Elemental Abundance Variations and Chemical Enrichment from Massive Stars in Starbursts. Ⅱ. NGC 1569

摘要

We present a long-slit optical spectrophotometric survey covering 0.05 kpc~2 in the nearby irregular "post-starburst" galaxy NGC 1569 to search for chemical gradients and inhomogeneities in the inter- stellar medium. Despite the presence of two massive evolved star clusters and numerous H Ⅱ regions, we find no evidence for chemical gradients or inhomogeneities that may be attributed to enrichment from the recent star formation activity. The chemical properties at all locations are consistent with the results from the highest signal-to-noise ratio spectra: 12 + log (O/H) = 8.19 + - 0.02, log (N/O) = -1.39 + - 0.05, He/H = 0.080 + -0.003. No localized chemical self-enrichment ("pollution") from massive star evolution is found, even though the data are sensitive to the chemical yields from as few as two or three massive stars.