A 5deg x 5deg deep HI survey of the M81 group: II. HI distribution and
  kinematics of IC 2574 and HIJASS J1021+68
  We analyse the eastern region of a $5^\circ\times5^\circ$ deep HI survey of
the M81 group containing the dwarf galaxy IC 2574 and the HI complex HIJASS
J1021+68, located between the dwarf and the M81 system. The data show that IC
2574 has an extended HI envelope that connects to HIJASS J1021+68 in the form
of a collection of small clouds, but no evident connection has been found
between IC 2574 and the central members of the M81 group. We argue, based on
the morphology of the clouds forming HIJASS J1021+68 and its velocity
distribution, that the complex is not a dark galaxy as previously suggested,
but is instead a complex of clouds either stripped from, or falling onto the
primordial HI envelope of IC 2574. We also use the deep HI observations to map
the extended HI envelope around IC 2574 and, using a 3D tilted-ring model, we
derive the rotation curve of the galaxy to a larger extent than has been done
before. Combining the obtained rotation curve to higher resolution curves from
the literature, we constrain the galaxy's dark matter halo parameters.
