Hot, Massive Stars in I Zw 18
NASA’s Goddard Space Flight Center, Mail Code 667, Greenbelt MD, USA
University of Arizona, Tucson AZ, USA
University of Maryland, College Park MD, USA
NASA’s Goddard Space Flight Center, Mail Code 667, Greenbelt MD, USA, and Adnet Systems, Inc., Rockville MD, USA
NASA’s Goddard Space Flight Center, Mail Code 667, Greenbelt MD, USA, and Sigma Space, Inc., Lanham MD, USA
NASA’s Goddard Space Flight Center, Mail Code 667, Greenbelt MD, USA, and Wyle Information Systems, McLean VA, USA
Abstract
We present the far-ultraviolet spectrum of the northwest component of I Zw 18, a blue compact galaxy having a very low metallicity. The spectrum is compatible with continuous star-formation over the past ~ 15 Myr (CSF age), and a very low metallicity, log Z/Zo ~ -1.7, although the stellar surface may be enhanced in carbon. Stellar winds are very weak, and the edge velocity of wind lines is very low (~ 250 km/s).
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