The Southern HII Region Discovery Survey I: The Bright Catalog
  The census of Galactic HII regions is vastly incomplete in the Southern sky.
We use the Australia Telescope Compact Array (ATCA) to observe 4-10 GHz radio
continuum and hydrogen radio recombination line (RRL) emission from candidate
HII regions in the Galactic zone 259 deg < l < 344 deg, |b| < 4 deg. In this
first data release, we target the brightest HII region candidates and observe
282 fields in the direction of at least one previously-known or candidate HII
region. We detect radio continuum emission and RRL emission in 275 (97.5%) and
258 (91.5%) of these fields, respectively. We catalog the ~7 GHz radio
continuum peak flux densities and positions of 80 previously-known and 298
candidate HII regions. After averaging ~18 RRL transitions, we detect 77 RRL
velocity components towards 76 previously-known HII regions and 267 RRL
velocity components towards 256 HII region candidates. The discovery of RRL
emission from these nebulae increases the number of known Galactic HII regions
in the surveyed zone by 82%, to 568 nebulae. In the fourth quadrant we discover
50 RRLs with positive velocities, placing those sources outside the Solar
circle. Including the pilot survey, the SHRDS has now discovered 295 Galactic
HII regions. In the next data release we expect to add ~200 fainter and more
distant nebulae.
