We present new high-resolution and high-sensitivity studies of the jets in the WAT source 3C 465 , using deep transverse-resolved radio observations from e-MERLIN , and with complementary observations from the VLA .
We derive a lower limit \beta _ { j } = ( \nu _ { j } / c ) \gtrsim 0.5 for the jet speed , and an upper limit \theta _ { j } \lesssim 61 ^ { \circ } for the jet angle to the line of sight .
The jet spectral index ( \alpha , defined in the sense S \propto \nu ^ { \alpha } ) is fairly constant ( < \alpha _ { jet } > = - 0.7 ) , and spectral flattening within 4.4 kpc of the core coincides with bright knots and is consistent with the site of X-ray particle acceleration at the base of the radio jet found in previous studies .
There is little difference between the spectra of the two hotspot components , plausibly indicating that electron populations of the same properties are injected there .
The NW and SE plumes are approximately homologous structures , with variations in mass injection and propagation in external pressure and density gradients in the two regions plausibly accounting for the slightly steeper spectrum in the NW plume , < \alpha _ { NWp } > = - 1.43 compared with the SE plume , < \alpha _ { SEp } > = - 1.38 .
Our synchrotron lifetime model supports plausible reacceleration of particles within the plume materials .
Overall , our results show that the first-order Fermi process at mildly relativistic and non-relativistic shocks is the most likely acceleration mechanism at play in 3C 465 and distinguish differences between the acceleration at \beta _ { j } > 0.5 and \beta _ { j } < 0.5 .
The former case can accelerate electrons to higher Lorentz factors .