Pointing the James Webb Space Telescope through lensing clusters - can
  the first stars and galaxies be detected?
  The James Webb Space Telescope (JWST), scheduled for launch in 2014, is
expected to revolutionize our understanding of the high-redshift Universe. Even
so, many of the most interesting sources that may be hiding at redshifts z~10
(population III stars, dark stars, population III galaxies) are likely to be
intrinsically too faint for JWST. Here, we explore the prospects of searching
for the first stars and galaxies by pointing JWST through foreground lensing
clusters. Observations of this kind can reach significantly deeper than the
currently planned JWST ultra deep field in just a fraction of the exposure
time, but at the expense of probing a much smaller volume of the high-redshift
Universe. We also present Yggdrasil, a spectral synthesis code for modelling
the first galaxies, and use it to derive the masses of the faintest pop I, II
and III galaxies that can be detected through broadband imaging in JWST ultra
deep fields.
