Properties of Bulgeless Disk Galaxies. I. Atomic Gas
  We study the neutral hydrogen properties of a sample of 20 bulgeless disk
galaxies (Sd - Sdm Hubble types), an interesting class that can be used to
constrain galaxy formation and evolution, especially the role of mergers versus
internal processes. Our sample is composed of nearby (within 32 Mpc),
moderately inclined galaxies that bracket the circular velocity of 120 km/s,
which has been found to be associated with a transition in dust scale heights
in edge-on, late-type disks. Here we present HI channel maps, line profiles,
and integrated intensity maps. We also derive kinematic parameters, including
the circular velocity, from rotation curve analyses and calculate the
integrated HI flux and HI mass for each galaxy in the sample. Three of the 20
galaxies in our sample have kinematically distinct outer components with major
axes that differ by 30 - 90 degrees from the main disk. These distinct outer
components may be due to a recent interaction, which would be somewhat
surprising because the disks do not contain bulges. We will use the data
products and derived properties in subsequent investigations into star
formation and secular evolution in bulgeless disks with circular velocities
above and below 120 km/s.
