J1110+4817 -- a compact symmetric object candidate revisited
  Compact symmetric objects (CSOs) are radio-emitting active galactic nuclei
(AGNs) typically with a double-lobed radio structure confined to within 1 kpc.
CSOs represent the earliest evolutionary phase of jetted AGNs. Some of them may
eventually evolve into large-scale extended double sources, while others stall
within the host galaxy and die out, depending on the longevity of nuclear
activity, the jet power, and parameters of the surrounding galactic
environment. Studying CSOs is a useful tool for understanding the evolution of
the galaxies and the interactions between the jets and the medium of the host
galaxy. Based on milliarcsec-resolution imaging observations using very long
baseline interferometry (VLBI), it is not always straightforward to distinguish
between a compact double-lobed or a core-jet structure. The quasar J1110+4817
was considered a CSO candidate in the literature earlier, but because of the
lack of clear evidence, it could not be securely classified as a CSO. Here we
present a comprehensive analysis of archival multi-frequency VLBI observations
combined with accurate Gaia optical astrometric information. Lower-frequency
VLBI images reveal an extended radio feature nearly perpendicular to the main
structural axis of the source, apparently emanating from the brighter northern
feature, that is rare among the known CSOs. While the presence of a binary AGN
system cannot be fully excluded, the most plausible explanation is that
J1110+4817 is a CSO.
