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 jbj < 1N3 to jbj < 2N3. 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 0 ; 1 0 ; 1:56 km s À1 ( FWHM ) and an rms noise of 2 K per 0:824 km s À1 channel. Continuum images made from channels without H i line emission have 1 0 (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, P6 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.

We have analyzed 793 atomic hydrogen emission and absorption spectrum pairs toward continuum background sources in the northern and southern Galactic plane. In this paper we focus on absorption features from cold gas in the outermost arms of the Galaxy. We find H i absorption associated on a global scale with the outer spiral arm (first and second Galactic quadrants). To a lesser extent we also see absorption associated with the most distant spiral arm in the third and fourth Galactic quadrants. In total, 236 spectra contain clear absorption features associated with the outermost spiral arms. Cool-phase gas therefore exists throughout these spiral arms. The mean distances between absorbing clouds are on the order of 90Y220 pc. We identify a number of striking H i structures with masses on the order of 10 5 Y10 6 M containing cool H i gas with temperatures below 100 K. These clouds are only marginally stable against gravitational collapse.

The VLA Galactic Plane Survey (VGPS) of the first Galactic quadrant was searched for H I emission with velocities well above the maximum velocity allowed by Galactic rotation. A sample of 17 small fast-moving clouds was identified. The distribution of the ensemble of clouds in longitude and velocity indicates that the clouds are part of the Galactic disk, despite their large forbidden velocity. The median angular diameter of the clouds detected in the VGPS is 3. ′ 4. These clouds would not be noticed in previous low resolution surveys because of strong beam dilution. Assuming each cloud is located at the tangent point, a median cloud has a diameter of 10 pc, H I mass of 60 M ⊙ , and a velocity more than 25 km s −1 beyond the local terminal velocity derived from 12 CO observations. Three clouds

A survey of H i line emission in the Galactic plane from Galactic longitude ℓ = 72.2 • to 149.0 • , and latitude b = −5.4 • to 7.2 • , has been made using the 26-m Telescope at DRAO. Spectra were observed at 0.2 • intervals of longitude and latitude, providing a survey which is fully sampled in the spatial domain. A detailed study of the antenna characteristics of the telescope allowed the correction of the spectra for stray radiation. The spectral resolution is 1.32 km s −1 and the LSR velocity range is −260 to 161 km s −1. The final spectra have an estimated T b scaling accuracy of 1%, and an estimated RMS noise in one channel (0.8245 km s −1) of 0.25 K. A region of suspected strong H i self-absorption at ℓ ∼ 92 • , b ∼ 3 • , has been identified. Comparison with spectra from the Leiden/Dwingeloo Survey is used to estimate the overall accuracy of the stray-radiation corrections. This comparison also shows that a small percentage (∼ 1%) of the spectra in the latter survey suffer from calibration errors exceeding 10%. A table of positions of the more discordant spectra is given.