Fueling AGN-I: How the Global Characteristics of the Central Kiloparsec of Seyferts differ from Quiescent Galaxies

TL;DR

This study compares the central kiloparsec regions of Seyfert and quiescent galaxies, revealing that Seyferts have a dynamically cold nuclear structure with concentrated gas and young stars, linked to AGN fueling.

Contribution

It provides the first comparative analysis of global nuclear characteristics in Seyfert versus quiescent galaxies, highlighting features associated with AGN activity.

Findings

Seyferts have more centrally concentrated stellar brightness within 100 pc.

Seyferts exhibit lower stellar velocity dispersion within 200 pc.

Seyferts show elevated H2 luminosity out to at least 250 pc.

Abstract

In a matched sample of Seyfert and quiescent galaxies we simultaneously probe the stellar and molecular gas kinematics from 1 kpc down to 50 pc with the aim of identifying the dynamical processes dictating black hole accretion rates. This first paper compares the global characteristics of a sample of ten galaxies. We find several differences within a radius of 500 pc that are correlated with Active Galactic Nucleus (AGN) activity. The Seyferts have: (1) a more centrally concentrated nuclear stellar surface brightness with lower stellar luminosities beyond a radius of 100 pc, (2) a lower stellar velocity dispersion within a radius of 200 pc, (3) elevated H2 luminosity out to a radius of at least 250 pc, and (4) more centrally concentrated H2 surface brightness profiles. These observed differences can be interpreted as evidence for Seyfert galaxies having a dynamically cold (in comparison to the bulge) nuclear structure composed of a significant gas reservoir and a relatively young stellar population. This structure is undetected (and possibly does not exist) in quiescent galaxies. The presence of such a nuclear structure in Seyfert galaxies provides evidence for inflow of the surrounding interstellar medium since the nuclear stellar population requires a supply of gas from which to form. The fueling of a Seyfert AGN is thus associated with the formation of a dynamically cold component of gas and stars on scales of hundreds of parsecs.