Resolved HI in two ultra-diffuse galaxies from contrasting non-cluster
  environments
  We report on the first resolved HI observations of two blue ultra-diffuse
galaxies (UDGs)using the Giant Metrewave Radio Telescope (GMRT). These
observations add to the sofar limited number of UDGs with resolved HI data. The
targets are from contrasting non-cluster environments: UDG-B1 is projected in
the outskirts of Hickson Compact Group 25 and Secco-dI-2 (SdI-2) is an isolated
UDG. These UDGs also have contrasting effective radii with Re of 3.7 kpc
(similar to the Milky Way) and 1.3 kpc respectively. SdI-2 has an unusually
large MHI/M* ratio =28.9, confirming a previous single dish HI observation.
Both galaxies display HI morphological and kinematic signatures consistent with
a recent tidal interaction, which is also supported by observations from other
wavelengths, including optical spectroscopy. Within the limits of the
observations' resolution, our analysis indicates that SdI-2 is dark
matter-dominated within its HI radius and this is also likely to be the case
for UDG-B1. Our study highlights the importance of high spatial and spectral
resolution HI observations for the study of the dark matter properties of UDGs.
