VII Zw 403: HI Structure in a Blue Compact Dwarf Galaxy
  We present optical (UBVJ), ultraviolet (FUV, NUV), and high resolution atomic
hydrogen (HI) observations of the nearby blue compact dwarf (BCD), VII Zw 403.
We find that VII Zw 403 has a relatively high HI mass-to-light ratio for a BCD.
The rotation velocity is nominally 10-15 km/s, but rises to ~20 km/s after
correction for the ~8-10 km/s random motions present in the gas. The velocity
field is complex; including a variation in the position angle of the major axis
going from the NE to the SW parts of the galaxy. Our high resolution HI maps
reveal structure in the central gas, including a large, low-density HI
depression or hole between the southern and northern halves of the galaxy,
coincident with an unresolved x-ray source. Although interactions have been
proposed as the triggering mechanism for the vigorous star formation occurring
in BCDs, VII Zw 403 does not seem to have been tidally triggered by an external
interaction, as we have found no nearby possible perturbers. It also doesn't
appear to fall in the set of galaxies that exhibit a strong central mass
density concentration, as its optical scale length is large in comparison to
similar systems. However, there are some features that are compatible with an
accretion event: optical/HI axis misalignment, a change in position angle of
the kinematic axis, and a complex velocity field.
