Sameie et al., available on arXiv

Abstract: We perform cosmological hydrodynamical simulations to study the formation of proto-globular cluster candidates in progenitors of present-day dwarf galaxies (Mvir~10^10 Msun at z=0) as part of the “Feedback in Realistic Environment” (FIRE) project. Compact (r1/2<30 pc), relatively massive (0.5*10^5<~Mstar/Msun<~5*10^5), self-bound stellar clusters form at 11>~z>~5 in progenitors with Mvir~10^9 Msun. Cluster formation is triggered when at least 10^7 Msun of dense, turbulent gas reaches Sigma_gas~10^4 Msun pc^−2 as a result of the compressive effects of supernova feedback or from cloud-cloud collisions. The clusters can survive for 2−3Gyr; absent numerical effects, they would likely survive substantially longer, perhaps to z=0. The longest-lived clusters are those that form at significant distance — several hundreds of pc — from their host galaxy. We therefore predict that globular clusters forming in progenitors of present-day dwarf galaxies will be offset from any pre-existing stars within their host dark matter halos as opposed to deeply embedded within a well-defined galaxy. Properties of the nascent clusters are consistent with observations of some of the faintest and most compact high-redshift sources in Hubble Space Telescope lensing fields and are at the edge of what will be detectable as point sources in deep imaging of non-lensed fields with the James Webb Space Telescope. By contrast, the star clusters’ host galaxies will remain undetectable.