On the Role of Noncircular Motions in MaNGA Galaxies. I. Global Properties

Noncircular (NC) motions represent the imprints of nonaxisymmetric structures in galaxies, providing opportunities to study the physical properties of gas departing from circular rotation. In this work, we have conducted a systematic study of the NC motions in a sample of 1624 gas-rich disk galaxies from the Mapping Nearby Galaxies at Apache Point Observatory (or MaNGA) Product Launch-11. By using the Hα velocity as a tracer of the disk rotation, we find indications that the amplitude of the NC motions is related to the stellar mass, with the low-mass and late-type galaxies the most affected. In our sample, we find ratios of NC to circular rotation ranging from 5% to 20%. By implementing harmonic models to include NC motions associated with spiral arms and stellar bars, we find that the rotational curves traced with Hα are barely affected by the NC motions induced by these structures. Consequently, in our sample, we do not find evidence that NC motions contribute to the scatter of the stellar Tully–Fisher relation. Our results suggest that NC motions might have a more localized effect in galaxies rather than a global one.