Probing Star Formation at Low Metallicity: The Radio Emission of Super
  Star Clusters in SBS0335-052
  We present high-resolution radio continuum observations of the nascent
starburst in the metal-poor galaxy SBS 0335-052. These radio data were taken
with the Very Large Array and include observations at 0.7cm, 1.3cm, 2cm, 3.6cm,
and 6cm. These observations enable us to probe the thermal radio nebulae
associated with the extremely young star-forming regions in this galaxy. Two
discrete and luminous star-forming regions are detected in the south of the
galaxy that appear to be associated with massive star clusters previously
identified at optical wavelengths. However, the remaining optically-identified
massive star clusters are not clearly associated with radio emission (either
thermal or non-thermal) down to the sensitivity limits of these radio data. The
spectral energy distributions of the two radio-detected clusters are consistent
with being purely thermal, and the entire region has an inferred ionizing flux
of ~1.2 x 10^ 53 s^-1, which is equivalent to ~12,000 "typical" O-type stars
(type O7.5 V). The observations presented here have resolved out a significant
contribution from diffuse non-thermal emission detected previously, implying a
previous episode of significant star formation. The current star formation rate
(SFR) for this southern region alone is ~1.3 M_sun yr^-1, or ~ 23M_sun yr^-1
kpc^-2. This SFR derived from thermal radio emission also suggests that
previous optical recombination line studies are not detecting a significant
fraction of the current star formation in SBS 0335-052. From model fits to the
radio spectral energy distribution, we infer a global mean density in the two
youngest clusters of n_e > 10^3-10^4 cm^-3. In addition, a comparison between
the compact and diffuse radio emission indicates that up to ~50% of the
ionizing flux could be leaking out of the compact HII regions.
