AAS 205th Meeting, 9-13 January 2005
Session 93 Dwarf Galaxies
Poster, Wednesday, January 12, 2005, 9:20am-6:30pm, Exhibit Hall

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[93.17] Examining the Offset Between Nebular and Stellar Oxygen Abundances in the Local Group Dwarf Irregular Galaxy WLM

E. D. Skillman, H. Lee (Univ. of Minnesota), K. A. Venn (Macalester College)

New optical spectra of 13 H~II regions in WLM were obtained with the EFOSC2 instrument on the 3.6-m telescope at La Silla. From measurements of the temperature-sensitive [O~III]\lambda 4363~Å\ emission line, we derive a mean oxygen abundance of 12+log(O/H) = 7.83 ±0.06, which corresponds to [O/H] = -0.83~dex, or 15% of the solar value. Our reported nebular oxygen abundance agrees with values published in the literature, and is marginally consistent with the mean stellar magnesium abundance [Mg/H] = -0.62. However, there is still a 0.62~dex discrepancy between the oxygen abundance derived for the A-type supergiant star WLM~15 ([O/H] = -0.21) and the nebular value. There may be a connection between the position of WLM~15, the location of a second H~I peak, and regions of higher internal extinction on the southeast side of the galaxy. E.~D.~S. and H.~L. acknowledge partial support from a NASA LTSARP grant NAG~5--9221 and from the University of Minnesota. K.~A.~V. thanks the National Science Foundation for support through a CAREER award AST~99--84073.

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