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Abstract We report the discovery of 15 exceptionally luminous 10 ≲z≲ 14 candidate galaxies discovered in the first 0.28 deg2of JWST/NIRCam imaging from the COSMOS-Web survey. These sources span rest-frame UV magnitudes of −20.5 >MUV> −22, and thus constitute the most intrinsically luminousz≳ 10 candidates identified by JWST to date. Selected via NIRCam imaging, deep ground-based observations corroborate their detection and help significantly constrain their photometric redshifts. We analyze their spectral energy distributions using multiple open-source codes and evaluate the probability of low-redshift solutions; we conclude that 12/15 (80%) are likely genuinez≳ 10 sources and 3/15 (20%) likely low-redshift contaminants. Three of ourz∼ 12 candidates push the limits of early stellar mass assembly: they have estimated stellar masses ∼ 5 × 109M⊙, implying an effective stellar baryon fraction ofϵ⋆∼ 0.2−0.5, whereϵ⋆≡M⋆/(fbMhalo). The assembly of such stellar reservoirs is made possible due to rapid, burst-driven star formation on timescales < 100 Myr where the star formation rate may far outpace the growth of the underlying dark matter halos. This is supported by the similar volume densities inferred forM⋆∼ 1010M⊙galaxies relative toM⋆∼ 109M⊙—both about 10−6Mpc−3—implying they live in halos of comparable mass. At such high redshifts, the duty cycle for starbursts would be of order unity, which could cause the observed change in the shape of the UV luminosity function from a double power law to a Schechter function atz≈ 8. Spectroscopic redshift confirmation and ensuing constraints of their masses will be critical to understand how, and if, such early massive galaxies push the limits of galaxy formation in the Lambda cold dark matter paradigm.
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Evidence for a Shallow Evolution in the Volume Densities of Massive Galaxies at z = 4–8 from CEERS
Abstract We analyze the evolution of massive (log10[M⋆/M⊙] > 10) galaxies atz∼ 1–4 selected from JWST Cosmic Evolution Early Release Survey (CEERS). We infer the physical properties of all galaxies in the CEERS NIRCam imaging through spectral energy distribution (SED) fitting withdense basisto 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 WFSS. 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. We find that the evolving abundance of massive galaxies tracks expectations based on a constant baryon conversion efficiency in dark matter halos forz∼ 1–4. At higher redshifts, we observe an excess abundance of massive galaxies relative to this simple model, resulting in a shallower decline of observed volume densities of massive galaxies. 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.
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- PAR ID:
- 10536229
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astronomical Journal
- Volume:
- 168
- Issue:
- 3
- ISSN:
- 0004-6256
- Format(s):
- Medium: X Size: Article No. 113
- Size(s):
- Article No. 113
- Sponsoring Org:
- National Science Foundation
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