The kinematics of HH34 from HST images with a nine-year time baseline

Abstract

We study archival HST [S II] 6716+30 and Hα images of the HH34 outflow, taken in 1998.71 and in 2007.83. The 9yr time baseline and the high angular resolution of these observations allow us to carry out a detailed proper-motion study. We determine the proper motions of the substructure of the HH34S bow shock (from the [S II] and Hα frames) and of the aligned knots within 30″ from the outflow source (only from the [S II] frames). We find that the present-day motions of the knots along the HH34 jet are approximately ballistic, and that these motions directly imply the formation of a major mass concentration in 900yr, at a position similar to the one of the present-day HH34S bow shock. In other words, we find that the knots along the HH34 jet will merge to form a more massive structure, possibly resembling HH34S. © 2012. The American Astronomical Society. All rights reserved.