An excitation study of bow shocks driven from protostars in S233IR^*

¹ MPI für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
² Armagh Observatory, Armagh BT61 9DG, Northern Ireland, UK e-mail: mds@star.arm.ac.uk
³ Joint Astronomy Centre 660 N. A'Ohoku Place, University Park, Hilo, Hawaii 96720, USA e-mail: c.davis@jach.hawaii.edu
⁴ MPI für Radioastronomie, Auf dem Hügel 69, 53121, Bonn, Germany e-mail: tstanke@mpifr-bonn.mpg.de

Corresponding author: T. Khanzadyan, khtig@mpia-hd.mpg.de

Received: 11 August 2003
Accepted: 19 January 2004

Abstract

We present narrow-band near-infrared images of the high-mass star formation region S233IR. We detect several groups of molecular hydrogen knots aligned with known outflows. Images in vibrationally-excited H₂ and [Fe II] reveal the excitation distributions across the main two conspicuous bow shocks. Emission from the [Fe II] line is strong and located at the apex of both bow shocks as well as other locations within the northern bow where we distinguish a compact Mach disk through its [Fe II] emission. The H₂ emission is not restricted to the bow wings but distinct components are detected near the bow apices. The data are broadly comparable to steady bow shocks of speed 60–80 km s^-1 possessing dissociative caps and C-type flanks. Nevertheless, non-steady bow shock behavior is essential to interpret all aspects of the bow structures. In this respect, the S233 bow caps may be in the neutral transformation stage from J-type to C-type.