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

Globular cluster progenitors may have been detected by Hubble Space Telescope, and are predicted to be observable with James Webb Space Telescope (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 usemodel 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 similar to 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 similar to 0.40 mag brighter at lambda approximate to 2.0 mu m, and to be 0.30-mag redder in the JWST-NIRCam colour (F070W - F200W), and to actually be fainter for lambda approximate to 0.50 mu m. Separately, we find that the time-integrated shift in ionizing radiation is a negligible similar to 5 per cent, though we show that the Lyman-alpha escape fraction could end up higher for helium-enriched stars.