Detection of isolated population III stars with the James Webb Space
  Telescope
  The first population III stars are predicted to form in minihalos at a
redshift of approximately 10-30. The James Webb Space Telescope (JWST),
tentatively scheduled for launch in 2018, will probably be able to detect some
of the first galaxies, but whether it will also be able to detect the first
stars remains more doubtful. Here, we explore the prospects of detecting an
isolated population III star or a small cluster of population III stars down to
redshift 2 in either lensed or unlensed fields. Our calculations are based on
realistic stellar atmospheres and take into account the potential flux
contribution from the surrounding HII region. We find that unlensed population
III stars are beyond the reach of JWST, and that even lensed population III
stars will be extremely difficult to detect. However, the main problem with the
latter approach is not necessarily that the lensed stars are too faint, but
that their surface number densities are too low. To detect even one population
III star of 60 solar masses when pointing JWST through the galaxy cluster MACS
J0717.5+3745, the lensing cluster with the largest Einstein radius detected so
far, the cosmic star formation rate of population III stars would need to be
approximately an order of magnitude higher than predicted by the most
optimistic current models.
