Star formation in giant extragalactic H II regions

Abstract

Star formation properties in Giant Extragalactic H II Regions (GE-Hrs) are investigated using the optical photometry and evolutionary population synthesis models. We find it necessary to have differential extinction between embedded cluster stars and the surrounding nebulosity in GEHRs, with about 50% of the cluster protons escaping the nebula unattenuated. GEHRs are found to contain hot massive stars and evolved red supergiants simultaneously, implying more than one event of star formation in the last 10 Myr. We have identified some regions on our images which may be examples of young and old regions spatially separated by 40-100 pc. Extended duration of star formation in GEHRs may be as a result of a trigger from the earlier star formation event