Radial distributions of oxygen abundances in the disks of our target galaxies. The plus signs are abundances derived through the T_e method, the circles are abundances obtained through the C_NS method, and the squares are those inferred through the C_ON method. The filled symbols show abundances based on our SALT spectra, the open (blue) symbols are abundances based on spectra from the literature (see text). The solid line in each panel is the best linear fit to the data points with galactocentric distances less than the isophotal R₂₅ radius. (A color version of this figure is available in the online version.)