Globular cluster progenitors may have been detected by HST , and are predicted to be observable with 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 JWST -NIRCam colour ( F 070 W - F 200 W ) , 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 .