A compact symmetric radio source born at one-tenth the current age of
  the Universe
  Studies of high redshift radio galaxies can shed light on the activity of
active galactic nuclei (AGN) in massive elliptical galaxies, and on the
assembly and evolution of galaxy clusters in the Universe. J1606+3124 has been
tentatively identified as a radio galaxy at a redshift of 4.56, at an era of
one-tenth of the current age of the Universe. Very long baseline interferometry
(VLBI) images show a compact triple structure with a size of 68 parsecs. The
radio properties of J1606+3124, including the edge-brightening morphology,
peaked GHz radio spectrum, slow variability, and low jet speed, consistently
indicate that it is a compact symmetric object (CSO). The radio source size and
expansion rate of the hotspots suggest that J1606+3124 is a young (kinematic
age of ~3600 years) radio source. Infrared observations reveal a gas- and
dust-rich host galaxy environment, which may hinder the growth of the jet;
however, the ultra-high jet power of J1606+3124 gives it an excellent chance to
grow into a large-scale double-lobe radio galaxy. If its redshift and galaxy
classification can be confirmed by further optical spectroscopic observations,
J1606+3124 will be the highest redshift CSO galaxy known to date.
