Shape of LOSVD\lowercase{s} in barred disks: Implications for future IFU surveys

TL;DR

This study investigates how the skewness of line-of-sight velocity distributions (LOSVDs) in barred disk galaxies varies with viewing angle and bar structure, providing insights for future integral field unit (IFU) surveys.

Contribution

It offers new analysis of LOSVD skewness correlations in simulated barred galaxies at different inclinations, highlighting their potential as kinematic indicators for bars and bulges.

Findings

Anticorrelations in disk regions at certain inclinations.

Positive correlations in bar regions when viewed edge-on.

Variation of h_3 with viewing angle and bar structure.

Abstract

The shape of LOSVDs (line-of-sight velocity distributions) carries important information about the internal dynamics of galaxies. The skewness of LOSVDs represents their asymmetric deviation from a Gaussian profile. Correlations between the skewness parameter ($h_3$) and the mean velocity (\vm) of a Gauss-Hermite series reflect the underlying stellar orbital configurations of different morphological components. Using two self-consistent $N$-body simulations of disk galaxies with different bar strengths, we investigate \hv\ correlations at different inclination angles. Similar to previous studies, we find anticorrelations in the disk area, and positive correlations in the bar area when viewed edge-on. However, at intermediate inclinations, the outer parts of bars exhibit anticorrelations, while the core areas dominated by the boxy/peanut-shaped (B/PS) bulges still maintain weak positive correlations. When viewed edge-on, particles in the foreground/background disk (the wing region) in the bar area constitute the main velocity peak, whereas the particles in the bar contribute to the high-velocity tail, generating the \hv\ correlation. If we remove the wing particles, the LOSVDs of the particles in the outer part of the bar only exhibit a low-velocity tail, resulting in a negative \hv\ correlation, whereas the core areas in the central region still show weakly positive correlations. We discuss implications for IFU observations on bars, and show that the variation of the \hv\ correlation in the disk galaxy may be used as a kinematic indicator of the bar and the B/PS bulge.