Formation of proto-globular cluster candidates in cosmological
  simulations of dwarf galaxies at $z>4$
  We perform cosmological hydrodynamical simulations to study the formation of
proto-globular cluster candidates in progenitors of present-day dwarf galaxies
$(M_{\rm vir} \approx 10^{10}\, {\rm M}_\odot$ at $z=0$) as part of the
"Feedback in Realistic Environment" (FIRE) project. Compact ($r_{1/2}<30$ pc),
relatively massive ($0.5 \times 10^5 \lesssim M_{\star}/{\rm M}_\odot \lesssim
5\times10^5$), self-bound stellar clusters form at $11\gtrsim z \gtrsim 5$ in
progenitors with $M_{\rm vir} \approx 10^9\,{\rm M}_\odot$. Cluster formation
is triggered when at least $10^7\,{\rm M}_\odot$ of dense, turbulent gas
reaches $\Sigma_{\rm gas} \approx 10^4\, {\rm M}_\odot\, {\rm pc}^{-2}$ as a
result of the compressive effects of supernova feedback or from cloud-cloud
collisions. The clusters can survive for $2-3\,{\rm Gyr}$; 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 \textit{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 \textit{James Webb Space Telescope}. By contrast,
the star clusters' host galaxies will remain undetectable.
