Abstract
Globular clusters (GCs) are amongst the oldest and densest stellar systems in the
Universe, yet how they form remains an enduring puzzle. In this thesis, I present
a suite of state-of-the-art cosmological simulations in which both dark matter-free
GCs and dark matter rich dwarf galaxies naturally emerge in the Standard
Cosmology. I show that these objects inhabit distinct locations in the size-luminosity
plane and that they have a similar ages, age-spread, metallicity and metallicity-spread
to GCs and dwarfs in the nearby Universe. About half of the simulated
GCs form via regular star formation within their host dwarf, with the rest forming
further out, triggered by mergers. These latter are more tidally isolated and more
likely to survive through to the present day. I verify this with detailed follow-up
simulations using a more accurate direct N-body code. I find that even more GCs
survive when properly modelling such two-body effects, and that they can tidally
evolve into extreme regions of the size-luminosity plane (MV > −2) occupied by
currently unclassified objects. If these unclassified objects are tidally disrupting
GCs, then I predict that they will have high metallicity ([Fe/H] > −2), with a low
metallicity-spread of < 0.2 dex. Finally, my simulations predict the existence of a
new class of object that I call ‘globular cluster-like dwarfs’ (GCDs). These form
from a single, self-quenching, star formation event in low mass dark matter halos
at high redshift and have observational properties that are intermediate between
globulars and dwarfs. I discuss whether GCDs could be hiding in plain sight in our
cosmic backyard, and how they can be harnessed to probe the nature of dark matter
and hunt for metal-free stars.