Several authors have explored the field of gas dynamics in barred systems. One of the aims of these investigations was to compare the model gaseous response, due to some assumed underlying stellar gravitational field, with observed gas density distribution and kinematics of barred galaxies. The gas is known to respond in a highly non-linear way, and therefore should give clues to dynamical parameters like the mass distribution, positions and existence of principal resonances and thereby the pattern speed.High resolution HI data now exist for NGC 1365 (Jörsäter & van Moorsel 1995), and the kinematical HI data have been combined with optical long slit measurements to obtain the velocity field (Lindblad et al. 1995) used for extracting the rotation curve, representing the axisymmetric forces in NGC 1365, and for comparisons with models. A mosaic image of NGC 1365 in the J-band was used to compute the perturbing potential used in the models.

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A b s tra c t. -Optical emission line velocities in NGC 1365 are presented along 35 slit positions, of which 18 have not been published earlier. Diagrams of emission line velocities as function of distance along the slits are presented, and separate velocity fields are derived for the disc as given by the low excitation lines, combined with H i 21 cm VLA data, and for the nuclear outflow cone as given mainly by the high excitation lines. An algorithm for creating a velocity field and contour maps based on measurements along randomly oriented spectrograph slits is given in the Appendix. Detailed discussions and interpretations of these velocity fields are given elsewhere. The combined optical and 21 cm disc velocity field is available by an anonymous ftp.