Dr Teddy Cheung (NRAO and MIT)

Panchromatic Views of Large-Scale Quasar Jets - Dr Teddy Cheung Colloquium

ATNF Marsfield Lecture Theatre

Abstract

Chandra observations have established that X-ray emission is a common
feature of large-scale jets in AGN. In nearby low-power radio sources,
there is wide agreement that the X-ray emission originates via the
synchrotron process. This requires relativistic electrons with Lorentz
factors of order 10 million in the X-ray emitting sites (the first few
kilo-parsecs of the jet). In the X-ray jets detected on 100's kpc-scales
in powerful quasars, canonical synchrotron models do not adequately fit
the multi-wavelength spectra. In these cases, a widely applied model is
inverse Compton (IC) scattering off CMB photons by relativistic electrons
in the jet emitting low frequency radio emission. However, this model
requires much larger bulk jet speeds on 100's kpc-scales than inferred
from, e.g. radio jet asymmetry studies. The quasar jet observations still
pose challenges for the inverse Compton and "non-standard" synchrotron
models, and no concensus has been reached.

I will give an overview of this subject, highlighting results from recent
observations. Then, a number of important implications of the highly
relativistic kpc-scale quasar jets (as required in the IC/CMB model) are
outlined. In particular, the infrared to gamma-ray emission from these
jets become important. Particular attention is paid to the spatial
distribution of the possible IC emission considering also other sources of
seed photons. Finally, the IC/CMB model makes some straightforward
predictions about the redshift and beaming dependence of the X-ray
emission and tests are proposed. Recent results from studies of the
highest-redshift radio/X-ray quasar jets will be discussed.