GMRT observations of NGC 2997 and radio detection of the circumnuclear
  ring
  We present high-resolution, high-sensitivity radio continuum observations of
the nearby spiral galaxy NGC 2997 at 332, 616 and 1272 MHz using the Giant
Metrewave Radio Telescope (GMRT). The integrated spectrum of this galaxy has a
spectral index of -0.92 ($S_{\nu}\propto\nu^{\alpha}$) and we place an upper
limit to the thermal fraction at 1272 MHz of ~ 10 per cent. Our multi-frequency
study shows a relatively flat spectrum source ($\alpha$ ~ -0.6) at the centre
of the galaxy. This leads to radio detection of a circumnuclear ring in the
high resolution map at 1272 MHz. We detect five hotspots in the ring, with
average star formation rate of ~ 0.024 $M_{\odot}\,yr^{-1}$, a median SN rate
of ~ 0.001 $yr^{-1}$ and luminosity of $10^{20}$ W Hz$^{-1}$. We estimate an
equipartition field in the central nuclear region of diameter ~ 750 pc to be
about $30\,\mu$G. We also report several interesting features along the spiral
arms. In this paper, we present the low frequency radio continuum maps, the
spectral index distribution, the circumnuclear ring and the derived physical
properties.
