SANTINI, PaolaPaolaSANTINIA. FontanaM. CastellanoN. LeethochawalitM. TrentiT. TreuD. BelfioriS. BirrerA. BonchiE. MerlinC. MasonT. MorishitaM. NoninoD. ParisG. PolentaP. RosatiL. YangK. BoyettM. BradacA. CalabròA. DresslerK. GlazebrookD. MarchesiniS. MasciaT. NanayakkaraL. PentericciG. Roberts-BorsaniC. ScarlataB. VulcaniXin Wang2025-03-102025-03-1020232041-8205http://hdl.handle.net/20.500.12386/36593We 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.STAMPAenArticle10.3847/2041-8213/ac95862-s2.0-85146381911https://doi.org/10.3847/2041-8213/ac9586https://iopscience.iop.org/article/10.3847/2041-8213/ac95862023ApJ...942L..27SFIS/05 - ASTRONOMIA E ASTROFISICA