Early Results from GLASS-JWST. XI. Stellar Masses and Mass-to-light Ratio of z > 7 Galaxies
Polenta, G.; Vulcani, B.; Treu, T.; Castellano, M.; Pentericci, L.; Trenti, M.; Rosati, P.; Santini, P.; Merlin, E.; Fontana, A.; Marchesini, D.; Scarlata, C.; Glazebrook, K.; Wang, Xin; Nonino, M.; Nanayakkara, T.; Calabrò, A.; Morishita, T.; Dressler, A.; Yang, L.; Mason, C.; Boyett, K.; Bradac, M.; Paris, D.; Mascia, S.; Leethochawalit, N.; Roberts-Borsani, G.; Bonchi, A.; Birrer, S.; Belfiori, D.
Italy, Australia, Thailand, United States, Denmark, Japan, Slovenia
Abstract
We exploit James Webb Space Telescope (JWST) NIRCam observations from the GLASS-JWST-Early Release Science program to investigate galaxy stellar masses at z > 7. We first show that JWST observations reduce the uncertainties on the stellar mass by a factor of at least 5-10, when compared with the highest-quality data sets available to date. We then study the UV mass-to-light ratio, finding that galaxies exhibit a a two orders of magnitude range of M/L UV values for a given luminosity, indicative of a broad variety of physical conditions and star formation histories. As a consequence, previous estimates of the cosmic stellar-mass density-based on an average correlation between UV luminosity and stellar mass-can be biased by as much as a factor of ~6. Our first exploration demonstrates that JWST represents a new era in our understanding of stellar masses at z > 7 and, therefore, of the growth of galaxies prior to cosmic reionization.