摘要
We present results from the Cosmic Evolution Early Release Survey (CEERS) on the stellar-population parameters for 28 galaxies with redshifts$4<z<9$using imaging data from the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) combined with data from the Hubble Space Telescope and the Spitzer Space Telescope. The JWST/MIRI 5.6 and 7.7$\mu$ m data extend the coverage of the rest-frame spectral-energy distribution (SED) to nearly 1 micron for galaxies in this redshift range. By modeling the galaxies' SEDs the MIRI data show that the galaxies have, on average, rest-frame UV (1600 A)$-$$I$ -band colors 0.4 mag bluer than derived when using photometry that lacks MIRI. Therefore, the galaxies have lower (stellar)-mass-to-light ratios. The MIRI data reduce the stellar masses by$\langle \Delta\log M_\ast\rangle=0.25$dex at$4<z<6$(a factor of 1.8) and 0.37 dex at$6<z<9$(a factor of 2.3). This also reduces the star-formation rates (SFRs) by$\langle \Delta\log\mathrm{SFR} \rangle=0.14$dex at$4<z<6$and 0.27 dex at$6<z<9$ . The MIRI data also improve constraints on the allowable stellar mass formed in early star-formation. We model this using a star-formation history that includes both a "burst' at$z_f=100$and a slowly varying ("delayed- $\tau$ ") model. The MIRI data reduce the allowable stellar mass by 0.6 dex at$4<z< 6$and by$\approx$ 1 dex at$6<z<9$ . Applying these results globally, this reduces the cosmic stellar-mass density by an order of magnitude in the early universe ( $z\approx9$ ). Therefore, observations of rest-frame$\gtrsim$ 1$\mu$ m are paramount for constraining the stellar-mass build-up in galaxies at very high-redshifts.