1 Introduction

Figure 1: The 965 pointings of the VLA survey that were used in the data reduction; no data were obtained for 88 pointings out of 1053. In reality the maps were square ( $41\hbox {$^\prime $ }\times 41\hbox {$^\prime $ }$ in $\alpha ,\delta$) and overlapping. A single missing pointing (of which there are 50, cf. around $\ell =42$$^\circ$) leaves a hole of $\sim \,10\hbox {$^\prime $ }\times 10\hbox {$^\prime $ }$ in the coverage, but influences the sensitivity in a larger area

We have surveyed a large section of the galactic plane in the OH 1612-MHz satellite line. The aim of the survey was to sample the stellar dynamics in the plane, cutting through the major components of the Galaxy. Very strong radiation is emitted in the observed OH line by, amongst others, OH/IR stars (for a review see Habing 1996). These are particularly suitable tracers of the stellar dynamics for a variety of reasons. Most important is that they are easily observable in any region of the Galaxy, their line-of-sight velocity can be determined very accurately and they represent a large fraction of the stellar population. This article is the sequel to previous articles discussing the Australia Telescope Compact Array (ATCA) "Bulge'' ( $\vert\ell\vert < 10$$^\circ$, Sevenster et al. 1997a, Paper I) and "Disk'' ($\ell<-10$$^\circ$, Sevenster et al. 1997b, Paper II) parts of the survey. Here we discuss the results of the northern plane region, between $5^{\circ} \le \ell \le 45^{\circ}$ and $\vert b\vert \le 3^{\circ}$. This region was observed with the VLA in New Mexico.

Figure 2: a-c) The two larger panels on the left show the raw spectrum of a primary calibrator (1331+305), taken on 210594, averaged over all baselines (top) and after flagging with WSRFI (bottom). The smaller panels on the right show the single-integration, single-baseline spectra (i.e. visibilities) that were actually flagged by WSRFI. Most of these visibilities were flagged as "G" ( 3.1), except for the 7th plot, which was a "W"

We discuss the observations in Sect. 2 and the data reduction in Sect. 3. In Sect. 4 we give the results of this survey and in Sect. 5 a statistical analysis of the data, that, like Paper II, follows closely the analysis in Paper I. We summarize in Sect. 6.