Astronomy and Astrophysics, volume 305, 407-420 (1996/1-2)
Turbulent mixing and excitation of density fluctuations in the intracluster medium.
DEISS B.M. and JUST A.
Abstract (from CDS):
Heating of the intracluster medium (ICM) by the gravitational drag of cluster galaxies has been discussed in the literature rather extensively (e.g Miller 1986; Just et al. 1990). However, excitation of density fluctuations and turbulent mixing of the gas accompanying the mechanism of galaxy stirring has not been treated in any great detail in the literature. In the present work we derive consistent (analytical) expressions for the amplitudes of velocity and density fluctuations, for the two-point correlation function and the corresponding correlation length, for the turbulent mixing time scale and for the heating rate of the cluster gas. To this end, we treat the gravitational interaction between galaxies and ICM by fluctuation theory. The system of galaxies is treated as a collisionless system, while the ICM is described hydrodynamically by a hot nonpolytropic gas; we also take into account the influence of a cosmic-ray component. Application to the Coma cluster (Abell 1656) and to the Perseus cluster (Abell 426) yields velocity fluctuations of the order of several hundred km/s, relative density fluctuations of about 50 percent, and turbulent mixing time scales of a few 109yrs. The results show that the exitation of fluctuations of the ICM by the galaxy stirring mechanism may be essential, e.g., for the structure of cooling flows, for the mixing of heavy elements within the ICM, and for the formation of extended radio halos observed in some clusters of galaxies.
hydrodynamics - turbulence - cooling flows - intergalactic medium - galaxies: kinematics and dynamics