Using 3D high-resolution hydrodynamic simulations, tracking both electrons and ions, we study the effects of turbulence and conduction in the hot intracluster medium. We show how the power spectrum of the gas density perturbations can accurately constrain both processes. The characteristic amplitude of density perturbations is linearly related to the strength of turbulence, i.e. the 3D Mach number, as A(k)_max = 0.25 M. The slope of A(k) in turn reflects the level of conduction. In a non-conductive medium, subsonic stirring motions advect density with a similar nearly Kolmogorov cascade. Increasing conduction (via magnetic suppression f = 0.001-1) progressively steepens the spectrum towards the Burgers-like regime. The turbulent Prandtl number defines the dynamic similarity of the flow; at scales where Pt < 100, the spectrum develops a significant decay. The transition is gentle for highly suppressed conduction, f < 0.001, while sharp in the opposite regime. For strong conductivity (f > 0.1), Pt ~ 100 occurs on spatial scales larger than the injection scale. The velocity spectrum is instead not much affected by conduction. The f > 0.1 regime affects the appearance of X-ray images, in which Kelvin-Helmholtz and Rayleigh-Taylor rolls and filaments are washed out. In a stratified system, weak/strong turbulence induces higher isobaric/adiabatic fluctuations, while conduction forces both modes towards the intermediate isothermal regime. We provide a general analytic fit which is applied to new deep Chandra observations of Coma. The observed spectrum is best consistent with strongly suppressed effective isotropic conduction, f = 0.001, and mild subsonic turbulence, M = 0.45 (with injection at ~250 kpc). The low conductivity corroborates the survival of sharp features in the ICM (cold fronts, filaments, bubbles), and indicates that cooling flows may not be balanced by conduction.
The Evaporation and Survival of Cluster Galaxies' Coronae Part II: The Effectiveness of Anisotropic Thermal Conduction and Survival of Stripped Galactic Tails
Constraining Effective Viscosity in the Intracluster Medium via the Thermal Sunyaev-Zeldovich Effect -- Predictions from the SLOW Constrained Coma Cluster Simulations
Ludwig-Maximilians-Universität München（慕尼黑大学）；University of Massachusetts, Amherst（马萨诸塞大学阿默斯特分校）；Univ. Lille, CNRS, Centrale Lille, UMR 9189 CRIStAL（里尔大学，法国国家科学研究中心，里尔中央理工学院，CRIStAL实验室）；Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale（巴黎萨克雷大学，法国国家科学研究中心，空间天体物理研究所）；Center for Astrophysics | Harvard & Smithsonian（哈佛史密松天体物理中心）；Max-Planck-Institut für Astrophysik（马克斯·普朗克天体物理学研究所）
