The Neutral Gas Dynamics of the Nearby Magellanic Irregular Galaxy UGCA 105
American Astronomical Society, AAS Meeting #221, #242.03
Published in Jan 2013
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 (MHI= 4.3 ± 0.5x108 Solar masses) system harbors a large neutral gas disk (HI radius ~7.2 kpc at the NHI = 1020 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-1, 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 Solar masses, 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.
(c) 2013: American Astronomical Society