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The emergence of globular clusters and globular-cluster-like dwarfs

The emergence of globular clusters and globular-cluster-like dwarfs

2025AstrophysicsData Intensive Leicester

PI: Prof. Justin I. Read

In the EDGE project – Engineering Dwarfs at Galaxy Formation’s EDGE (dp324) – we simulate the smallest stellar systems at an unprecedented spatial resolution of just ~10 light years. At this resolution, we have resolved the formation of realistic, dense, globular star clusters through to the present day, in their full cosmological context, for the first time.

Published in Nature, our article shows how globulars form along multiple pathways while still looking similar observationally today. We also predict the existence of a new type of object that we call a “globular cluster-like dwarf” or “GCD”. GCDs are the first star systems to form in the Universe. Their dark matter halos are so low mass that their first supernovae are sufficient to shut down their star formation. This leaves a very distinctive observational fingerprint: an object with low stellar mass, small size, low metallicity, old age and very narrow age and metal spreads. In many ways, GCDs look like globular clusters. But in others – like their dark matter content – they look more like dwarf galaxies. Reviewing all known objects orbiting the Milky Way, we have already identified a number of candidate GCDs that may have been hiding in plain sight in our cosmic backyard.

Figure 1: A globular cluster (white object in the middle upper part of the frame) naturally emerges in an EDGE simulation of a dwarf galaxy.

If we can unambiguously prove the existence of GCDs, they will provide exciting new sites to explore the physics of the first stars, and unprecedented constraints on dark matter models.

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