Metallicity–luminosity relation for 125,958 SDSS DR4 star-forming galaxies (e.g., Tremonti et al. 2004; Prieto et al. 2008). They are binned into 0.1 mag and 0.025 dex bins and the smoothed contours (3 × 3 bins) are drawn for 1, 10, 50, 100, and 200 objects per bin, counting from the outer contour. The figure is analogous to Figure  1 from Stanek et al. (2006). SDWFS-MT-1 is shown as the filled pentagon (lower left). A handful of local GRBs with associated SNe (and two SNe) with known host metallicities and luminosities are shown with open circles (small pentagons). The arrows show M _B for five host galaxies of high-luminosity SNe with unknown oxygen abundances. They are, from left to right, SN 2005ap, SN 2006tf, SN 2008fz, SN 2008es, and SN 2006gy (see Section 3.3). The Large Magellanic Cloud/Small Magellanic Cloud oxygen abundances are adopted following Peeples et al. (2008) and the Milky Way's (solar) are from Delahaye et al. (2010), while the absolute magnitudes are from Karachentsev (2005).