Calzetti, DanielaAdamo, AngelaLinden, Sean T.Gregg, BenjaminKrumholz, Mark R.Bajaj, VarunBik, ArjanCignoni, MicheleCorrenti, MatteoElmegreen, BruceFaustino Vieira, HelenaGallagher, John S.Grasha, KathrynGutermuth, Robert A.Johnson, Kelsey E.Messa, MatteoMelinder, JensÖstlin, GöranPedrini, AlexSabbi, ElenaSmith, Linda J.Tosi, Monica2025-05-232025-05-230004-637XORCID:/0000-0003-3893-854X/work/184099305ORCID:/0000-0002-3247-5321/work/184104080http://www.scopus.com/inward/record.url?scp=85201096999&partnerID=8YFLogxKhttps://hdl.handle.net/1885/733752681New JWST near-infrared imaging of the nearby galaxy NGC 628 from the JWST Cycle 1 program Feedback in Emerging extrAgalactic Star clusTers (JWST-FEAST) is combined with archival JWST mid-infrared imaging to calibrate the 21 μm emission as a star formation rate (SFR) indicator at ∼120 pc scales. The Paα (1.8756 μm) hydrogen recombination emission line targeted by FEAST provides a reference SFR indicator that is relatively insensitive to dust attenuation, as demonstrated by combining this tracer with Hubble Space Telescope Hα imaging. Our analysis is restricted to regions that appear compact in nebular line emission and are sufficiently bright to mitigate effects of both age and stochastic sampling of the stellar initial mass function. We find that the 21 μm emission closely correlates with the nebular line emission, with a power law with exponent = 1.07 ± 0.01, in agreement with past results. We calibrate a hybrid SFR indicator using a combination of Hα and 24 μm (extrapolated from 21 μm) tracers and derive the proportionality constant between the two tracers, b = 0.095 ± 0.007, which is ∼3-5 times larger than previous derivations using large regions/entire galaxies. We model these discrepancies as an increasing contribution to the dust heating by progressively older stellar populations for increasing spatial scale, in agreement with earlier findings that star formation is hierarchically distributed in galaxies. Thus, the use of hybrid SFR indicators requires prior knowledge of the mean age of the stellar populations dominating the dust heating, which makes their application uncertain. Conversely, nonlinear calibrations of SFRs from L(24) alone are more robust, with a factor ≲ 2.5 variation across the entire range of L(24) luminosities from H ii regions to galaxies.This work is based in part on observations made with the NASA/ESA/CSA James Webb Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127. These observations are associated with program #1783. Support for program #1783 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127. K.G. is supported by the Australian Research Council through the Discovery Early Career Researcher Award (DECRA) Fellowship (project number DE220100766) funded by the Australian Government and by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. M.R.K. acknowledges support from the Australian Research Council through Laureate Fellowship FL220100020. A.A. and A.P. acknowledge support from the Swedish National Space Agency (SNSA) through grant 2021-00108.enPublisher Copyright: © 2024. The Author(s). Published by the American Astronomical Society.2024-08-0110.3847/1538-4357/ad53c085201096999