2012AJ....144...82C

We present new low-resolution H I spectral line imaging, obtained with the Karl G. Jansky Very Large Array, of the star-forming Magellanic irregular galaxy UGCA 105. This nearby (D = 3.39±0.25 Mpc), low-mass (M_HI = 4.3±0.5 x10⁸ M_☉) system harbors a large neutral gas disk (H I radius ∼7.2 kpc at the N_HI = 10²⁰/cm2 level) that is roughly twice as large as the stellar disk at the B-band R₂₅isophote. We explore the neutral gas dynamics of this system, fitting tilted ring models in order to extract a well-sampled rotation curve. The rotation velocity rises in the inner disk, flattens at 72±3 km/s, and remains flat to the last measured point of the disk (∼7.5 kpc). The dynamical mass of UGCA 105 at this outermost point, (9±2)x10⁹ M_☉, is ∼10 times as large as the luminous baryonic components (neutral atomic gas and stars). The proximity and favorable inclination (55°) of UGCA 105 make it a promising target for high-resolution studies of both star formation and rotational dynamics in a nearby low-mass galaxy.