Low-mass Globular Clusters from Stripped Dark Matter Halos

The origin and formation of globular clusters (GCs) has remained a mystery. We present a formation scenario for ancient GC-like objects that form in ultrahigh-resolution simulations (smallest cell size < 0.1 pc, mass resolution M cell = 4 M ⊙ ). The simulations are cosmological zoom-in simulations of dwarf galaxies within the stellar mass range 10 6−7 M ⊙ that match Local Group dwarf properties well. Our investigation reveals GCs hosting ancient stellar populations, characterized by a lack of dark matter (DM) in the present epoch. The clusters exhibit short, episodic star formation histories, occasionally marked by the presence of multiple stellar generations. The metallicity distributions show a widening, encompassing stars in the range of 10 −4 < Z ⋆ / Z ⊙ < 1. The presence of these objects is attributable to star formation occurring within low-mass DM halos ( M halo ≈ 10 6 M ⊙ ) during the early stages of the Universe, preceding reionization ( z ≳ 7). As these clusters are accreted into dwarf galaxies, DM is preferentially subjected to tidal stripping, with an average accretion redshift of z ¯ ≈ 5 .