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The census of Galactic H ii regions is vastly incomplete in the southern sky. We use the Australia Telescope Compact Array to observe 4-10 radio continuum and hydrogen radio recombination line (RRL) emission from candidate H ii regions in the Galactic zone 250° < ℓ < 344°,|b|<4°. In this first data release, we target the brightest H ii region candidates and observe 282 fields in the direction of at least one previously known or candidate H ii 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 H ii regions. After averaging ∼18 RRL transitions, we detect 77 RRL velocity components toward 76 previously known H ii regions and 267 RRL velocity components toward 256 H ii region candidates. The discovery of RRL emission from these nebulae increases the number of known Galactic H ii 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 Southern H Region Discovery Survey has now discovered 295 Galactic H ii regions. In the next data release, we expect to add ∼200 fainter and more distant nebulae.
Bibliographical noteCopyright 2019 The American Astronomical Society. First published in the Astrophysical Journal Supplement Series, 240(2), 24, 2019, published by IOP Publishing. The original publication is available at http://www.doi.org/10.3847/1538-4365/aaf8ba. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.
- Galaxy: kinematics and dynamics
- Galaxy: structure
- H II regions
- ISM: kinematics and dynamics
- radio lines: ISM
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