J2102+6015: a young radio source at z = 4.575
  Jets of high-redshift active galactic nuclei (AGNs) can be used to directly
probe the activity of the black holes in the early Universe. Radio sources with
jets misaligned with respect to the line of sight are expected to dominate the
high-redshift AGN population. In this paper, we present the high-resolution
imaging results of a z=4.57 AGN J2102+6015 by analyzing its multi-epoch
dual-frequency very long baseline interferometry (VLBI) data. The 8.4-GHz VLBI
images reveal two major features along the east-west direction separated by
$\sim$ 10 milli-arcsec (mas). From the spectral index map, both features show
flat/inverted spectra. The separation between the two features remains almost
unchanged over an observation period of $\sim$ 13 years, placing an upper limit
of the separation speed as about 0.04 mas year$^{-1}$. Previous studies have
classified the source as a GHz-peaked spectrum quasar. Our results indicate
that J2102+6015 is most likely a young, compact symmetric object rather than a
blazar-type core-jet source.
