The Neutral Gas Dynamics of the Nearby Magellanic Irregular Galaxy UGCA
  105
  We present new low-resolution HI spectral line imaging, obtained with the
Karl G. Jansky Very Large Array (JVLA), 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)x10^8 Solar masses] system harbors a large neutral gas disk
(HI radius ~7.2 kpc at the N_HI=10^20 cm^-2 level) that is roughly twice as
large as the stellar disk at the B-band R_25 isophote. 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)x10^9 Solar masses, is ~10 times as large as the luminous baryonic
components (neutral atomic gas and stars). The proximity and favorable
inclination (55 degrees) 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.
