A search for non-circular flows in the extended HI disc of NGC 2915
  NGC 2915 is a nearby blue compact dwarf with a differentially rotating HI
disc extending out to ~ 5 R-band R_{25} radii. This disc serves as an ideal
tracer of the system's gravitational potential in regions of the galaxy that
are dominated by dark matter. We use new HI synthesis observations of NGC 2915,
obtained with the Australia Telescope Compact Array, to search for non-circular
flows within the outer HI disc. Two independent methods are used, and the
results of each interpreted in the context of relevant axisymmetric and
non-axisymmetric perturbations of the potential. We find evidence for: (1)
elliptical streaming associated with the spiral structure of the HI disc and
the central bar-like feature in the mass distribution, (2) a spherical dark
matter halo, and (3) an axisymmetric radial outflow of ~ 5-17 km/s (~ 6-20
percent of the circular speed). A possible bar-like perturbation of the
potential hinders attempts to unambiguously detect kinematic signatures of
radial flows in the HI velocity field. The radial outflows are inconsistent
with the plausible disc formation scenario in which gas from the surrounding
inter-galactic medium is deposited on the outer HI disc and then transported
towards the centre of the galaxy. They are, however, consistent with the
possibility of some material being re-distributed towards the outer disc in
order to conserve angular momentum as material flows inwards along a bar.
