  We present high resolution submillimeter interferometric imaging of two of
the brightest high-redshift submillimeter galaxies known: GN20 and AzTEC1 at
0.8 and 0.3 arcsec resolution respectively. Our data - the highest resolution
submillimeter imaging of high redshift sources accomplished to date - was
collected in three different array configurations: compact, extended, and very
extended. We derive angular sizes of 0.6 and 1.0 arcsec for GN20 and 0.3 and
0.4 arcsec for AzTEC1 from modeling their visibility functions as a Gaussian
and elliptical disk respectively. Because both sources are B-band dropouts,
they likely lie within a relatively narrow redshift window around z~4, which
indicates their angular extent corresponds to physical scales of 4-8 and 1.5-3
kpc respectively for the starburst region. By way of a series of simple
assumptions, we find preliminary evidence that these hyperluminous starbursts -
with star formation rates >1000 $M_\odot$ yr$^{-1}$ - are radiating at or close
to their Eddington limit. Should future high resolution observations indicate
that these two objects are typical of a population of high redshift
Eddington-limited starbursts, this could have important consequences for models
of star formation and feedback in extreme environments.
