CHemical Abundances Of Spirals: Direct Abundances of NGC 2403

Accurate chemical abundance gradients of nearby galaxies are useful in determining the stellar evolution of these galaxies and are necessary for calibrating abundance techniques at high redshift. The "direct" method of determining chemical abundances is limited by the ability to detect faint, temperature-sensitive auroral lines. Using the Multi-Object Double Spectrograph (MODS) on the Large Binocular Telescope (LBT) to cover the optical spectrum at high sensitivity, the CHemical Abundance Of Spirals (CHAOS) project has, to date, detected temperature-sensitive auroral lines and calculated direct abundances in 190 H II regions in four nearby spiral galaxies. These high-quality measurements have led to new T_e-T_e relations, a possible explanation for the large intrinsic scatter within some direct abundance gradients, and the detection of a universal N/O gradient at R_g/R_e < 2.0. We present the new direct abundances measured by CHAOS and compare our results against existing direct, strong-line, and stellar abundance studies. NGC 2403 is especially interesting because its proximity allows for comparison between nebular abundances and stellar abundances from individual blue supergiants.