SOFIA/FORCAST Imaging of the Circumnuclear Ring at the Galactic Center
  We present 19.7, 31.5, and 37.1 {\mu}m images of the inner 6 pc of the
Galactic Center of the Milky Way with a spatial resolution of 3.2 - 4.6'' taken
by the Faint Object Infrared Camera on the Stratospheric Observatory for
Infrared Astronomy (SOFIA). The images reveal in detail the "clumpy" structure
of the Circumnuclear Ring (CNR)--the torus of hot gas and dust orbiting the
supermassive black hole at the Galactic Center with an inner radius of 1.4 pc.
The CNR exhibits features of a classic HII region: the dust emission at 19.7
{\mu}m closely traces the ionized gas emission observed in the radio while the
31.5 and 37.1 {\mu}m emission traces the photo-dissociation region beyond the
ionized gas. The 19.7/37.1 color temperature map reveals a radial temperature
gradient across the CNR with temperatures ranging from 65-85 K, consistent with
the prevailing paradigm in which the dust is centrally heated by the inner
cluster of hot, young stars. We produce a 37.1 {\mu}m intensity model of the
CNR with the derived geometric properties and find that it is consistent with
the observed 37.1 {\mu}m map of the CNR. Dense ($5 to 9 \times 10^{4} \,
\mathrm{cm}^{-3}$) clumps with a FWHM of ~0.15 pc exist along the inner edge of
the CNR and shadow the material deeper into the ring. The clumps are unlikely
to be long-lived structures since they are not dense enough to be stable
against tidal shear from the supermassive black hole.
