JVLA Observations of IC342: Probing Star Formation in the Nucleus
  IC342 is a nearby, late-type spiral galaxy with a young nuclear star cluster
surrounded by several giant molecular clouds. The IC342 nuclear region is
similar to the Milky Way and therefore provides an interesting comparison. We
explore star formation in the nucleus using radio recombination line (RRL) and
continuum emission at 5, 6.7, 33, and 35 GHz with the JVLA. These radio tracers
are largely unaffected by dust and therefore sensitive to all of the thermal
emission from the ionized gas produced by early-type stars. We resolve two
components in the RRL and continuum emission within the nuclear region that lie
east and west of the central star cluster. These components are associated both
spatially and kinematically with two giant molecular clouds. We model these
regions in two ways: a simple model consisting of uniform gas radiating in
spontaneous emission, or as a collection of many compact HII regions in
non-LTE. The multiple HII region model provides a better fit to the data and
predicts many dense (ne ~ 10^4-10^5 cm-3), compact (< 0.1 pc) HII regions. For
the whole nuclear region as defined by RRL emission, we estimate a hydrogen
ionizing rate of NL ~ 2 x 10^{52} s^{-1}, corresponding to equivalent ~ 2000 O6
stars and a star formation rate of ~ 0.15 Msun/year. We detect radio continuum
emission west of the southern molecular mini spiral arm, consistent with
trailing spiral arms.
