  Using a combination of radio and optical imaging at 0.1\arcs to 0.2\arcs
resolution with the VLA/MERLIN and HST has led to a breakthrough in our
understanding of radio emission from distant (0.1<z<3) starburst galaxies. We
have recently isolated a number of high redshift, dusty starburst galaxies that
remain invisible in ground based images to I_{AB}=25 and I_{AB}=28.5 in the
Hubble Deep Field. These galaxies appear as faint radio sources, often
accompanied by very red counterparts (I-K > 4-6) and submillimeter sources with
S > 2 mJy at 850 microns as measured with SCUBA on the JCMT. The far-infrared
luminosities of these galaxies exceeds even the most intense starbursts found
in the local universe (e.g., Arp 220), suggesting they are in the process of
converting the bulk of their gass mass into stars.
  These galaxies, completely absent in optical surveys, constitute 50% - 90% of
the star-formation density in the distant Universe. Given the poor sub-mm
resolution (15\arcs) of the SCUBA/JCMT images, we use the 0.2\arcs radio
imaging as a surrogate in order to understand the nature of the dominant
emission mechanism driving the FIR luminosity (AGN vs. star-formation).
Upcoming developments in radio instrumentation (the Expanded VLA Array and
Square Kilometer Array) will soon increase sensitivity and resolution orders of
magnitude, providing a natural complement to parallel developments in sub-mm
facilities (e.g., ALMA). With dual radio continuum and sub-mm surveys of the
distant Universe, a census of galaxy evolution to the earliest cosmic epochs (z
= 5-30) will soon be possible.
