Description
The identification of young massive star clusters (YMCs) at cosmological distance
is becoming a real fact. The occurrence of such systems is believed to increase at
high redshift, eventually enclosing a significant fraction of the star formation activity
of the Universe, in an epoch when also globular clusters (GC) formed. The potential role
of such stellar systems play during reionization, their demography and the physical
mechanisms behind the formation of GCs are among the key questions that will require
JWST and E-ELT for a crucial quantum leap. I'll present recent results from Hubble deep
imaging coupled with our VLT/MUSE Deep Lensed Field (MDLF, 20 h) and VLT/X-Shooter
observations boosted by strong gravitational lensing. The best cosmic lenses allow us
to anticipate E-ELT high spatial resolution capabilities (a few mas) and probe new
low-luminosity regimes (mag > 32), along with quantifying our current limitations when
studying non-lensed sources. The same cosmic lenses observed with E-ELT will allow us
to further probe star-formation at the pc scale (or sub-pc in the more extreme cases),
and identify gravitationally-bound star clusters in the first Gyrs, possibly GC precursors.
