Nuclear Rings in Galaxies---A Kinematic Perspective

TL;DR

This study investigates the kinematic properties of nuclear rings in galaxies, revealing their circular, planar nature, and explores how ring size correlates with galaxy dynamics and bar strength.

Contribution

It provides the first detailed kinematic analysis linking nuclear ring properties to their resonant origins and host galaxy characteristics.

Findings

Nuclear rings exhibit regular, symmetric, and circular kinematics.

Ring size correlates with bar strength, with weaker bars allowing larger rings.

A relationship exists between ring compactness, width, and mass concentration.

Abstract

We combine DensePak integral field unit and TAURUS Fabry-Perot observations of 13 nuclear rings to show an interconnection between the kinematic properties of the rings and their resonant origin. The nuclear rings have regular and symmetric kinematics, and lack strong non-circular motions. This symmetry, coupled with a direct relationship between the position angles and ellipticities of the rings and those of their host galaxies, indicate the rings are in the same plane as the disc and are circular. From the rotation curves derived, we have estimated the compactness (v^2/r) up to the turnover radius, which is where the nuclear rings reside. We find that there is evidence of a correlation between compactness and ring width and size. Radially wide rings are less compact, and thus have lower mass concentration. The compactness increases as the ring width decreases. We also find that the nuclear ring size is dependent on the bar strength, with weaker bars allowing rings of any size to form.