Co-evolution of nuclear rings, bars and the central intensity ratio of their host galaxies

Abstract

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.

Study of Central Intensity Ratio of Seyfert Galaxies in Nearby Universe

“…The Central Intensity Ratio (CIR), a new photometric parameter, is well correlated with the masses of central SMBHs of the spheroid of early-type galaxies (ETGs, Aswathy & Ravikumar 2018). Furthermore, CIR is an efficient photometric tool to study the central and structural properties of spiral galaxies, especially barred systems, and also gives some valid information regarding nuclear star formation and AGN formalism in host galaxies (Aswathy & Ravikumar 2020). In this light, we perform an optical analysis by utilizing the parameter, CIR, to study the central properties and evolution of Seyfert galaxies.…”

Study of central intensity ratio of early-type galaxies from low density environment

“…Also they reported significant correlations between CIR and various parameters of the SMBH hosting galaxies such as age, stellar mass and central radio emission from low luminosity AGNs. Aswathy & Ravikumar (2020) reported remarkable correlations between properties of nuclear rings and CIR of their host galaxies using a sample of 13 early-type spiral galaxies, suggested use of CIR as a tool to explore co-evolution between various structural and dynamical properties of galaxies. Table 1 shows properties of sample galaxies along with CIR and associated uncertainties.…”

Study of central light distribution in nearby early-type galaxies hosting nuclear star clusters

“…The various correlations shown by CIR in field early-type galaxies (hereafter ETGs) (Sruthi & Ravikumar 2021) explored the co-evolution scenario in galaxies. The CIR is also found to contain information about the star formation near the central region of galaxies (Aswathy & Ravikumar 2020). Therefore, the CIR can be used as an ideal tool in studying galaxies hosting NSCs.…”