Study of central light concentration in nearby galaxies

Abstract

We propose a novel technique to estimate the masses of super massive black holes (SMBHs) residing at the centres of massive galaxies in the nearby Universe using simple photometry. Aperture photometry using SEXTRACTOR is employed to determine the central intensity ratio (CIR) at the optical centre of the galaxy image for a sample of 49 nearby galaxies with SMBH mass estimations. We find that the CIR of ellipticals and classical bulges is strongly correlated with SMBH masses whereas pseudo bulges and ongoing mergers show significant scatter. Also, the CIR of low luminosity AGNs in the sample shows significant connection with the 5 GHz nuclear radio emission suggesting a stronger link between the former and the SMBH evolution in these galaxies. In addition, it is seen that various structural and dynamical properties of the SMBH host galaxies are correlated with the CIR making the latter an important parameter in galaxy evolution studies. Finally, we propose the CIR to be an efficient and simple tool not only to distinguish classical bulges from pseudo bulges but also to estimate the mass of the central SMBH.

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

“…This scenario is also supported in the present study as we find low values of central intensity ratios in strong bars. In the case of early-type systems, it was observed that low values of central intensity ratio suggest massive black holes in galactic centres (Aswathy & Ravikumar 2018). Thus, the CIR seems to possess the potential to play a crucial role in understanding the linked evolution of rings, bars and central AGNs.…”

“…The CIR for early-type galaxies is reported to be anti-correlated with the mass of the supermassive black holes (SMBH, Aswathy & Ravikumar 2018). It is closely related to various structural and dynamical properties of host galaxies.…”

Stellar systems following the R1/m luminosity law

“…The degree to which light or mass is centrally concentrated is an important diagnostic for galaxies. The importance is obvious when the many physical galaxy properties are considered that correlate with (different measures of) the galaxy light concentration, including total luminosity (Caon et al 1993;Graham et al 2001a), velocity dispersion (Graham et al 2001a), Mg/Fe abundance ratio (Vazdekis et al 2004), central supermassive black hole mass (Graham et al 2001b;Aswathy & Ravikumar 2018), cluster local density (Trujillo et al 2002b), and emission at radio and X-ray wavelengths (Pović et al 2009;Aswathy & Ravikumar 2018). This has inspired several teams to propose galaxy concentration as an important parameter in automated galaxy classification schemes (Doi et al 1993;Abraham et al 1994;Bershady et al 2000;Conselice 2003).…”

“…Contrary to other concentration indices (e.g. Trujillo et al 2001;Graham et al 2001a;Aswathy & Ravikumar 2018), it is based on the intrinsic 3D density distribution, rather than on the light distribution on the plane of the sky. In the past few years, the interest in the central light (or mass) concentration of galaxies has only increased, thanks to a number of scaling relations between the central 1 The use of this unit system has been strongly advocated by Heggie & Mathieu (1986), and as a result, these standard units have sometimes been called Heggie units.…”

“…concentration and other galactic parameters, including velocity dispersion, supermassive black hole mass, optical-to-X-ray flux ratio and nuclear radio emission (e.g. Graham et al 2001a,b;Pović et al 2009;Aswathy & Ravikumar 2018). If physical processes in the evolution of a galaxy affect the mass or light concentration in a galaxy, we would primarily expect correlations that involve concentration indices based on the intrinsic density.…”