GASS: The Parkes Galactic All-Sky Survey. II. Stray-Radiation Correction
  and Second Data Release
  The Parkes Galactic All-Sky Survey (GASS) is a survey of Galactic atomic
hydrogen (HI) emission in the southern sky observed with the Parkes 64-m Radio
Telescope. The first data release was published by McClure-Griffiths et al.
(2009). We remove instrumental effects that affect the GASS and present the
second data release. We calculate the stray-radiation by convolving the all-sky
response of the Parkes antenna with the brightness temperature distribution
from the Leiden/Argentine/Bonn (LAB) all sky 21-cm line survey, with major
contributions from the 30-m dish of the Instituto Argentino de Radioastronomia
(IAR) in the southern sky. Remaining instrumental baselines are corrected using
the LAB data for a first guess of emission-free baseline regions. Radio
frequency interference is removed by median filtering. After applying these
corrections to the GASS we find an excellent agreement with the
Leiden/Argentine/Bonn (LAB) survey. The GASS is the highest spatial resolution,
most sensitive, and is currently the most accurate HI survey of the Galactic HI
emission in the southern sky. We provide a web interface for generation and
download of FITS cubes.
