Gass: The Parkes Galactic All-Sky Survey. I. Survey Description, Goals, and Initial Data Release

The Parkes Galactic All-Sky Survey (GASS) is a survey of Galactic atomic hydrogen (H I) emission in the Southern sky covering declinations δ ≤ 1° using the Parkes Radio Telescope. The survey covers 2π steradians with an effective angular resolution of ~16', at a velocity resolution of 1.0 km s-1, and with an rms brightness temperature noise of 57 mK. GASS is the most sensitive, highest angular resolution survey of Galactic H I emission ever made in the Southern sky. In this paper, we outline the survey goals, describe the observations and data analysis, and present the first-stage data release. The data product is a single cube at full resolution, not corrected for stray radiation. Spectra from the survey and other data products are publicly available online.