AGN contribution on the morphological parameters of their host galaxies up to intermediate redshifts of z~2

TL;DR

This study investigates how active galactic nuclei (AGN) influence the morphological parameters of their host galaxies up to redshift z~2, revealing the stability of certain parameters and implications for galaxy classification.

Contribution

It introduces a method to assess AGN impact on galaxy morphology parameters at intermediate redshifts using simulated flux contributions and evaluates parameter robustness.

Findings

Concentration parameters are significantly affected when AGN contribution exceeds 25% and magnitude is greater than 23.

The GINI coefficient remains the most stable morphological parameter against AGN contamination.

Combining CABR, CCON, and asymmetry yields the best classification of active galaxies at high redshift.

Abstract

The presence of Active Galaxy Nuclei (AGN) can affect the morphological classification of galaxies. This work aims to determine how the contribution of AGN affects the most used morphological parameters down to the redshift of z~2 in COSMOS-like conditions. We use a sample of > 2000 local non-active galaxies, with a well-known visual morphological classification, and add an AGN as an unresolved component that contributes to the total galaxy flux with 5%-75%. We moved all the galaxies to lower magnitudes (higher redshifts) to map the conditions in the COSMOS field, and we measured six morphological parameters. The greatest impact on morphology occurs when considering the combined effect of magnitude, redshift and AGN, with spiral galaxies being the most affected. In general, all the concentration parameters change significantly if the AGN contribution is > 25% and the magnitude > 23. We find that the GINI coefficient is the most stable in terms of AGN and magnitude/redshift, followed by the M20, Conselice-Bershady (CCON), and finally the Abraham (CABR) concentration indexes. We find that, when using morphological parameters, the combination of CABR, CCON and asymmetry is the most effective in classifying active galaxies at high-redshift, followed by the combination of CABR and GINI.