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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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Inferred galaxy properties during Cosmic Dawn from early JWST photometry results
ABSTRACT Early photometric results from JWST have revealed a number of galaxy candidates above redshift 10. The initial estimates of inferred stellar masses and the associated cosmic star formation rates are above most theoretical model predictions up to a factor of 20 in the most extreme cases, while this has been moderated after the recalibration of NIRCam and subsequent spectroscopic detections. Using these recent JWST observations, we use galaxy scaling relations from cosmological simulations to model the star formation history to very high redshifts, back to a starting halo mass of 107 M⊙, to infer the intrinsic properties of the JWST galaxies. Here, we explore the contribution of supermassive black holes, stellar binaries, and an excess of massive stars to the overall luminosity of high-redshift galaxies. Despite the addition of alternative components to the spectral energy distribution, we find stellar masses equal to or slightly higher than previous stellar mass estimates. Most galaxy spectra are dominated by the stellar component, and the exact choice for the stellar population model does not appear to make a major difference. We find that four of the 12 high-redshift galaxy candidates are best fit with a non-negligible active galactic nuclei component, but the evidence from the continuum alone is insufficient to confirm their existence. Upcoming spectroscopic observations of z > 10 galaxies will confirm the presence and nature of high-energy sources in the early Universe and will constrain their exact redshifts.
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- Award ID(s):
- 1835213
- PAR ID:
- 10458587
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 525
- Issue:
- 3
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 4405-4425
- Size(s):
- p. 4405-4425
- Sponsoring Org:
- National Science Foundation
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