Counter-rotating disks in galaxies: dissecting kinematics and stellar populations with 3D spectroscopy

TL;DR

This paper introduces a spectral decomposition method to analyze the kinematics and stellar populations of galaxies with counter-rotating disks, revealing that these disks are typically less massive, younger, and chemically distinct from the main galaxy disk.

Contribution

The paper presents a novel spectral decomposition technique that isolates different kinematic components in galaxies, enabling detailed study of their stellar populations and properties.

Findings

Counter-rotating disks are less massive than main disks.

Counter-rotating disks are younger than main disks.

Counter-rotating disks have distinct chemical compositions.

Abstract

We present a spectral decomposition technique that separates the contribution of different kinematic components in galaxies from the observed spectrum. This allows to study the kinematics and properties of the stellar populations of the individual components (e.g., bulge, disk, counter-rotating cores, orthogonal structures). Here, we discuss the results of this technique for galaxies that host counter-rotating stellar disks of comparable size. In all the studied cases, the counter-rotating stellar disk is the less massive, the youngest and has different chemical content (metallicity and alpha-elements abundance ratio) than the main galaxy disk. Further applications of the spectral decomposition technique are also discussed.