Proper Motions of the HH 47 Jet Observed with the Hubble Space Telescope
Hartigan, P. (Rice), Heathcote, S. (CTIO), Morse, J. (ASU), Reipurth, B. (Hawaii), and Bally, J. (Colorado)
We present a proper motion study of the shock waves
within the classic stellar jet HH 47 based on Hubble Space Telescope
H-alpha and [S II] images of the region taken over two epochs.
Individual knots within the jet and in the bow shock/Mach disk working surface of HH 47A
move significantly in the five years that separate the images, and the
excellent spatial resolution of HST makes it possible
to measure the proper motions with enough precision to easily observe
differential motions throughout the flow. The bright portion of the jet emerges at
37.5 +/- 2.5 degrees from the plane of the sky with an average velocity of 300 km/s.
Dynamical ages of the shock waves in the jet range from a few decades for knots
recently ejected by the source to ~ 1300 years for the faint extended bow
shock HH 47D. The jet curves, but motions of knots in the jet are directed
radially away from the exciting source, and velocity variability in the
flow drives the shock waves that heat the jet internally.
The jet orientation angle varies with time by about 15 degrees,
and currently points to the northwestern
portion of a cavity outlined by a reflection nebula, where a quasi-stationary
shock deflects the jet. The major working surface HH 47A is more complex than a
simple bow shock/Mach disk, and contains numerous clumps that move relative
to one another with velocities of ~ +/- 40 km/s. Small clumps
or instabilities affect the Mach disk, and dense clumps may move all the
way through the working surface to cause the bumpy morphology seen at the bow shock.
A localized area between the bow shock and Mach disk
varies significantly between the two sets of images.
2005, AJ 130, 2197