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HH 666 is an externally irradiated protostellar outflow in the Carina Nebulafor which we present new near-IR [Fe II] spectra obtained with the FIREspectrograph at Magellan Observatory. Earlier H{\alpha} and near-IR [Fe II]imaging revealed that the two emission lines trace substantially differentmorphologies in the inner ~40" of the outflow. H{\alpha} traces a broad cocoonthat surrounds the collimated [Fe II] jet that extends throughout the parentdust pillar. New spectra show that this discrepancy extends to theirkinematics. Near-IR [Fe II] emission traces steady, fast velocities of +/- 200km/s from the eastern and western limbs of the jet. We compare this to apreviously published H{\alpha} spectrum that reveals a Hubble-flow velocitystructure near the jet-driving source. New, second-epoch HST/ACS H{\alpha}images reveal the lateral spreading of the H{\alpha} outflow lobe away from thejet axis. H{\alpha} proper motions also indicate a sudden increase in themass-loss rate ~1000 yr ago, while steady [Fe II] emission throughout the innerjet suggests that the burst is ongoing. An accretion burst sustained for ~1000yr is an order of magnitude longer than expected for FU Orionis outbursts, butrepresents only a small fraction of the total age of the HH 666 outflow.Altogether, available data suggests that [Fe II] traces the highly collimatedprotostellar jet while H{\alpha} traces the entrained and irradiated outflow.HH 666 appears to be a missing link between bare jets seen in H II regions andentrained molecular outflows seen from embedded protostars in more quiescentregions.

HH 666: Different kinematics from H{\alpha} and [Fe II] emission provide a missing link between jets and outflows