Early Results from GLASS-JWST. XI. Stellar Masses and Mass-to-light Ratio of z > 7 Galaxies
P. Santini, A. Fontana, M. Castellano, Nicha Leethochawalit, Michele Trenti, Tommaso Treu, Davide Belfiori, Simon Birrer, Andrea Bonchi, E. Merlin, Charlotte Mason, Takahiro Morishita, M. Nonino, D. Paris, G. Polenta, P. Rosati, Lilan Yang, Kristan Boyett, Maruša Bradač, Antonello Calabrò, Alan Dressler, Karl Glazebrook, Danilo Marchesini, Sara Mascia, Themiya Nanayakkara, L. Pentericci, Guido Roberts-Borsani, Claudia Scarlata, Benedetta Vulcani, Xin Wang
Abstract
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.