THE DISTRIBUTION AND NATURE OF STAR-FORMATION REGIONS IN NGC-1792

A strong asymmetry with respect to the major axis has been found in th e spatial distribution of H II regions in NGC 1792 detected on our H a lpha image. In the radio continuum, this asymmetry is even stronger th an in H alpha, indicating that supernova activity set in earlier in th e northeastern half of the disk than southwest of the nucleus. This su ggests that we are viewing spatially propagating star formation (SF) i n the disk, which set in about 10(7) yr ago. The most luminous H II re gions are distinctly different from the rest of the star-forming regio ns in NGC 1792, showing up as a peak in the H alpha luminosity near L( H alpha) similar or equal to 3 x 10(39) ergs s(-1) Around these giant H II regions large amounts of diffuse ionized gas are found, suggestin g that this gas is heated by UV radiation escaping these regions. Attr ibuting the radiation coming from the luminous H II regions to a tempo rarily increased level of SF activity, we estimate that on the order o f 1200 OB stars were formed in each of them, with integrated Lyman-con tinuum luminosities in the range of 6 x 10(51) s(-1). Although increas ed significantly near the galactic turnover of rotation, the global SF rate in NGC 1792 is only marginally affected (similar to 20%) by this phenomenon. The most plausible explanation of these results and those obtained for NGC 1808, the interaction partner of NGC 1792, is that t he currently on-going SF was triggered by an interaction some 10(8) yr ago.