$\Omega_{\rm bar}$ in NGC 5597 from VLA HI 21 cm Observations

TL;DR

This study measures the pattern speed of the stellar bar in NGC 5597 using VLA HI 21 cm observations, finding it consistent with values in similar barred galaxies and identifying resonance locations.

Contribution

First measurement of the bar's pattern speed in NGC 5597 using radio observations and the resonance method, linking it to galaxy resonance structures.

Findings

Pattern speed $ ightarrow$ 15.3 km/s/kpc

Resonance location at 6.73 kpc near spiral structure

Pattern speed similar to other barred galaxies

Abstract

We report Very Large Array B-configuration observations of the atomic hydrogen 21 cm line emission from the barred disk galaxy NGC 5597 at an angular resolution of 7.1" x 4.2". Using the resonance method, and assuming the ratio of the corotation radius to the semi-major axis of the stellar bar is unity ($\mathcal{R} \equiv R_{\rm CR}/a_{\rm bar} = 1$), we estimate the angular pattern speed of the stellar bar to be, $\Omega_{{\rm bar}} \sim 15.3$ km s$^{-1}$ kpc$^{-1}$. This constant value for $\Omega_{\rm bar}$ crosses $\Omega_{\rm gas} + \kappa(R)/4$ at a distance $\sim 6.73$ kpc which would correspond to the spatial location of the north spiral structure near an outer m=4 resonance. This value of $\Omega_{\rm bar}$ is similar to the values estimated for other bright nearby barred galaxies that exhibit circumnuclear rings (near ILR) or outer rings (near OLR).