Effect of AGN on the morphological properties of their host galaxies in the local Universe

Abstract

ABSTRACT The morphological classification of active galaxies may be affected by the presence of active galactic nuclei (AGNs). In this paper, we provide the most detailed analysis on how different AGN contributions, from 5 per cent to 75 per cent, to the total optical light may affect six commonly used morphological parameters and the final classification of AGN host galaxies at z ∼ 0. We used a local sample of > 2000 visually classified non-active galaxies, to quantify how the contribution of a bright nuclear point source of different intensity could affect morphological parameters such as: asymmetry, Abraham concentration index, Gini, M20 moment of light, smoothness, and Conselice-Bershady concentration index. We found that most of the morphological parameters are affected by AGN contributions above 25 per cent, with late-type galaxies being more affected than early-types. We found that Gini, Abraham concentration index, and asymmetry are the most stable parameters even for AGN contributions above 25 per cent, in comparison to Conselice-Bershady concentration index and M20 moment of light. Smoothness parameter shall be avoided when classifying AGN host galaxies, or at least it shall be used simultaneously in combination with several other parameters.