What gamma-rays tell us about jets

Abstract

The combined synchrotron and inverse Compton emission from jets provide us with essential information on the properties of jets within 100-1000 gravitational radii from the black hole. In some jets the inferred magnetic field is below equipartition and in MKN 501 and MKN 421, recent models imply Doppler factors of approximately 50. Both of these features confront jet-launching models with substantial challenges. In MKN 421 and MKN 501 the jets must decelerate before they reach the parsec scale and this is in fact physically consistent with conservation of energy and momentum in this region. The correlation between the peak Lorentz factor and the inverse of the magnetic plus photon energy density is most directly explained if the shocks in blazar jets are produced by intrinsic jet instabilities rather than variations in the output of the black hole. Recent analysis of a restarting radio jet galaxy provide additional evidence for hyper-relativistic jets.