Linking globular cluster formation at low and high redshift through the
  age-metallicity relation in E-MOSAICS
  We set out to compare the age-metallicity relation (AMR) of massive clusters
from Magellanic Cloud mass galaxies in the E-MOSAICS suite of numerical
cosmological simulations with an amalgamation of observational data of massive
clusters in the Large and Small Magellanic Clouds (LMC/SMC). We aim to test if:
i) star cluster formation proceeds according to universal physical processes,
suggestive of a common formation mechanism for young-massive clusters (YMCs),
intermediate-age clusters (IACs), and ancient globular clusters (GCs); ii)
massive clusters of all ages trace a continuous AMR; iii) the AMRs of smaller
mass galaxies show a shallower relation when compared to more massive galaxies.
Our results show that, within the uncertainties, the predicted AMRs of
L/SMC-mass galaxies with similar star formation histories to the L/SMC follow
the same relation as observations. We also find that the metallicity at which
the AMR saturates increases with galaxy mass, which is also found for the field
star AMRs. This suggests that relatively low-metallicity clusters can still
form in dwarfs galaxies. Given our results, we suggest that ancient GCs share
their formation mechanism with IACs and YMCs, in which GCs are the result of a
universal process of star cluster formation during the early episodes of star
formation in their host galaxies.
