Abstract
The early release science results from the $James Webb Space
Telescope (JWST)$ have yielded an unexpected abundance of high-redshift
luminous galaxies that seems to be in tension with current theories of galaxy
formation. However, it is currently difficult to draw definitive conclusions
form these results as the sources have not yet been spectroscopically
confirmed. It is in any case important to establish baseline predictions from
current state-of-the-art galaxy formation models that can be compared and
contrasted with these new measurements. In this work, we use the new
large-volume ($L_box740 \, cMpc$) hydrodynamic
simulation of the MilleniumTNG project to make predictions for the
high-redshift ($z\gtrsim8$) galaxy population and compare them to recent
$JWST$ observations. We show that the simulated galaxy population is
broadly consistent with observations until $z\sim10$. From $z\approx10-12$, the
observations indicate a preference for a galaxy population that is largely
dust-free, but is still consistent with the simulations. Beyond $z\gtrsim12$,
however, our simulation results underpredict the abundance of luminous galaxies
and their star-formation rates by almost an order of magnitude. This indicates
either an incomplete understanding of the new $JWST$ data or a need
for more sophisticated galaxy formation models that account for additional
physical processes such as Population~III stars, variable stellar initial mass
functions, or even deviations from the standard $Łambda$CDM model. We
emphasise that any new process invoked to explain this tension should only
significantly influence the galaxy population beyond $z\gtrsim10$, while
leaving the successful galaxy formation predictions of the fiducial model
intact below this redshift.
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