Date: 9/22/2024
Harvard ADS: Early galaxies and early dark energy: a unified solution to the hubble tension and puzzles of massive bright galaxies revealed by JWST
Paper abstract: JWST has revealed a large population of UV-bright galaxies at z\gtrsim 10 and possibly overly massive galaxies at z\gtrsim 7, challenging standard galaxy formation models in the ?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 4<~ z <~ 10 in both ?CDM and EDE cosmologies. In the EDE cosmology, the UVLF measurements at z~eq 12 based on spectroscopically confirmed galaxies (eight galaxies at z~eq 11\!-\!13.5) exhibit no tension with the benchmark model. Photometric constraints at 12 <~ z<~ 16 can be fully explained within EDE via either moderately increased star-formation efficiencies (\epsilon _{\ast}~ 3\!-\!10\ \hbox{per cent} at M_{\rm halo}~ 10^{10.5}{\, \rm M_\odot }) or enhanced UV variabilities (\sigma _{\rm UV}~ 0.8\!-\!1.3 mag at M_{\rm halo}~ 10^{10.5}{\, \rm M_\odot }) that are within the scatter of hydrodynamical simulation predictions. A similar agreement is difficult to achieve in \LambdaCDM, especially at z\gtrsim 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 will be crucial for differentiating modified galaxy formation physics from new cosmological physics.
