The Southern Galactic Plane Survey: H i Observations and Analysis

We describe the HI component of the Southern Galactic Plane Survey (SGPS).The SGPS is a large-scale project to image at arcminute resolution the HIspectral line and 21 cm continuum emission in parts of the plane of the MilkyWay. The survey covers Galactic longitudes 253 deg < l < 358 deg and latitudes|b| <1.5 deg (SGPS I), plus a first quadrant extension covering 5 deg < l < 20deg and |b| <1.5 deg (SGPS II). The survey combines data from the AustraliaTelescope Compact Array and the Parkes Radio Telescope for sensitivity toangular scales ranging from 2 arcminutes to several degrees. The combined datacover 325 sq-deg and have an rms sensitivity of 1.6 K. Here we describe the HIobservations and data reduction in detail, and present examples from the finaldata products. The complete dataset is publicly available through the AustraliaTelescope National Facility's HI Surveys archive. This dataset provides anunprecedented view of the neutral component of interstellar hydrogen in theinner Milky Way.