The supernebula and protoglobular cluster in NGC 5253

Abstract

. A compact and bright radio and infrared source within the starburst center of the dwarf galaxy NGC 5253 appears to be an extremely large compact HII region. The high density (n e ~ few xlO 4 cm -3 ) and size (~l-2 pc) of the nebula require the ionization equivalent of at least 4000 07 stars. We suggest that this optically obscured nebula is a forming super star cluster, or protoglobular cluster, with an age of a few hundred thousand years.