Nonthermal Filamentary Radio Features Within 20 pc of the Galactic
  Center
  Deep imaging of the Sgr A complex at 6 cm wavelength with the B and C
configurations of the Karl G. Jansky VLA has revealed a new population of faint
radio filaments. Like their brighter counterparts that have been observed
throughout the Galactic Center on larger scales, these filaments can extend up
to ~10 parsecs, and in most cases are strikingly uniform in brightness and
curvature. Comparison with a survey of Paschen-alpha emission reveals that some
of the filaments are emitting thermally, but most of these structures are
nonthermal: local magnetic flux tubes illuminated by synchrotron emission. The
new image reveals considerable filamentary substructure in previously known
nonthermal filaments (NTFs). Unlike NTFs previously observed on larger scales,
which tend to show a predominant orientation roughly perpendicular to the
Galactic plane, the NTFs in the vicinity of the Sgr A complex are relatively
randomly oriented. Two well-known radio sources to the south of Sgr A - sources
E and F - consist of numerous quasi-parallel filaments that now appear to be
particularly bright portions of a much larger, strongly curved, continuous,
nonthermal radio structure that we refer to as the "Southern Curl". It is
therefore unlikely that sources E and F are HII regions or pulsar wind nebulae.
The Southern Curl has a smaller counterpart on the opposite side of the
Galactic Center - the Northern Curl - that, except for its smaller scale and
smaller distance from the center, is roughly point-reflection symmetric with
respect to the Southern Curl. The curl features indicate that some field lines
are strongly distorted, presumably by mass flows. The point symmetry about the
center then suggests that the flows originate near the center and are somewhat
collimated.
