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

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).