THE H-II REGIONS AND THE VELOCITY-FIELD OF NGC-7331

The galaxy NGC 7331 has been observed with an IPCS through an Halpha f ilter for direct imagery and through a scanning Fabry-Perot interferom eter at Halpha wavelength with the 2.60 m Byurakan telescope to study the main physical parameters of 47 H II regions, diameter and luminosi ty, as well as their velocities. The cumulative diameter distribution of H II regions is well represented by an exponential function with th e parameters N0 = 272 and D0 = 95 pc. The Halpha luminosity function i s described by a power law with index -1.6. The Halpha velocity field of the galaxy is in good agreement with radio observations. Much less extended but offering a higher spatial resolution, it reveals non-circ ular motions, like the classical wiggles of the isovelocity lines when crossing a spiral arm, or the Z shape distortions of the isovelocity lines in the center possibly revealing an unseen bar.