Kavli Affiliate: Alexander P. Ji
| First 5 Authors: Harley Katz, Alexander P. Ji, O. Grace Telford, Peter Senchyna,
| Summary:
The first few cycles of JWST have identified an overabundance of UV-bright
galaxies and a general excess of UV luminosity density at $zgtrsim10$ compared
to expectations from most (pre-JWST) theoretical models. Moreover, some of the
brightest high-redshift spectroscopically confirmed galaxies exhibit peculiar
chemical abundance patterns, most notably extremely high N/O ratios. Since N/O
has been empirically shown to scale strongly with He/H, as expected for hot
hydrogen burning, these same bright high-redshift galaxies are likely also
helium-enhanced. Under simplistic assumptions for stellar evolution, the
bolometric luminosity of a star scales as $Lpropto
(4-frac{9}{2}Y+frac{5}{4}Y^{2})^{-1}$ — hence a higher He/H leads to
brighter stars. In this Letter, we evolve a series of MESA models to the
zero-age main-sequence and highlight that the helium enhancements at the levels
measured and inferred for high-redshift galaxies can boost the 1500
$mathring{rm A}$ UV luminosity by up to $sim50%$, while simultaneously
increasing the stellar effective temperature. The combination of helium
enhancements with nebular continuum emission expected for intense bursts of
star formation have the potential to help reduce the tension between JWST
observations and certain galaxy formation models.
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