High-resolution VLA Imaging of Obscured Quasars: Young Radio Jets Caught
  in a Dense ISM
  We present new sub-arcsecond-resolution Karl G. Jansky Very Large Array (VLA)
imaging at 10 GHz of 155 ultra-luminous ($L_{\rm bol}\sim10^{11.7-14.2}
L_\odot$) and heavily obscured quasars with redshifts $z \sim0.4-3$. The sample
was selected to have extremely red mid-infrared (MIR)-optical color ratios
based on data from Wide-Field Infrared Survey Explorer (WISE) along with a
detection of bright, unresolved radio emission from the NRAO VLA Sky Survey
(NVSS) or Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) Survey.
Our high-resolution VLA observations have revealed that the majority of the
sources in our sample (93 out of 155) are compact on angular scales
$<0.2^{\prime \prime}$ ($\leq 1.7$ kpc at $z \sim2$). The radio luminosities,
linear extents, and lobe pressures of our sources are similar to young radio
active galactic nuclei (AGN; e.g., Gigahertz Peaked Spectrum, GPS, and Compact
Steep Spectrum, CSS, sources), but their space density is considerably lower.
Application of a simple adiabatic lobe expansion model suggests relatively
young dynamical ages ($\sim10^{4-7}$ years), relatively high ambient ISM
densities ($\sim1-10^4$ cm$^{-3}$), and modest lobe expansion speeds
($\sim30-10,000$ km s$^{-1}$). Thus, we find our sources to be consistent with
a population of newly triggered, young jets caught in a unique evolutionary
stage in which they still reside within the dense gas reservoirs of their
hosts. Based on their radio luminosity function and dynamical ages, we estimate
only $\sim20\%$ of classical large scale FRI/II radio galaxies could have
evolved directly from these objects. We speculate that the WISE-NVSS sources
might first become GPS or CSS sources, of which some might ultimately evolve
into larger radio galaxies.
