology, the structure of dark halos including those of galaxy clusters reflects their mass accretion history. Older clusters tend to be more concentrated than younger clusters. Their structure, represented by the characteristic radius r s and mass M s of the Navarro–Frenk–White (NFW) density profile, is related to their formation time. In this study, we showed that r s , M s , and the X-ray temperature of the intracluster medium (ICM), T X , form a thin plane in the space of ( log r s , log M s , log T X ) . This tight correlation indicates that the ICM temperature is also determined by the formation time of individual clusters. Numerical simulations showed that clusters move along the fundamental plane as they evolve. The plane and the cluster evolution within the plane could be explained by a similarity solution of structure formation of the universe. The angle of the plane shows that clusters have not achieved “virial equilibrium” in the sense that mass/size growth and pressure at the boundaries cannot be ignored. The distribution of clusters on the plane was related to the intrinsic scatter in the halo concentration–mass relation, which originated from the variety of cluster ages. The well-known mass–temperature relation of clusters ( M Δ T X 3 / 2 ) can be explained by the fundamental plane and the mass dependence of the halo concentration without the assumption of virial equilibrium. The fundamental plane could also be used for calibration of cluster masses. View Full-Text
Keywords: galaxies: clusters: general; cosmology: theory; dark matter; large-scale structure of Universe galaxies: clusters: general; cosmology: theory; dark matter; large-scale structure of Universe
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Fujita, Y.; Donahue, M.; Ettori, S.; Umetsu, K.; Rasia, E.; Meneghetti, M.; Medezinski, E.; Okabe, N.; Postman, M. Halo Concentrations and the Fundamental Plane of Galaxy Clusters. Galaxies 2019, 7, 8.

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