Insights from HST into Ultramassive Galaxies and Early-Universe Cosmology.

Phys Rev Lett

William H. Miller III Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, USA.

Published: February 2024

The early-science observations made by the James Webb Space Telescope (JWST) have revealed an excess of ultramassive galaxy candidates that appear to challenge the standard cosmological model (ΛCDM). Here, we argue that any modifications to ΛCDM that can produce such ultramassive galaxies in the early Universe would also affect the UV galaxy luminosity function (UV LF) inferred from the Hubble Space Telescope (HST). The UV LF covers the same redshifts (z≈7-10) and host-halo masses (M_{h}≈10^{10}-10^{12}M_{⊙}) as the JWST candidates, but tracks star-formation rate rather than stellar mass. We consider beyond-ΛCDM power-spectrum enhancements and show that any departure large enough to reproduce the abundance of ultramassive JWST candidates is in conflict with the HST data. Our analysis, therefore, severely disfavors a cosmological explanation for the JWST abundance problem. Looking ahead, we determine the maximum allowable stellar-mass function and provide projections for the high-z UV LF given our constraints on cosmology from current HST data.

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http://dx.doi.org/10.1103/PhysRevLett.132.061002DOI Listing

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Article Synopsis
  • Recent observations from the James Webb Space Telescope (JWST) have found many massive-galaxy candidates in the early Universe, stretching further back in time and at lower brightness levels than previously seen.
  • These findings initially posed challenges to the Λ cold dark-matter model, but the new study's results show no significant conflicts when accounting for spectroscopic redshifts.
  • The research highlights three ultra-massive galaxies that convert a notably high percentage of baryons into stars, suggesting they play a significant role in cosmic star-formation rates at redshifts 5 to 6.
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Insights from HST into Ultramassive Galaxies and Early-Universe Cosmology.

Phys Rev Lett

February 2024

William H. Miller III Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, USA.

The early-science observations made by the James Webb Space Telescope (JWST) have revealed an excess of ultramassive galaxy candidates that appear to challenge the standard cosmological model (ΛCDM). Here, we argue that any modifications to ΛCDM that can produce such ultramassive galaxies in the early Universe would also affect the UV galaxy luminosity function (UV LF) inferred from the Hubble Space Telescope (HST). The UV LF covers the same redshifts (z≈7-10) and host-halo masses (M_{h}≈10^{10}-10^{12}M_{⊙}) as the JWST candidates, but tracks star-formation rate rather than stellar mass.

View Article and Find Full Text PDF

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