1Particle acceleration and jet dynamics in Centaurus A

New multi-epoch Chandra observations, combined with multi-epoch, high-dynamic range VLA data, have allowed us to relate the radio and X-ray structure of the jet in Cen A to the jet dynamics. We present evidence that a significant fraction of the structure in the Cen A X-ray jet is due to particle acceleration at the interaction between the jet flow and internal galactic material. 1. Low-luminosity jets The general properties of jets in FRI radio galaxies are now comparatively well understood. On parsec scales, jets in FRIs are similar to those in the more powerful FRIIs; they are well colli-mated and relativistic. On scales of a few kpc, however, the FRI jets disrupt as they come into pressure balance with the external medium, be-coming much less well collimated and less efficient as energy transport mechanisms, and producing the characteristic bright, broad jet emission seen on arcsecond scales with instruments such as the VLA. The jets decelerate from relativistic to sub-relativistic speeds on scales of a few kpc, showing significant transverse velocity structure [1]. The deceleration is likely to be a result of entrainment of external material, and the jet is stabilized by the strong pressure gradient in the centre of the host galaxy [1–3]. It is now possible to make detailed quantitative models of these jets, which agree well with observation (e.g. [3]). 2. Beyond the standard picture These jet models do not tell us why the jets are observed: how do the jet dynamics give rise to the population of high-energy particles responsi-ble for the observed synchrotron emission? The energy required for particle acceleration must cer-tainly come from the bulk kinetic energy of the jet, but the mechanism the jets use to tap this energy is not clear. In recent years X-ray observations of jets hav