The HI Chronicles of LITTLE THINGS BCDs II: The Origin of IC 10's HI Structure

In this paper we analyze Very Large Array (VLA) telescope and Green Bank Telescope (GBT) atomic hydrogen (HI) data for the LITTLE THINGS(1) blue compact dwarf galaxy IC 10. The VLA data allow us to study the detailed HI kinematics and morphology of IC 10 at high resolution while the GBT data allow us to search the surrounding area at high sensitivity for tenuous HI. IC 10's HI appears highly disturbed in both the VLA and GBT HI maps with a kinematically distinct northern HI extension, a kinematically distinct southern plume, and several spurs in the VLA data that do not follow the general kinematics of the main disk. We discuss three possible origins of its HI structure and kinematics in detail: a current interaction with a nearby companion, an advanced merger, and accretion of intergalactic medium. We find that IC 10 is most likely an advanced merger or a galaxy undergoing accretion. 1:Local Irregulars That Trace Luminosity Extremes, The HI Nearby Galaxy Survey; https://science.nrao.edu/science/surveys/littlethingsComment: 36 pages, 17 figures, accepted for publication in The Astronomical Journa

Limits on the HI content of the dwarf galaxy Hydra II

Sensitive 21cm HI observations have been made with the Green Bank Telescope toward the newly-discovered Local Group dwarf galaxy Hydra II, which may lie within the leading arm of the Magellanic Stream. No neutral hydrogen was detected. Our 5-sigma limit of MHI < 210 solar masses for a 15 km/s linewidth gives a gas-to-luminosity ratio MHI/L_V < 2.6 x 10^{-2} Mo / Lo. The limits on HI mass and MHI/L_V are typical of dwarf galaxies found within a few hundred kpc of the Milky Way. Whatever the origin of Hydra II, its neutral gas properties are not unusual.Comment: Accepted for publication in Astronomy & Astrophysic