WFPC2 Imaging of HH1-2 and HH34

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Session 48 -- Young Stars
Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm

[48.01] WFPC2 Imaging of HH1-2 and HH34

J.J. Hester, P.A. Scowen (ASU), R. Lynds, E.J. O'Neil, Jr. (KPNO), WF/PC IDT

We present HST WFPC2 images of the outflow sources, jets, and bow shocks in HH1-2 and HH34. In HH34 the outflow source appears as an unresolved point source located at the apex of a small conical reflection nebula. The jet itself changes direction several times along its length, with the first kink coming within about 1\arcsec\ of the source. This might be evidence for precession in the outflow source. The well known knots along the jet do not appear to have the morphology expected of Mach diamonds. Rather, they have the appearance of increasingly better developed bow shocks long the length of the jet, reminiscent of simulations of pulsed jet models (e.g., Norman, 1992, in ``Astrophysical Jets,'' p232). The base of the HH1-2 jet is truncated by a finger of obscuration $\sim 0\farcs5$ wide which is inclined by about 30\deg\ from the normal to the jet. The jet is resolved along its entire length, up to the point that it meets the finger of obscurring material. There are two emission knots located off to the side of the main jet. A line through these two knots is very nearly perpendicular to the finger of obscuration. These two knots appear to lie along the line of a proper motion vector pointing to the WNW of the base of the jet in the proper motion data presented by Ray and Mundt (1992, in ``Astrophysical Jets,'' p155), which would support their interpretation as an outflow. The outer of these knots is much stronger in H$\alpha$ than the jet or the inner knot, suggesting that it may be at least in part due to a shock driven into ambient material. The HH region bow shocks in HH1, HH2, and HH34S are all imaged in H$\alpha$ and [S~II]. HH1-2 are imaged in [O~III], as well. The three bow shocks show a wide range of morphology at HST resolution. Common morphologies include sharp H$\alpha$ filaments tracing the location of the shock, and bounding regions of more diffuse [S II] emission; less sharp interfaces along which the H$\alpha$ is stronger on the inside and [S~II] stronger on the outside, suggestive of a shock propagating into outflow material; and well defined knots with high excitation emission along their outward faces, as expected for ``bullets.''

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