Magnetically Confined Interstellar Hot Plasma in the Nuclear Bulge of
  our Galaxy
  The origin of the Galactic center diffuse X-ray emission (GCDX) is still
under intense investigation. In particular, the interpretation of the hot (kT ~
7 keV) component of the GCDX, characterised by the strong Fe 6.7 keV line
emission, has been contentious. If the hot component originates from a truly
diffuse interstellar plasma, not a collection of unresolved point sources, such
plasma cannot be gravitationally bound, and its regeneration would require a
huge amount of energy. Here we show that the spatial distribution of the GCDX
does NOT correlate with the number density distribution of an old stellar
population traced by near-infrared light, strongly suggesting a significant
contribution of the diffuse interstellar plasma. Contributions of the old
stellar population to the GCDX are implied to be about 50 % and 20 % in the
Nuclear stellar disk and Nuclear star cluster, respectively. For the Nuclear
stellar disk, a scale height of 0.32 +- 0.02 deg is obtained for the first time
from the stellar number density profiles. We also show the results of the
extended near-infrared polarimetric observations in the central 3 deg * 2 deg
region of our Galaxy, and confirm that the GCDX region is permeated by a large
scale, toroidal magnetic field as previously claimed. Together with observed
magnetic field strengths close to energy equipartition, the hot plasma could be
magnetically confined, reducing the amount of energy required to sustain it.
