Recent results indicate a correlation between nuclear radio-loudness of active galaxies and their central stellar surface-brightness profiles , in that ‘ core ’ galaxies ( with inner logarithmic slope \gamma \leq 0.3 ) are significantly more radio loud than ‘ power-law ’ galaxies ( \gamma \geq 0.5 ) .
This connection , which indicates possible links between radio-loudness and galaxy formation history ( e.g .
through black hole spin ) has so far only been confirmed for a radio-selected sample of galaxies .
Furthermore , it has since been shown that the Nuker law , which was used to parameterise the brightness profiles in these studies , gives a poor description of the brightness profile , with its parameters varying systematically with the radial fitted extent of the profile .
Here , we present an analysis of the central surface brightness profiles of the active galaxies of Hubble Type T \leq 3 , that were identified by the optically-selected Palomar spectroscopic survey of nearby galaxies .
We fit the brightness profiles using Sérsic , Core-Sérsic and , where necessary , Double-Sérsic models , which we fit to the semi-major axis brightness profiles extracted from high resolution images of the galaxies from the Hubble Space Telescope ( HST ) .
We use these fits to classify the galaxies as ‘ Core ’ , ‘ Sérsic ’ or ‘ Double-Sérsic ’ .
We compare the properties of the Active Galactic Nuclei ( AGNs ) and their host galaxies with this classification , and we recover the already established trend for Core galaxies to be more luminous and contain a higher-mass supermassive black hole .
Defining the radio-loudness of an AGN as the ratio of the nuclear radio luminosity to [ O iii ] line luminosity , which allows us to include most of the AGN in our sample and prevents a bias against dim nuclei that are harder to extract from the brightness profiles , we find that AGN hosted in Core galaxies are generally more radio-loud than those hosted in Sérsic galaxies , although there is a large overlap between the two subsamples .
The correlation between radio-loudness and brightness profile can partly be explained by a correlation between radio-loudness and black hole mass .
Additionally , there is a significant ( 99 per cent confidence ) partial correlation between radio-loudness and the Core/Sérsic classification of the host galaxy , which lends support to the previous results based on the radio-selected sample , although it is possible that this partial correlation arises because AGN in core galaxies tend to have a lower accretion rate as well as a higher central black hole mass .