A Star-Forming Shock Front in Radio Galaxy 4C+41.17 Resolved with
  Laser-Assisted Adaptive Optics Spectroscopy
  Near-infrared integral-field spectroscopy of redshifted [O III], H-beta and
optical continuum emission from z=3.8 radio galaxy 4C+41.17 is presented,
obtained with the laser-guide-star adaptive optics facility on the Gemini North
telescope. Employing a specialized dithering technique, a spatial resolution of
0.10 arcsec or 0.7 kpc is achieved in each spectral element, with velocity
resolution of ~70 km/s. Spectra similar to local starbursts are found for
bright knots coincident in archival Hubble Space Telescope (HST)
restframe-ultraviolet images, which also allows a key line diagnostic to be
mapped together with new kinematic information. There emerges a clearer picture
of the nebular emission associated with the jet in 8.3 GHz and 15 GHz Very
Large Array maps, closely tied to a Ly-alpha-bright shell-shaped structure seen
with HST. This supports a previous interpretation of that arc tracing a bow
shock, inducing 10^10-11 M_solar star-formation regions that comprise the
clumpy broadband optical/ultraviolet morphology near the core.
