Kevin Croxall (OSU)
The metal content of a galaxy is one of the most important properties used
to distinguish between viable evolutionary scenarios and strongly influences
many of the physical processes in the ISM. An absolute and robust
calibration of extragalactic metallicities is essential in constraining
models of chemical enrichment, chemical evolution, and the cycle of baryons
in the cosmos. Despite this strong dependence on abundance, the calibration
of nebular abundances from nebular emission lines remains uncertain.
Different calibrations of the abundance scale require different assumptions,
which may or may not be valid, and measurements, not all of which are easily
obtained. Using the MODS spectrographs on the Large Binocular Telescope we
have an opportunity to resolve these longstanding uncertainties. I will
discuss our effort to determine the CHemical Abundances of Spirals (CHAOS)
by observing an large uniform sample of extragalactic HII regions where the
detection of numerous temperature sensitive lines permits direct
measurements of the gas-phase oxygen abundance.