2017MNRAS.469L..63R

The formation of globular clusters (GCs) with their multiple stellar populations remains a puzzling, unsolved problem in astrophysics. One way to gather critical insight consists in finding sizable numbers of GC progenitors (GCPs) while still near the peak of their star formation phase, at a look-back time corresponding to GC ages (∼12.5 Gyr, or z ≃ 5). This opportunity is quantitatively explored, calculating how many GCPs could be detected by deep imaging in the optical, near-IR and mid-IR bands. For concreteness, for the imaging camera performances those of NIRCam on board of James Webb Space Telescope are adopted. The number of GCPs that could be detected scales linearly with their mass, i.e. on how much more massive GCPs were compared to their GC progeny, and perspectives look promising. Besides providing direct evidence on GC formation, the detection of GCPs, their clustering, with or without a central galaxy already in place, would shed light on the relative timing of GC formation and galaxy growth and assembly. All this may be the result of dedicated observations as well as a side benefit of deep imaging meant to search for the agents of cosmic reionization.