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H. Lee, D. C. Jackson, E. D. Skillman (University of Minnesota), J. M. Cannon (Max-Planck-Institut für Astronomie), R. D. Gehrz, E. Polomski, C. E. Woodward (University of Minnesota)
Dwarf irregular galaxies display a correlation between metallicity (as gauged by interstellar medium chemical abundances) and total galaxy luminosity (at optical wavelengths). It is possible that this relationship arises from mass loss due to galactic winds. However, the relationship at optical wavelengths shows a large dispersion, and part of the dispersion may be due to variations in luminosity caused by differences in the star formation rate. Infrared luminosities are less affected by changes in the star formation rate, so it is of interest to study the luminosity-metallicity relationship at infrared wavelengths. We present results for IRAC 4.5 \mum luminosities for nearby dwarf irregular galaxies observed under the Spitzer GTO program #128 (P. I. R. Gehrz). At this wavelength, the infrared luminosity of metal-poor dwarf galaxies is still dominated by the light of the underlying stellar population, and is not contaminated by PAH emission. With the inclusion of public release data for additional dwarf galaxies from the SINGS Legacy program, we have constructed an infrared luminosity-metallicity relationship for dwarf irregular galaxies. Further implications regarding gas fraction measures and the chemical evolution of dwarf galaxies are discussed. H.~L. and E.~D.~S. acknowledge partial support from a NASA LTSARP grant NAG~5--9221 and the University of Minnesota. Additional support for this work was provided by NASA through contract #1256406 issued to R.~D.~G. by JPL/Caltech.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.