2019MNRAS.488.3222S

Our GMRT (Giant Metrewave Radio Telescope) H I observations of the ultra-diffuse galaxy (UDG) UGC 2162, projected ∼ 300 kpc from the centre of the M 77 group, reveal it to a have an extended H I disc (R_ H I_/R25_ ∼ 3.3) with a moderate rotational velocity (V_rot ∼ 31 km s^–1). This V_rotis in line with that of dwarf galaxies with similar H I mass. We estimate an M_dyn of ∼1.14 x 10⁹ M_☉ within the galaxy's R_H I_ ∼ 5.2 kpc. Additionally, our estimates of M₂₀₀ for the galaxy from NFW models are in the range of 5.0-8.8 x 10¹⁰ M_☉. Comparing UGC 2162 to samples of UDGs with H I detections show it to have amongst the smallest R_e with its M_H I_/M*_ being distinctly higher and g - icolour slightly bluer than typical values in those samples. We also compared H I and dark matter (DM) halo properties of UGC 2162 with dwarf galaxies in the LITTLE THINGS sample and find its DM halo mass and profile are within the range expected for a dwarf galaxy. While we were unable to determine the origin of the galaxy's present-day optical form from our study, its normal H I rotation velocity in relation to its H I mass, H I morphology, environment, and dwarf mass DM halo ruled out some of the proposed ultra-diffuse galaxy formation scenarios for this galaxy.