Science with an ngVLA: New Parameter Space for Deep Field Radio
  Continuum Surveys
  Deep continuum surveys at radio wavelengths are able to cover large areas,
yield high angular resolution, and do not suffer from dust extinction, thus
providing a robust way to measure the star formation history of the universe.
However, with the current sensitivities of existing radio telescopes, it
remains challenging to detect galaxies that dominate the cosmic star formation
history even with extremely long integrations. With the ngVLA, a new portion of
parameter space will be opened up for radio continuum surveys: deep (~200
nJy/bm), large-area (~1 deg^2), sub-arcsecond surveys at high frequencies (~8
GHz), where the observed radio emission from high-z galaxies should be
dominated by free-free emission, providing a robust measurement for the star
formation history of the universe. By being able to image the star formation
activity, unbiased by dust, for a large, homogeneous sample of galaxies with a
wide range of luminosities into the epoch of reionization, such surveys with
the ngVLA will be highly complementary to those conducted by JWST, which will
only be sensitive to un-obscured star formation.
