Skillman, Andrew R. Marble, Liese van Zee, Charles W. Engelbracht, Janice C. Lee, Robert C. Kennicutt, Jr., Daniela Calzetti, Daniel A. Dale, and Benjamin D. Johnson'
title: Direct Oxygen Abundances for Low Luminosity LVL Galaxies
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INTRODUCTION {#sec:intro}
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There is a fundamental relationship between the mass of stars in a galaxy and its metallicity evolution [e.g., @tremonti04 hereafter, the M-Z relation]. Empirically, this has been observed as a luminosity-metallicity relationship (hereafter, the L-Z relation) for low redshift dwarf galaxies [e.g., @lequeux79; @skillman89; @lee06a and references therein] and spiral galaxies [e.g., @mccall85; @garnett87; @zaritsky94; @tremonti04 and references therein]. This relationship is observed over a range of 10 magnitudes in galaxy optical luminosity [e.g., @zaritsky94; @tremonti04; @lee06a], but the data are relatively sparse at the low luminosity end where the intrinsic faintness of these galaxies makes metallicity determinations more difficult.

The physical driver of the M-Z relation remains under debate. One possibility is that low-mass galaxies are younger, in that they only recently started forming stars [@noeske2000; @leitner2011]. Another is that they have been less efficient at producing metals [@brooks07]. Many studies favor a different interpretation, where supernova driven winds preferentially expel metals from low-mass galaxies, resulting in a lower effective 