The velocity field of the barred spiral galaxy NGC 1300 revisited

The re-reduction, described in Jorsater & van Moorsel (1995), of NGC 1300 VLA HI observations, originally obtained by M. England, motivates a new analysis of the velocity field and rotation curve. Fitting tilted ring models to the HI velocity data, we find the new values for the orientation parameters of NGC 1300 to be PA(lon) = 267 degrees +/- 2 degrees and i = 35 degrees +/- 5 degrees. Subsequently, the H I rotation curve is extracted, and a residual velocity map constructed. The H I velocity residuals in the bar region are found to be consistent with elliptical motion aligned with the bar major axis. Further out the residual velocities correlate with the position of the H I spiral arms. We use 16 optical long slit emission line spectra, covering mainly the nuclear, bar, and inner arm region, to resolve the inner part of the velocity field. Three new spectra are presented in this investigation, and the remaining 13 are found in the literature. The optical velocities reveal a sharply rising rotation curve in the inner R < 10 '', not seen in the HI data due to beam-smearing. The optical velocity field is weighted together with the HI velocities to produce a combined velocity field. This velocity field is interpreted using hydrodynamical models in a subsequent paper by Lindblad & Kristen (1996).