5 Conclusions

The main results of the present paper, where we analyze the kinematics of the ionized gas in NGC 3359 are summarized below.

• A velocity map of the ionized gas in the barred spiral NGC 3359 has been produced using Fabry-Perot observations. Analysis of this map shows a disc with an axisymmetric rotation pattern but also evidence of deviations from circular motions in the arms (streaming motions) and near the bar;

• We have calculated from the velocity map the disc kinematic parameters of NGC 3359, which are coincident with those found in the literature for this galaxy: $i=53\hbox{$^\circ$ }$, $V_{{\rm sys}}$ = 1006.8 km s^-1;

• The rotation curve of the galaxy shows a standard shape with an asymptotic rotation velocity of about 145 km s^-1. Both the rotation curve and the asymptotic rotation velocity are compatible with the previous H I determinations, although our results have a better spatial resolution;

• We present a map of the velocity residuals, subtracting the axysimetric rotation model from the observed velocity map, which shows prominent peaks in some areas of the disc, indicating non-circular motions of the following three kinds:

  1.

  Streaming motions in the spiral arms;

  2.

  Gas flows around the bar;

  3.

  Vertical motions associated with the turbulent dispersion in the brightest H II regions.

• The velocity dispersion map has been obtained and its radial distribution has been analyzed. We find a constant mean value with the radius of around 15 km s^-1; the peaks in velocity dispersion coincide with the luminosity peaks, i.e. correspond to the brightest H II regions;

• We have accurately analyzed the non circular motions around the bar and a simple model has been developed, which is able to explain the velocity gradients in this region as gas flowing in elliptical orbits around the bar. This, together with the presence in the bar region of strong star formation fits the general scenario of a bar in the process of formation.

Acknowledgements

The William Herschel Telescope is operated on the island of La Palma by the Royal Greenwich Observatory in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. We thank F. Garzón for his help with the English version of this paper. This work was partially supported by the Spanish DGICYT (Dirección General de Investigación Científica y Técnica) via Grants PB91-0525, PB94-1107 and PB97-0219. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.