Interpretation of the Radio/X‐Ray Knots of AGN Jets within the Internal Shock Model Framework

The dynamics of relativistically moving blobs ejected out of a central AGN,are considered. It is assumed that the collision between two blobs arecompletely inelastic, such that the bulk kinetic energy lost in the collisionis used to energize electrons to relativistic energies via acceleration ininternal shocks which are formed due to the collision. These high energyelectrons which are produced on a time-scale corresponding to the collisiontime-scale, cool by radiative losses due to synchrotron and Inverse Comptonprocesses. The model is applied to the radio/X-ray knots of several AGN. Forthree of these sources we have analyzed long (> 40 ksec) Chandra observationsand report on constrains on the X-ray spectral indices. In the framework ofthis model the AGN are inferred to sporadically eject relativistic blobs ontime-scales ranging from 10^{11} to 10^{12} secs for different sources. It isshown that the collision time-scales can be longer than the age of the knotand, hence, non-thermal electrons are continuously being injected into thesystem. This continuous injection, in contrast to an instantaneous one timeinjection, gives rise to a characteristic spectral break, rather than ahigh-energy cutoff in the spectrum.Comment: Accepted for publication in Astrophysical Journa