Polycyclic aromatic hydrocarbon ( PAH ) emission has long been proposed to be a potential star formation rate indicator , as it arises from the photodissociation region bordering the Strömgren sphere of young , massive stars .
We apply a recently developed technique of mid-infrared spectral decomposition to obtain a uniform set of PAH measurements from Spitzer low-resolution spectra of a large sample of star-forming galaxies spanning a wide range in stellar mass ( M _ { \star } \approx 10 ^ { 6 } -10 ^ { 11.4 } M _ { \odot } ) and star formation rate ( \sim 0.1 - 2000 M _ { \odot } yr ^ { -1 } ) .
High-resolution spectra are also analyzed to measure [ Ne II ] 12.8 \mu m and [ Ne III ] 15.6 \mu m , which effectively trace the Lyman continuum .
We present a new relation between PAH luminosity and star formation rate based on the [ Ne II ] and [ Ne III ] lines .
Calibrations are given for the integrated 5–15 \mu m PAH emission , the individual features at 6.2 , 7.7 , 8.6 , and 11.3 \mu m , as well as several mid-infrared bandpasses sensitive to PAH .
We confirm that PAH emission is suppressed in low-mass , dwarf galaxies , and we discuss the possible physical origin of this effect .