Investigating the Core Morphology-Seyfert Class relationship with Hubble Space Telescope Archival Images of local Seyfert galaxies

TL;DR

This study investigates the relationship between core galaxy morphology and Seyfert class in local AGN using Hubble Space Telescope images, combining visual and automated methods to analyze dust features and morphology correlations.

Contribution

It re-establishes the core morphology-Seyfert class relationship with HST data and introduces an automated technique for dust feature detection in AGN cores.

Findings

Sy2 galaxies tend to have more dust features than Sy1.

No strong correlation between dust morphology and Seyfert class was found.

Automated methods can effectively classify core dust features in AGN images.

Abstract

The Unified Model of Active Galactic Nuclei (AGN) has provided a successful explanation for the observed diversity of AGN in the local Universe. However, recent analysis of multi-wavelength spectral and image data suggests that the Unified Model is only a partial theory of AGN, and may need to be augmented to remain consistent with all observations. Recent studies using high spatial resolution ground- and space-based observations of local AGN show that Seyfert class and the "core" (r<~1 kpc) host-galaxy morphology are correlated. Currently, this relationship has only been established qualitatively, by visual inspection of the core morphologies of low redshift (z<0.035) Seyfert host galaxies (Malkan et al. 1998). We re-establish this empirical relationship in Hubble Space Telescope (HST) optical imaging by visual inspection of a catalog of 85 local (D<63 Mpc) Seyfert galaxies. We also attempt to re-establish the core morphology-Seyfert class relationship using an automated, non-parametric technique that combines both existing classification parameters methods (the adapted CAS, G-M20), and a new method which implements the Source Extractor software for feature detection in unsharp-mask images. This new method is designed explicitly to detect dust features in the images. We use our automated approach to classify the morphology of the AGN cores and determine that Sy2 galaxies visually appear, on average, to have more dust features than Sy1. With the exception of this "dustiness" however, we do not measure a strong correlation between the dust morphology and the Seyfert class of the host galaxy using quantitative techniques. We discuss the implications of these results in the context of the Unified Model.