Kinematic alignment of non-interacting CALIFA galaxies: Quantifying the impact of bars on stellar and ionised gas velocity field orientations

TL;DR

This study analyzes the kinematic orientations of non-interacting CALIFA galaxies to understand how internal structures like bars influence velocity fields, providing a baseline for detecting external distortions.

Contribution

It offers a detailed comparison of stellar and gas kinematic position angles in isolated galaxies, highlighting the stability of kinematic orientations despite internal features.

Findings

Morpho-kinematic differences are less than 22 degrees in 90% of the sample.

Internal kinematic misalignments are generally smaller than 16 degrees.

Stellar and gas kinematic PAs are tightly correlated across different galaxy features.

Abstract

We present 80 stellar and ionised gas velocity maps from the Calar Alto Legacy Integral Field Area (CALIFA) survey in order to characterize the kinematic orientation of non-interacting galaxies. The study of galaxies in isolation is a key step towards understanding how fast-external processes, such as major mergers, affect kinematic properties in galaxies. We derived the global and individual (projected approaching and receding sides) kinematic position angles (PAs) for both the stellar and ionised gas line-of-sight velocity distributions. When compared to the photometric PA, we find that morpho-kinematic differences are smaller than 22 degrees in 90% of the sample for both components; internal kinematic misalignments are generally smaller than 16 degrees. We find a tight relation between the global stellar and ionised gas kinematic PA consistent with circular-flow pattern motions in both components. This relation also holds generally in barred galaxies across the bar and galaxy disk scales. Our findings suggest that even in the presence of strong bars, both the stellar and the gaseous components tend to follow the gravitational potential of the disk. As a result, kinematic orientation can be used to assess the degree of external distortions in interacting galaxies.