Kavli Affiliate: Mark Vogelsberger
| First 5 Authors: Xuejian Shen, Mark Vogelsberger, Michael Boylan-Kolchin, Sandro Tacchella, Rohan P. Naidu
| Summary:
JWST has revealed a large population of ultra-violet (UV)-bright galaxies at
$zgtrsim 10$ and possibly overly massive galaxies at $zgtrsim 7$, challenging
standard galaxy formation models in the $Lambda$CDM cosmology. We use an
empirical galaxy formation model to explore the potential of alleviating these
tensions through an Early Dark Energy (EDE) model, originally proposed to solve
the Hubble tension. Our benchmark model demonstrates excellent agreement with
the UV luminosity functions (UVLFs) at $4lesssim z lesssim10$ in both
$Lambda$CDM and EDE cosmologies. In the EDE cosmology, the UVLF measurements
at $zsimeq 12$ based on spectroscopically confirmed galaxies exhibit no
tension with the benchmark model. Photometric constraints at $12 lesssim
zlesssim 16$ can be fully explained within EDE via either moderately increased
star formation efficiencies ($epsilon_{ast}sim 3-10%$ at $M_{rm halo}sim
10^{10.5},{rm M}_odot$) or enhanced UV variabilities ($sigma_{rm UV}sim
0.8-1.3$ mag at $M_{rm halo}sim 10^{10.5},{rm M}_odot$) that are within
the scatter of hydrodynamical simulation predictions. A similar agreement is
difficult to achieve in $Lambda$CDM, especially at $zgtrsim 14$, where the
required $sigma_{rm UV}$ exceeds the maximum value seen in simulations.
Furthermore, the implausibly large cosmic stellar mass densities inferred from
some JWST observations are no longer in tension with cosmology when the EDE is
considered. Our findings highlight EDE as an intriguing unified solution to a
fundamental problem in cosmology and the recent tensions raised by JWST
observations. Data at the highest redshifts reached by JWST ($z sim 14-16$)
will be crucial for differentiating modified galaxy formation physics from new
cosmological physics.
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