The Predicted Properties of Helium-Enriched Globular Cluster Progenitors
  at High Redshift
  Globular cluster progenitors may have been detected by \textit{HST}, and are
predicted to be observable with \textit{JWST} and ground-based extremely-large
telescopes with adaptive optics. This has the potential to elucidate the issue
of globular cluster formation and the origins of significantly helium-enriched
subpopulations, a problem in Galactic astronomy with no satisfactory
theoretical solution. Given this context, we use model stellar tracks and
isochrones to investigate the predicted observational properties of
helium-enriched stellar populations in globular cluster progenitors. We find
that, relative to helium-normal populations, helium-enriched
(${\Delta}Y=+0.12$) stellar populations similar to those inferred in the most
massive globular clusters, are expected, modulo some rapid fluctuations in the
first $\sim$30 Myr, to be brighter and redder in the rest frame. At fixed age,
stellar mass, and metallicity, a helium-enriched population is predicted to
converge to being $\sim$0.40 mag brighter at $\lambda \approx 2.0\, {\mu}m$,
and to be 0.30 mag redder in the \textit{JWST}-NIRCam colour $(F070W-F200W)$,
and to actually be fainter for $\lambda \lesssim 0.50 \, {\mu}m$. Separately,
we find that the time-integrated shift in ionizing radiation is a negligible
$\sim 5\%$, though we show that the Lyman-$\alpha$ escape fraction could end up
higher for helium-enriched stars.
