A Westerbork Synthesis Radio Telescope 327 MHz survey of the Galactic plane

The Westerbork Synthesis Radio Telescope (WSRT) has been used to survey the Galactic plane region 42 degrees < I < 92 degrees at a frequency of 327 MHz. We present images of the emission within \b\ < 1.6 degrees at resolution of 1' x 1' csc delta and detection level as low as 10 mJy beam(-1). Inspection of the survey image has produced a catalog of nearly 4000 discrete sources with sizes less than about similar to 3'. The catalog of these sources and FITS files of seven images covering the survey area are available on the World Wide Web at http : //www.ras.ucalgary.ca/wsrt_survey.html. Approximately 15% of the sources are resolved, with dimensions of 1'-3'. The spatial distribution of resolved sources shows concentrations toward the spiral arms and follows the warping of the Galactic disk over the length of the survey region, indicating that a sizable fraction is Galactic. Spectral indices are calculated for 1313 sources detected in other radio surveys at frequencies greater than 408 MHz. The resolved sources exhibit a bimodal spectral index distribution, with distinct nonthermal and thermal populations. Comparison with the IRAS Point Source Catalogue results in 118 identifications between WSRT and IRAS sources. Most of these are thermal radio sources associated with compact Galactic objects such as H II regions and planetary nebulae. A search for variability among 2148 of the compact sources has resulted in 29 candidate low-frequency variable sources.