Sizes and ages of star forming regions in galaxies

Abstract

Results of a multicolor surface photometry of 71 star forming regions in the nine late type spiral and irregular galaxies are presented. The sizes and the colors of the star forming regions are studied. The ages of the star forming regions are estimated using evolutionary synthesis method. Two groups of galaxies are distinguished. Within the first group of galaxies, the star forming regions belonging to a given galaxy have approximately the same age. In the second group, both young (from 1Myrs ) and intermediate age (several Gyrs ) star forming regions are observed. A correlation between the age and the size of star forming regions exists. A distribution of the star forming regions by size shows a maximum at 100-400 pc. It corresponds to stellar aggregations sizes (by Efremov) in hierarchical scale of star formation. A correlation between maximal diameters of the star forming regions and an absolute blue magnitude of a parental galaxy exists.