Increased Molecular Gas Velocity Dispersion and Star Formation Efficiency in Barred Galaxy Centres

Work by the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) collaboration found higher molecular gas surface densities and velocity dispersions in the centers of barred galaxies compared to unbarred galaxies. We explore central molecular gas using published high resolution (150 pc) measurements of CO(2–1) from the PHANGS-ALMA survey and a new velocity dispersion-dependent prescription for the CO-to-H2 conversion factor αCO. Comparisons of the molecular gas surface density, velocity dispersion, star formation rate, and depletion time reveal that these quantities are different in the centers of barred and unbarred galaxies. Gas depletion times are found to be shorter in barred galaxy centers. Even when we control for the presence of an active galactic nucleus, the velocity dispersion and depletion time are found to be statistically different between barred and unbarred galaxy centers. The higher velocity dispersion suggests extra noncircular motions, possibly due to the inflow of gas along the bar, that are not constant but must increase as the star formation rate increases.