Co-evolution of Nuclear Rings, Bars and the Central Intensity Ratio of
  their Host Galaxies
  Using a sample of 13 early-type spiral galaxies hosting nuclear rings, we
report remarkable correlations between the properties of the nuclear rings and
the central intensity ratio (CIR) of their host galaxies. The CIR, a function
of intensity of light within the central 1.5 and 3 arcsec region, is found to
be a vital parameter in galaxy evolution, as it shares strong correlations with
many structural and dynamical properties of early-type galaxies, including mass
of the central supermassive black hole (SMBH). We use archival HST images for
aperture photometry at the centre of the galaxy image to compute the CIR. We
observe that the relative sizes of nuclear rings and ring cluster surface
densities strongly correlate with the CIR. These correlations suggest reduced
star formation in the centres of galaxies hosting small and dense nuclear
rings. This scenario appears to be a consequence of strong bars as advocated by
the significant connection observed between the CIR and bar strengths. In
addition, we observe that the CIR is closely related with the integrated
properties of the stellar population in the nuclear rings associating the rings
hosting older and less massive star clusters with low values of CIR. Thus, the
CIR can serve as a crucial parameter in unfolding the coupled evolution of bars
and rings as it is intimately connected with both their properties.
