Understanding Giant Radio Galaxy J1420-0545: Large-Scale Morphology,
  Environment, and Energetics
  In this paper we consider the possibility that the structure of the largest
radio galaxy J1420-0545 is formed by a restarted rather than a primary jet
activity. This hypothesis is motivated by the unusual morphological properties
of the source, suggesting almost ballistic propagation of powerful jets in a
particularly low-density environment. New radio observations of J1420-0545
confirm its morphology consisting of only two narrow lobes; no trace of any
outer low-density cavity due to the previous jet activity is therefore
detected. Different model fits performed using the newly accessed radio data
imply relatively young age of the source, its exceptionally high expansion
velocity, large jet kinetic power, and confirm particularly low-density
environment. We find that it is possible to choose a realistic set of the model
parameters for which the hypothetical outer lobes of J1420-0545 are old enough
so that their expected radio surface brightness is substantially below the rms
noise level of the available radio maps. On the other hand, the extremely low
density of the gas surrounding the J1420-0545 lobes is consistent with the mean
density of the baryonic matter in the Universe. This suggests that the source
may be instead located in a real void of the galaxy and matter distribution. In
both cases the giant radio lobes of J1420-0545 are expected to modify
substantially the surrounding matter by driving strong shocks and heating the
gas located at the outskirts of the filamentary galactic distribution. Finally,
we also find that the energetic requirements for the source are severe in terms
of the total jet power and the total energy deposited by the outflows far away
from the central engine.
