EDP Sciences
Free access
Volume 412, Number 3, December IV 2003
Page(s) 727 - 734
Section Stellar clusters and associations
DOI http://dx.doi.org/10.1051/0004-6361:20031276

A&A 412, 727-734 (2003)
DOI: 10.1051/0004-6361:20031276

H $\mathsf{_2}$ excitation imaging of the Orion Molecular Cloud

L. E. Kristensen1, M. Gustafsson1, D. Field1, G. Callejo2, 3, J. L. Lemaire2, 3, L. Vannier2 and G. Pineau des Forêts4

1  Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C, Denmark
2  Observatoire de Paris-Meudon, LERMA and UMR 8112 of the CNRS, 92195 Meudon Principal Cedex, France
3  Université de Cergy-Pontoise, LERMA and UMR 8112 of the CNRS, 95806 Cergy Cedex, France
4  Institut d'Astrophysique Spatiale, Université Paris XI, 91405 Orsay Cedex, France

(Received 30 January 2003 / Accepted 11 August 2003)

Observations are reported of IR emission in H 2, around 2  $\mu$m in the K-band, obtained with the ESO 3.6 m telescope using the ADONIS adaptive optics system. Data cover a region of the Orion Molecular Cloud north of the Trapezium stars and SW of the Becklin-Neugebauer object. Excellent seeing yielded diffraction limited images in the v=2-1 S(1) line at 2.247  $\mu$m. Excitation temperature images were created by combining these data with similar data for H 2 emission in the v=1-0 S(1) line reported earlier (Vannier et al. 2001). Shock models are used to estimate densities in emitting clumps of material. In local zones with high excitation temperatures, post-shock densities are found to be as high as several times 10 8 cm -3, an order of magnitude denser than our previous estimates. We propose that the nature of these zones is dictated by the combined activity of shocks, which create dense structures, and the powerful radiation field of $\theta$ 1C Ori which photoevaporates the boundaries of these structures.

Key words: ISM: individual objects: OMC1 -- ISM: kinematics and dynamics -- ISM: molecules -- shock waves -- ISM: lines and bands

Offprint request: D. Field, dfield@phys.au.dk

SIMBAD Objects

© ESO 2003