  Recently X-ray observations have shown the common presence of compact
galactic coronae around intermediate-mass spheroid galaxies embedded in the
intracluster/intragroup medium (ICM). We conduct 2-D hydrodynamic simulations
to study the quasi-steady-state properties of such coronae as the natural
products of the ongoing distributed stellar feedback semi-confined by the
thermal and ram pressures of the ICM. We find that the temperature of a
simulated corona depends primarily on the specific energy of the feedback,
consistent with the lack of the correlation between the observed hot gas
temperature and K-band luminosity of galaxies. The simulated coronae typically
represent subsonic outflows, chiefly because of the semi-confinement. As a
result, the hot gas density increases with the ICM thermal pressure. The ram
pressure, on the other hand, chiefly affects the size and lopsidedness of the
coronae. The density increase could lead to the compression of cool gas clouds,
if present, and hence the formation of stars. The increase also enhances
radiative cooling of the hot gas, which may fuel central supermassive black
holes, explaining the higher frequency of active galactic nuclei observed in
clusters than in the field. The radiation enhancement is consistent with a
substantially higher surface brightness of the X-ray emission detected from
coronae in cluster environment. The total X-ray luminosity of a corona,
however, depends on the relative importance of the surrounding thermal and ram
pressures. These environment dependences should at least partly explain the
large dispersion in the observed diffuse X-ray luminosities of spheroids with
similar stellar properties. Furthermore, we show that an outflow powered by the
distributed feedback can naturally produce a positive radial gradient in the
hot gas entropy, mimicking a cooling flow.

High Energy Astrophysical Phenomena