The Calibration of Polycyclic Aromatic Hydrocarbon Dust Emission as a Star Formation Rate Indicator in the AKARI NEP Survey

Polycyclic aromatic hydrocarbon (PAH) dust emission has been proposed as an effective extinction-independent star formation rate (SFR) indicator in the mid-infrared, but this may depend on conditions in the interstellar medium. The coverage of the AKARI/Infrared Camera (IRC) allows us to study the effects of metallicity, starburst intensity, and active galactic nuclei on PAH emission in galaxies with f(nu )(L18W) less than or similar to 19 AB mag. Observations include follow-up, rest-frame optical spectra of 443 galaxies within the AKARI North Ecliptic Pole survey that have IRC detections from 7 to 24 mu m. We use optical emission line diagnostics to infer SFR based on H alpha and [O ii]lambda lambda 3726, 3729 emission line luminosities. The PAH 6.2 mu m and PAH 7.7 mu m luminosities (L(PAH 6.2 mu m) and L(PAH 7.7 mu m), respectively) derived using multiwavelength model fits are consistent with those derived from slitless spectroscopy within 0.2 dex. L(PAH 6.2 mu m) and L(PAH 7.7 mu m) correlate linearly with the 24 mu m dust-corrected H alpha luminosity only for normal, star-forming "main-sequence" galaxies. Assuming multilinear correlations, we quantify the additional dependencies on metallicity and starburst intensity, which we use to correct our PAH SFR calibrations at 0 < z < 1.2 for the first time. We derive the cosmic star formation rate density (SFRD) per comoving volume from 0.15 less than or similar to z less than or similar to 1. The PAH SFRD is consistent with that of the far-infrared and reaches an order of magnitude higher than that of uncorrected UV observations at z similar to 1. Starburst galaxies contribute greater than or similar to 0.7 of the total SFRD at z similar to 1 compared to main-sequence galaxies.