Issue |
A&A
Volume 419, Number 3, June I 2004
|
|
---|---|---|
Page(s) | 975 - 990 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20034551 | |
Published online | 07 May 2004 |
A near-infrared study of the bow shocks within the L1634 protostellar outflow
1
Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland, UK
2
Physics Department, Trinity College Dublin, College Green, Dublin 2, Ireland
3
Joint Astronomy Centre, 660 N. A'ohoku Place, University Park, Hilo, Hawaii 96720, USA
4
Institute for Astronomy, University of Hawaii, 640 N. A'ohoku Place, University Park, Hilo, Hawaii 96720, USA
5
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
6
School of Cosmic Physics, Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland
Corresponding author: B. O'Connell, boc@arm.ac.uk
Received:
21
October
2003
Accepted:
25
February
2004
The L1634 bright-rimmed globule contains an intriguing arrangement of
shock structures: two series of aligned molecular
shock waves associated with the Herbig-Haro flows HH 240 and HH 241.
We present near-infrared spectroscopy
and narrow-band imaging in the (1, 0) S(1) and (2, 1) S(1) emission lines of molecular hydrogen.
These observations yield the spatial distributions of both the molecular excitation
and velocity, which demonstrate distinct properties for the individual bow shocks.
Bow shock models are applied, varying the shock physics, geometry, speed, density
and magnetic field properties to fit two prominent bow shocks. The models
predict that both bows move at 60°
to the plane of the sky. High magnetic fields and low
molecular fractions are implied.
The advancing compact bow HH 240C is interpreted as a J-type bow (frozen-in
magnetic field) with the flanks in transition to C-type (field diffusion).
It is a paraboloidal bow of speed ~42 km s-1
entering a medium of quite high density (2 104 cm-3).
The following bow HH 240A is faster despite a lower excitation, moving
through a lower density medium. We find a C-type bow shock model to fit all the
data for HH 240A. The favoured bow models are then tested comprehensively against published
H2 emission line fluxes and CO spectroscopy. We conclude that, while the CO emission
originates from cloud gas directly set in motion,
the H2 emission is generated from shocks sweeping through an outflow. Also
considering optical data, we arrive
at a global outflow model involving episodic slow-precessing twin jets.
Key words: ISM: jets and outflows / stars: circumstellar matter / infrared: stars / ISM: Herbig-Haro objects
© ESO, 2004
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