Discovery of a new population of galactic H II regions with ionized gas velocity gradients

We investigate the kinematic properties of Galactic H II regions using radio recombination line (RRL) emission detected by the Australia Telescope Compact Array at 4-10 GHz and the Jansky Very Large Array at 8-10 GHz. Our H II region sample consists of 425 independent observations of 374 nebulae that are relatively well isolated from other, potentially confusing sources and have a single RRL component with a high signal-to-noise ratio. We perform Gaussian fits to the RRL emission in position-position-velocity data cubes and discover velocity gradients in 178 (42%) of the nebulae with magnitudes between 5 and 200 m s(-1)arcsec(-1) II region simulations that include bipolar outflows or solid body rotational motions to explain the observed velocity gradients. The simulations favor solid body rotation since, unlike the bipolar outflow kinematic models, they are able to produce both the large, >40 m s(-1)arcsec(-1)