MORPHOLOGY OF STAR-FORMATION REGIONS IN IRREGULAR GALAXIES

The location of H rr regions, which indicates the locus of present sta r formation in galaxies, is analysed for a large collection of 110 irr egular galaxies (Irr) imaged in Ha! and nearby continuum. The analysis is primarily by visual inspection, although a two-dimensional quantit ative measure is also employed. The two different analyses yield essen tially identical results. Hn regions appear preferentially at the edge s of the light distribution, predominantly on one side of the galaxy, contrary to what is expected from stochastic self-propagating star for mation scenarios. This peculiar distribution of star-forming regions c annot be explained by a scenario of star formation triggered by an int eraction with extragalactic gas, or by a strong one-armed spiral patte rn.