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Turbulent heating in galaxy clusters brightest in X-rays


The hot (107 to 108 kelvin), X-ray-emitting intracluster medium (ICM) is the dominant baryonic constituent of clusters of galaxies. In the cores of many clusters, radiative energy losses from the ICM occur on timescales much shorter than the age of the system1,2,3. Unchecked, this cooling would lead to massive accumulations of cold gas and vigorous star formation4, in contradiction to observations5. Various sources of energy capable of compensating for these cooling losses have been proposed, the most promising being heating by the supermassive black holes in the central galaxies, through inflation of bubbles of relativistic plasma6,7,8,9. Regardless of the original source of energy, the question of how this energy is transferred to the ICM remains open. Here we present a plausible solution to this question based on deep X-ray data and a new data analysis method that enable us to evaluate directly the ICM heating rate from the dissipation of turbulence. We find that turbulent heating is sufficient to offset radiative cooling and indeed appears to balance it locally at each radius—it may therefore be the key element in resolving the gas cooling problem in cluster cores and, more universally, in the atmospheres of X-ray-emitting, gas-rich systems on scales from galaxy clusters to groups and elliptical galaxies.

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Figure 1: X-ray image of the core of the Perseus cluster.
Figure 2: Measured amplitude of the one-component velocity V1,k of gas motions versus wavenumber k.
Figure 3: Turbulent heating (Qheat) versus gas cooling (Qcool) rates in the Perseus and Virgo cores.


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Support for this work was provided by the NASA through Chandra award number AR4-15013X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the NASA under contract NAS8-03060. S.W.A. acknowledges support from the US Department of Energy under contract number DE-AC02-76SF00515. I.Z. and N.W. are partially supported from Suzaku grants NNX12AE05G and NNX13AI49G. P.A. acknowledges financial support from Fondecyt 1140304 and European Commission’s Framework Programme 7, through the Marie Curie International Research Staff Exchange Scheme LACEGAL (PIRSES-GA -2010-2692 64). E.C. and R.S. are partially supported by grant no. 14-22-00271 from the Russian Scientific Foundation.

Author information




I.Z.: data analysis, interpretation, manuscript preparation; E.C.: data analysis, interpretation, manuscript preparation; A.A.S.: interpretation, discussions, manuscript preparation; A.C.F.: principal investigator of the Perseus cluster observations, interpretation, manuscript review; S.W.A.: interpretation, discussions, manuscript review; W.R.F.: principal investigator of the M87 observations, interpretation, manuscript review; P.A., J.S.S., A.S., R.S., A.V., N.W.: interpretation, discussions and manuscript review.

Corresponding author

Correspondence to I. Zhuravleva.

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The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Thermodynamic properties of the Perseus and Virgo clusters.

Radial profiles of the deprojected electron number density, the electron temperature, the cooling (tcool) and free-fall (tff) times, and the sound speed. Red points: data with 1σ error bars; black curves: data approximations using smooth functions. The increased temperature scatter in the central few kiloparsecs is associated with the presence of multi-temperature plasma in cool cores. A two-temperature fit of high-resolution XMM-Newton RGS spectra of the core of Virgo suggests an ambient temperature there of 1.6 keV (ref. 54). The smooth-function approximation we have chosen therefore approaches this value.

Extended Data Figure 2 X-ray image of the core of the Virgo cluster.

a, X-ray surface brightness in units of counts per second per pixel in the 0.5–3.5 keV energy band. b, Relative surface brightness fluctuations. Both images are smoothed with a 3′′ Gaussian. Black circles: excised point sources and central jet. White circles indicate ‘arm-like’ structures associated with the central AGN’s activity, which have also been excised. We adopt 16.9 Mpc as the distance to the cluster, implying that an angular size of 1′ corresponds to a length scale of 4.91 kpc.

Extended Data Figure 3 Set of the radial annuli used in the analysis of the Perseus and Virgo clusters.

The same as Fig. 1b and Extended Data Fig. 1b with white circles indicating the annuli used. The width of each annulus is 1.5′ ≈ 31 kpc in Perseus (a) and 2′ ≈ 9.8 kpc in Virgo (b). The outermost circles are 10.5′ ≈ 218 kpc and 8′ ≈ 39 kpc in Perseus and Virgo, respectively.

Extended Data Figure 4 Turbulent heating per unit density versus radiative cooling per unit density, and the Ozmidov scale in the Perseus and Virgo clusters.

a, The same as Fig. 3, but with the turbulent heating and cooling rates divided by the mass density of gas in each annulus. b, The same as Fig. 2 with the Ozmidov scale lO = 1/kO = N3/2ε1/2 shown for each annulus (vertical black lines), estimated using ε = Qcool/ρ0 (assuming that Qturb = Qcool).

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Zhuravleva, I., Churazov, E., Schekochihin, A. et al. Turbulent heating in galaxy clusters brightest in X-rays. Nature 515, 85–87 (2014).

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