Determination of the intrinsic velocity field in the M87 jet
  A new method to estimate the Doppler beaming factor of relativistic
large-scale jet regions is presented. It is based on multiwaveband fitting to
radio-to-X-ray continua with synchrotron spectrum models. Combining our method
with available observational data of proper motions, we derive the intrinsic
velocity as well as the viewing angles to the line of sight for eight knotty
regions down the M87 jet. The results favor the 'modest beaming' scenario along
the jet, with Doppler factors varying between 2-5. The inner jet of M87 suffers
sharp deceleration, and the intrinsic speed remains roughly constant down the
outer jet. The orientation of the inner jet regions is fully consistent with
the result of 10deg-19deg to the line of sight suggested by previous Hubble
Space Telescope (HST) proper motion studies of the M87 jet. The outer jet,
however, shows systematic deflection off the inner jet to much smaller
inclination (<<10deg). Further calculation of knot A suggests this deflection
can be regarded as evidence that the outer jet suffers some departure from
equipartition. The nucleus region of the M87 jet should have a viewing angle
close to its first knot HST-1, i.e. ~15deg, which favors the idea that M87 may
be a misaligned blazar. This work provides some hints about the overall
dynamics of this famous extragalactic jet.
