The Circum-Galactic Medium of MASsive Spirals II: Probing the Nature of
  Hot Gaseous Halo around the Most Massive Isolated Spiral Galaxies
  We present the analysis of the XMM-Newton data of the Circum-Galactic Medium
of MASsive Spirals (CGM-MASS) sample of six extremely massive spiral galaxies
in the local Universe. All the CGM-MASS galaxies have diffuse X-ray emission
from hot gas detected above the background extending $\sim(30-100)\rm~kpc$ from
the galactic center. This doubles the existing detection of such extended hot
CGM around massive spiral galaxies. The radial soft X-ray intensity profile of
hot gas can be fitted with a $\beta$-function with the slope typically in the
range of $\beta=0.35-0.55$. This range, as well as those $\beta$ values
measured for other massive spiral galaxies, including the Milky Way (MW), are
in general consistent with X-ray luminous elliptical galaxies of similar hot
gas luminosity and temperature, and with those predicted from a hydrostatic
isothermal gaseous halo. Hot gas in such massive spiral galaxy tends to have
temperature comparable to its virial value, indicating the importance of
gravitational heating. This is in contrast to lower mass galaxies where hot gas
temperature tends to be systematically higher than the virial one. The ratio of
the radiative cooling to free fall timescales of hot gas is much larger than
the critical value of $\sim10$ throughout the entire halos of all the CGM-MASS
galaxies, indicating the inefficiency of gas cooling and precipitation in the
CGM. The hot CGM in these massive spiral galaxies is thus most likely in a
hydrostatic state, with the feedback material mixed with the CGM, instead of
escaping out of the halo or falling back to the disk. We also homogenize and
compare the halo X-ray luminosity measured for the CGM-MASS galaxies and other
galaxy samples and discuss the "missing" galactic feedback detected in these
massive spiral galaxies.
