Digging for red nuggets: discovery of hot halos surrounding massive,
  compact, relic galaxies
  We present the results of Chandra X-ray observations of the isolated,
massive, compact, relic galaxies MRK 1216 and PGC 032873. Compact massive
galaxies observed at z>2, also called red nuggets, formed in quick dissipative
events and later grew by dry mergers into the local giant ellipticals. Due to
the stochastic nature of mergers, a few of the primordial massive galaxies
avoided the mergers and remained untouched over cosmic time. We find that the
hot atmosphere surrounding MRK 1216 extends far beyond the stellar population
and has an 0.5-7 keV X-ray luminosity of $L_{\rm X}=(7.0\pm0.2)\times10^{41}$
erg s$^{-1}$, which is similar to the nearby X-ray bright giant ellipticals.
The hot gas has a short central cooling time of $\sim50$ Myr and the galaxy has
a $\sim13$ Gyr old stellar population. The presence of an X-ray atmosphere with
a short nominal cooling time and the lack of young stars indicate the presence
of a sustained heating source, which prevented star formation since the
dissipative origin of the galaxy 13 Gyrs ago. The central temperature peak and
the presence of radio emission in the core of the galaxy indicate that the
heating source is radio-mechanical AGN feedback. Given that both MRK 1216 and
PGC 032873 appear to have evolved in isolation, the order of magnitude
difference in their current X-ray luminosity could be traced back to a
difference in the ferocity of the AGN outbursts in these systems. Finally, we
discuss the potential connection between the presence of hot halos around such
massive galaxies and the growth of super/over-massive black holes via chaotic
cold accretion.
