The Star-forming and Ionizing Properties of Dwarf Reionization-Era Galaxies

In the decade leading up to JWST, dedicated observations with Spitzer/IRAC revealed that the brightest reionization-era galaxies often exhibit young ages and strong nebular line emission, hinting at high ionizing efficiency among early galaxies. However, IRAC’s poor sensitivity stifled efforts to study the fainter, more numerous z>6 population often thought largely responsible for reionization. In this talk, we present the first detailed statistical analysis of the star-forming and ionizing properties of UV-faint (-20 < Muv < -16.5) z~6-9 galaxies using the immensely improved sensitivity and rich SED sampling of JADES/NIRCam data. We briefly introduce the diversity of galaxy SEDs among our sample of approximately 700 objects, commenting on the range of light-weighted ages, stellar masses, nebular emission line strengths, and dust attenuation strengths inferred among this sample. We then discuss what our results may imply for the ionizing efficiency of very faint (Muv > -18) reionization-era galaxies relative to the brighter population (Muv ~ -20). Finally, we describe potential evidence for bursty star formation histories among the sample and comment on possible implications during both reionization and cosmic dawn.