  Based mainly on X-ray observations, studies are made on interactions between
the intra-cluster medium (ICM) in clusters of galaxies and their member
galaxies. Through (magneto)hydrodynamic and gravitational channels, the moving
galaxies are expected to drag the ICM around them, and transfer to the ICM some
fraction of their dynamical energies on cosmological time scales. This
hypothesis is in line with several observations, including the possible
cosmological infall of galaxies towards the cluster center, found over
redshifts of z~1 to z~0. Further assuming that the energy lost by the galaxies
is first converted into ICM turbulence and then dissipated, this picture can
explain the subsonic and uniform ICM turbulence, measured with Hitomi in the
core region of the Perseus cluster. The scenario may also explain several other
unanswered problems regarding clusters of galaxies, including what prevents the
ICM from the expected radiative cooling, how the various mass components in
nearby clusters have attained different radial distributions, and how a thermal
stability is realized between hot and cool ICM components that co-exist around
cD galaxies. This view is also considered to pertain to the general scenario of
galaxy evolution, including their environmental effects.
