Hubble Space Telescope observations of He 2-10: Outflows and young super-star clusters

We use Hubble Space Telescope (HST) WFPC2 optical images and GHRS ultraviol et spectroscopy to examine the recent star formation history and properties of the Wolf-Rayet galaxy He 2-10. The high spatial resolution afforded by HST has allowed the identification of a number of starburst knots, or "supe r-star clusters" (SSCs). The spatial morphology newly revealed by these HST images exhibits a prominent dust lane between the starburst regions known as A and B and a spur of material to the northwest of the nuclear region. B roadband photometry of the SSCs confirms that these objects have ages as yo ung as a few Myr and masses up to 10(5) M-circle dot. Narrowband Ha photome try of the SSCs indicates large equivalent widths for nearly half of them, consistent with ages less than 10 Myr. Since an appreciable fraction of SSC s are this young, the star formation history necessarily must be strongly p eaked and not continuous. GHRS UV spectra were obtained for sections of the two starburst regions and were used to determine the parameters of the starburst regions. For a stel lar population produced in a single burst with stellar masses between 1 and 100 M-circle dot, the UV luminosities indicate regions A and B have masses between 1.6-2.6 x 10(6) M-circle dot and 2.6-6.6 x 10(4) M-circle dot, res pectively. The total starburst mass was between 1 and 100 M-circle dot cons istent with the UV luminosity ranges between 1.6 and 2.6 x 10(6) M-circle d ot and 2.6 and 6.6 x 10(4) M-circle dot for regions A and B, respectively. The observed integrated H alpha flux is similar to that predicted by the mo dels, implying that the leakage and/or dust absorption of Lyman continuum p hotons from the starburst regions is small. The integrated Ha equivalent wi dths of the two regions are substantially smaller than predicted, We attrib ute this to contamination by the continuum in the starburst regions (the st arburst knots do not uniformly fill the GHRS apertures). The UV spectroscopy of starburst region A indicates a large-scale outflow o f the interstellar medium of He 2-10 with speeds of at least 360 km s(-1) a nd a total mass of at least 106 Mo. We estimate that the mass in metals whi ch He 2-10 will expel is enough to raise primordial abundances in approxima te to 1 Mpc(3) to 10(-3) to 10(-2) solar.