Presentation #105.08 in the session Molecular Clouds and the ISM — iPoster Session.
We introduce the Far-Infrared Abundances (FIRA) project, which combines far- and mid-infrared fine-structure line-emission, multi-band radio-continuum, and optical integral-field unit (IFU) observations to determine direct absolute gas-phase oxygen-abundances in a sample of extragalactic HII regions. The benefit of this FIR-based abundance-method is its insensitivity to both the temperature of the line-emitting gas and intervening dust attenuation. In our introductory paper, we target the nearby spiral-galaxy M101, comparing the derived abundances to those calculated as part of the CHemical Abundances Of Spirals (CHAOS) project, an optical direct-abundance program. We find excellent agreement between the FIR and optical direct-abundance methods, validating the FIRA methodology and laying the groundwork for the application of this technique to the dusty star-forming environments of local ultra-luminous infrared galaxies (ULIRGs) and early-Universe galaxies alike.