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Globular cluster progenitors may have been detected by \textit{HST}, and arepredicted to be observable with \textit{JWST} and ground-based extremely-largetelescopes with adaptive optics. This has the potential to elucidate the issueof globular cluster formation and the origins of significantly helium-enrichedsubpopulations, a problem in Galactic astronomy with no satisfactorytheoretical solution. Given this context, we use model stellar tracks andisochrones to investigate the predicted observational properties ofhelium-enriched stellar populations in globular cluster progenitors. We findthat, relative to helium-normal populations, helium-enriched(${\Delta}Y=+0.12$) stellar populations similar to those inferred in the mostmassive globular clusters, are expected, modulo some rapid fluctuations in thefirst $\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 toconverge 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 uphigher for helium-enriched stars.

The Predicted Properties of Helium-Enriched Globular Cluster Progenitors at High Redshift