Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994ap%26ss.216..135e&link_type=abstract
Astrophysics and Space Science, vol. 216, no. 1-2, p. 135-136
Astronomy and Astrophysics
Astrophysics
2
Gas Dynamics, Herbig-Haro Objects, Interstellar Gas, Magnetohydrodynamic Flow, Molecular Flow, Molecular Gases, Plasma Jets, Stellar Models, Stellar Winds, Bipolarity, Entrainment, Flow Velocity, Shock Waves
Scientific paper
Herbig-Haro (HH) 46/47 is a well studied bipolar jet system emanating from an isolated Bok globule in the Gum Nebula. It consists of the bright, blue-shifted HH 46/47 jet, which shows a wealth of internal structure (see, e.g., Reipurth & Heathcote 1991) and ends in the bright knot HH47A, which is thought to be its bow shock (e.g., Meaburn & Dyson 1987). However, a second, fainter, but much more extended bow shock HH47D is found ahead of HH47A. On the opposite side of the jet source, seen only in the infrared (IR) (Graham & Elias 1983), a faint counter jet points towards the redshifted bow shock HH47C (Meaburn & Dyson 1987). A detailed study has be carried out of the proper motions of the knots in the HH 46/47 jet and counterjet, as well as of the condensations in the associated bow shocks HH47C and HH47D. In the jet most tangential velocities are in the range 100-300 km/s (see Fig. 1), while in the other parts of the system the measured values are mainly somewhat lower at 70-170 km/s. Given reasonable assumptions about the pattern speed at the apex of the presumed bow shock HH47A the orientation of the HH 46/47 outflow is determined to be 34.1 deg +/- 2.8 deg (Eisloeffel 1992, Eisloeffel & Mundt 1993). This allows us to correct the observed radial and tangential velocities in the jet for projection effects, enabling the local flow speed of the jet and the know pattern speed to be derived. A typical flow speed of about 290 km/s is found in the jet. The ratio zeta between the pattern speed of the knots and the flow speed of the particles in the jet displays a bimodal distribution with the two values zeta = 0.62 +/- 0.05 and zeta = 0.95 +/- 0.06. This bimodal distribution, if real, is difficult to understand with current jet models. Ambient material may be entrained into the jet along parts of the jet channel and seen as a separate flow component.
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