Isolating Clusters with Wolf-rayet Stars in I Zw 18
نویسنده
چکیده
We present UV images and spectra of the starburst galaxy I Zw 18, taken with the Space Telescope Imaging Spectrograph. The high spatial resolution of these data allows us to isolate clusters containing Wolf-Rayet stars of the subtype WC. Our far-UV spectra clearly show C IV λλ1548,1551 and He II λ1640 emission of WC stars in two clusters: one within the bright (NW) half of I Zw 18, and one on the outskirts of this region. The latter spectrum is unusual, because the C IV is seen only in emission, indicating a spectrum dominated by WC stars. These data also demonstrate that the H I column in I Zw 18 is strongly peaked in the fainter (SE) half of I Zw 18, with a column depth far larger than that reported in previous analyses. Subject headings: stars: Wolf-Rayet – galaxies: starburst – galaxies: stellar content – ultraviolet: galaxies
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