Deviations from the Infrared-Radio Correlation in Massive, Ultra-compact
  Starburst Galaxies
  Feedback through energetic outflows has emerged as a key physical process
responsible for transforming star-forming galaxies into the quiescent systems
observed in the local universe. To explore this process, this paper focuses on
a sample of massive and compact merger remnant galaxies hosting high-velocity
gaseous outflows ($|v| \gtrsim 10^{3}$ km s$^{-1}$), found at intermediate
redshift ($z \sim 0.6$). From their mid-infrared emission and compact
morphologies, these galaxies are estimated to have exceptionally large star
formation rate (SFR) surface densities ($\Sigma_{SFR} \sim 10^{3}$
$\mathrm{M_{\odot}}$ yr$^{-1}$ kpc$^{-2}$), approaching the Eddington limit for
radiation pressure on dust grains. This suggests that star formation feedback
may be driving the observed outflows. However, these SFR estimates suffer from
significant uncertainties. We therefore sought an independent tracer of star
formation to probe the compact starburst activity in these systems. In this
paper, we present SFR estimates calculated using 1.5 GHz continuum Jansky Very
Large Array observations for 19 of these galaxies. We also present updated
infrared (IR) SFRs calculated from WISE survey data. We estimate SFRs from the
IR to be larger than those from the radio for 16 out of 19 galaxies by a median
factor of 2.5. We find that this deviation is maximized for the most compact
galaxies hosting the youngest stellar populations, suggesting that compact
starbursts deviate from the IR-radio correlation. We suggest that this
deviation stems either from free-free absorption of synchrotron emission, a
difference in the timescale over which each indicator traces star formation, or
exceptionally hot IR-emitting dust in these ultra-dense galaxies.
