Calibrating the James Webb Space Telescope Filters as Star Formation Rate Indicators

We have calibrated the 6.5 m James Webb Space Telescope (JWST) mid-infrared (MIR) filters as star formation rate (SFR) indicators, using JWST photometry synthesized from Spitzer spectra of 49 low-redshift galaxies, which cover a wider luminosity range than most previous studies. We use Balmer-decrement-corrected Hα luminosity and synthesized MIR photometry to empirically calibrate the Spitzer, WISE, and JWST filters as SFR indicators. Our Spitzer and WISE calibrations are in good agreement with recent calibrations from the literature. While MIR luminosity may be directly proportional to SFR for high-luminosity galaxies, we find a power-law relationship between MIR luminosity and SFR for low-luminosity galaxies ({L}_{{H}α }≤slant {10}⁴³ {erg} {{{s}}}^-1). We find that for galaxies with an Hα luminosity of {10}⁴⁰ {erg} {{{s}}}^-1 (corresponding to an SFR of ∼ 0.055 {M}_⊙ {yr}}^-1), the corresponding JWST MIR ν L _ν luminosity is between 10^40.50 and {10}^41.00 {erg} {{{s}}}^-1. Power-law fits of JWST luminosity as a function of Hα luminosity have indices between 1.17 and 1.32. We find that the scatter in the JWST filter calibrations decreases with increasing wavelength from 0.39 to 0.20 dex, although F1000W is an exception where the scatter is just 0.24 dex.