HST UV Imaging of the Starburst Regions in the Wolf-Rayet Galaxy He 2-10: Newly Formed Globular Clusters?

Abstract

We have obtained an ultraviolet image of the Wolf-Rayet galaxy He 2-10 using the Faint Object Camera aboard the Hubble Space Telescope and a filter centered at 2200 A. From previous analysis of optical spectra of He 2-10, it is known that O-type and Wolf-Rayet stars are present in large numbers in the nuclear starburst region. In the ultraviolet regime we observe the continuum radiation from the hot star population directly. We find that the star formation activity divides into smaller subunits ("knots"), a few of which may be resolved with diameters of ~10 pc. The extinction-corrected continuum luminosity at 2200 A of these knots spans a decade in energy, with a mean of ~10^38^ ergs s^-1^ A^-1^. The luminosities are compared to those predicted from starburst models for ages between 1 and 10 Myr, from which we estimate the masses of the knots to be between 10^5^ and 10^6^ M_sun_. We suggest that the knots are extremely young globular clusters which have been formed recently, perhaps as the result of an interaction or merger event. It is possible that many such young clusters of OB stars are located within other violent star-forming regions.