Jl. Gomez et al., PARSEC-SCALE SYNCHROTRON EMISSION FROM HYDRODYNAMIC RELATIVISTIC JETSIN ACTIVE GALACTIC NUCLEI, The Astrophysical journal, 449(1), 1995, pp. 19-21
We present the first numerical simulations of the parsec-scale synchro
tron emission from hydrodynamic relativistic jets. The jet structure i
s calculated using a relativistic time-dependent hydrodynamic code bas
ed on an approximate Riemann solver. The radio emission from the model
jets is calculated by integrating the transfer equations of the synch
rotron radiation, accounting for the appropriate opacity and relativis
tic effects, such as Doppler boosting and relativistic aberration. In
order to study the influence of the external medium, we present two hy
drodynamical jet simulations: one with a constant external pressure, a
nd a second model with a decreasing external pressure. Multifrequency
radio images of the synchrotron emission from these flows are presente
d, showing the existence of stationary quasi-periodic knots associated
with internal oblique shocks. Whereas for the model with constant ext
ernal pressure the knots remain almost constant in intensity and even
in spacing, the model with decreasing external pressure shows stationa
ry knots of progressively lower intensity and wider spacing as a funct
ion of distance down the jet.