The Central Kiloparsec of Seyfert and Inactive Host Galaxies: a Comparison of Two-Dimensional Stellar and Gaseous Kinematics

TL;DR

This study compares the two-dimensional stellar and gaseous kinematics in the central kiloparsecs of Seyfert and inactive galaxies, revealing similar large-scale rotation but more disturbed nuclear gas motions in Seyferts, hinting at a connection to nuclear activity.

Contribution

It provides the first detailed two-dimensional kinematic comparison of stars and gas in the central regions of matched Seyfert and inactive galaxies, highlighting differences at small scales.

Findings

Stellar kinematics show regular rotation aligned with galaxy axes.

Gas kinematics are mostly rotation-dominated and aligned with stars.

Nuclear gas motions are more disturbed in Seyfert galaxies.

Abstract

We investigate the properties of the two-dimensional distribution and kinematics of ionised gas and stars in the central kiloparsecs of a matched sample of nearby active (Seyfert) and inactive galaxies, using the SAURON Integral Field Unit on the William Herschel Telescope. The ionised gas distributions show a range of low excitation regions such as star formation rings in Seyferts and inactive galaxies, and high excitation regions related to photoionisation by the AGN. The stellar kinematics of all galaxies in the sample show regular rotation patterns typical of disc-like systems, with kinematic axes which are well aligned with those derived from the outer photometry and which provide a reliable representation of the galactic line of nodes. After removal of the non-gravitational components due to e.g. AGN-driven outflows, the ionised gas kinematics in both the Seyfert and inactive galaxies are also dominated by rotation with global alignment between stars and gas in most galaxies. This result is consistent with previous findings from photometric studies that the large-scale light distribution of Seyfert hosts are similar to inactive hosts. However, fully exploiting the two-dimensional nature of our spectroscopic data, deviations from axisymmetric rotation in the gaseous velocity fields are identified that suggest the gaseous kinematics are more disturbed at small radii in the Seyfert galaxies compared with the inactive galaxies, providing a tentative link between nuclear gaseous streaming and nuclear activity.