Testing the beamed inverse‐Compton model for jet X‐ray emission: velocity structure and deceleration

By considering a small sample of core‐dominated radio‐loud quasars with X‐ray jets, I show, as has been argued previously by others, that the observations require bulk jet deceleration if all of the X‐ray emission is to be explained using the widely adopted beamed inverse‐Compton model, and argue that jets even in these powerful objects must have velocity structure in order to reconcile their radio and X‐ray properties. I then argue that the deceleration model has several serious weaknesses, and discuss the viability of alternative models for the decline in X‐ray/radio ratio as a function of position. Although inverse‐Compton scattering from the jets is a required process and must come to dominate at high redshifts, adopting an alternative model for the X‐ray emission of some nearby, well‐studied objects can greatly alleviate some of the problems posed by these observations for the beamed inverse‐Compton model.