Observational Signatures of the First Galaxies
  Detection of the radiation emitted from some of the earliest galaxies will be
made possible in the next decade, with the launch of the James Webb Space
Telescope (JWST). A significant fraction of these galaxies may host Population
(Pop) III star clusters. The detection of the recombination radiation emitted
by such clusters would provide an important new constraint on the initial mass
function (IMF) of primordial stars. Here I review the expected recombination
line signature of Pop III stars, and present the results of cosmological
radiation hydrodynamics simulations of the initial stages of Pop III starbursts
in a first galaxy at z ~ 12, from which the time-dependent luminosities and
equivalent widths of IMF-sensitive recombination lines are calculated. While it
may be unfeasible to detect the emission from Pop III star clusters in the
first galaxies at z > 10, even with next generation telescopes, Pop III star
clusters which form at lower redshifts (i.e. at z < 6) may be detectable in
deep surveys by the JWST.
