The VLA Galactic Plane Survey

Abstract

The VLA Galactic Plane Survey (VGPS) is a survey of H I and 21 cm continuum emission in the Galactic plane between longitude 18° and 67° with latitude coverage from |b| < 13 to |b| < 23. The survey area was observed with the Very Large Array in 990 pointings. Short-spacing information for the H I line emission was obtained by additional observations with the Green Bank Telescope. H I spectral line images are presented with a resolution of 1' × 1' × 1.56 km s-1 (FWHM) and an rms noise of 2 K per 0.824 km s-1 channel. Continuum images made from channels without H I line emission have 1' (FWHM) resolution. The VGPS images reveal structures of atomic hydrogen and 21 cm continuum as large as several degrees with unprecedented resolution in this part of the Galaxy. With the completion of the VGPS, it is now possible for the first time to assess the consistency between arcminute-resolution surveys of Galactic H I emission. VGPS images are compared with images from the Canadian Galactic Plane Survey (CGPS) and the Southern Galactic Plane Survey (SGPS). In general, the agreement between these surveys is impressive, considering the differences in instrumentation and image-processing techniques used for each survey. The differences between VGPS and CGPS images are small, ≲6 K (rms) in channels in which the mean H I brightness temperature in the field exceeds 80 K. A similar degree of consistency is found between the VGPS and SGPS. The agreement we find between arcminute-resolution surveys of the Galactic plane is a crucial step toward combining these surveys into a single uniform data set that covers 90% of the Galactic disk: the International Galactic Plane Survey. The VGPS data will be made available on the World Wide Web through the Canadian Astronomy Data Centre.