We analyze the evolution of massive (log10​ [M⋆​/M⊙​] >10)
galaxies at z∼ 4--8 selected from the JWST Cosmic Evolution Early Release
Science (CEERS) survey. We infer the physical properties of all galaxies in the
CEERS NIRCam imaging through spectral energy distribution (SED) fitting with
dense basis to select a sample of high redshift massive galaxies. Where
available we include constraints from additional CEERS observing modes,
including 18 sources with MIRI photometric coverage, and 28 sources with
spectroscopic confirmations from NIRSpec or NIRCam wide-field slitless
spectroscopy. We sample the recovered posteriors in stellar mass from SED
fitting to infer the volume densities of massive galaxies across cosmic time,
taking into consideration the potential for sample contamination by active
galactic nuclei (AGN). We find that the evolving abundance of massive galaxies
tracks expectations based on a constant baryon conversion efficiency in dark
matter halos for z∼ 1--4. At higher redshifts, we observe an excess
abundance of massive galaxies relative to this simple model. These higher
abundances can be explained by modest changes to star formation physics and/or
the efficiencies with which star formation occurs in massive dark matter halos,
and are not in tension with modern cosmology.Comment: 20 pages, 10 figure