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C.A. Tremonti (Johns Hopkins), D. Calzetti (STScI), T.M. Heckman (Johns Hopkins), C. Leitherer (STScI)
Previous high resolution ultraviolet spectra of starburst galaxies have focused principally on the UV-bright star forming clusters. However, in many nearby starburst galaxies, the young clusters contribute a relatively modest portion of the UV light (~10 - 50%). Since the rest frame UV spectra of high redshift star-forming galaxies are perforce spatially integrated, it is important to understand the contribution that both the field and clusters make. To this end, we have obtained a STIS longslit ultraviolet spectrum of the nearby starburst galaxy NGC 5253. The spectrum samples a physical area of ~450 pc and includes 4 bright clusters (3 of which have been studied at other wavelengths), 4 fainter clusters, and a region apparently devoid of clusters which we take to be the field. The spectra have approximately 2 Åresolution and include the stellar wind lines of NV, SiIV, and CIV, as well as a host of interstellar features. A comparison of the field and cluster spectra shows that the line strengths and shapes of both the stellar and interstellar features differ significantly. We use stellar evolutionary synthesis models to obtain ages for the clusters, and to investigate the plausibility of a non-Salpeter IMF in the field population. We suggest that the substantial differences of the UV cluster and field spectra result from the field having a different IMF or a different star-formation history than the clusters.
The author(s) of this abstract have provided an email address for comments about the abstract: cat@pha.jhu.edu