A Fresh Look at Narrow-Angle Tail Radio Galaxy Dynamics, Evolution and
  Emissions
  We present a 3D magnetohydrodynamic (MHD) study of narrow-angle tail (NAT)
radio galaxy (RG) dynamics, including passive cosmic ray electrons. We follow
evolution of a bipolar-jet RG in a persistent crosswind through hundreds of
Myr. We confirm traditional jet-bending models, while noting that our NAT
exhibits a transitional morphology reminiscent of wide-angle radio tails. Once
deflected, jets remain internally stable, but are intermittently disrupted by
external disturbances induced by the NAT dynamics itself. The disruptions
enhance jet and tail magnetic fields. Disrupted jet plasma is heterogeneously
mixed with denser wind plasma, yielding patchy, filamentary tails that grow
longer at a rate exceeding the wind speed. Such fast tail extension could, for
example, allow NAT tails to overtake extraneous ICM features, such as shocks
and shear layers downwind of where the tails first form. Those events, in turn,
could generate enhanced radio emissions within the ICM features themselves that
do not follow the geometrical extension of the tails past the encounter.
Analysis of synthetic radio observations reveals an extended time period once
the NAT has developed in which it displays a nearly steady-state morphology
with integrated fluxes that are roughly constant, along with a self-similar,
curved integrated spectrum. In an appendix, we outline a simple analytic jet
trajectory formalism with one adjustable parameter, using it to illustrate
explicit trajectories that extend the classic bending model to arbitrary
jet-wind orientations.
