Volume 366, Number 2, February I 2001
|Page(s)||651 - 661|
|Published online||15 February 2001|
H2 infrared emission and the formation of dense structures in the Orion molecular cloud
Observatoire de Paris-Meudon, 92195 Meudon Principal Cedex, France
2 Université de Cergy-Pontoise UMR 8588 du CNRS, 95806 Cergy Cedex, France
3 Institute of Physics and Astronomy, University of Aarhus, 8000 Aarhus C, Denmark and Observatoire de Paris-Meudon, UMR 8588 du CNRS, France
4 Theoretical Astrophysics Centre, University of Aarhus, 8000 Aarhus C, Denmark
Corresponding author: D. Field, firstname.lastname@example.org
Accepted: 9 November 2000
Observations are reported of IR emission of H2 from a region of the Orion molecular cloud (OMC1) between the Becklin-Neugebauer object and IRc2 to the north and the Trapezium stars to the south. Data were obtained using the ESO 3.6 m telescope in the K-band around 2 μm with the ADONIS adaptive optics system. Images of (1) show a spatial resolution of ∼0.15''. Detailed investigations of the distribution of sizes of structures in our images have been performed by area-perimeter analysis, Fourier analysis and brightness distribution studies. These demonstrate that structure is not fractal but shows a preferred scales of between 3 10-3 and 4 10-3 pc. In an attempt to estimate the density in observed structures, predictions of both shock models and photodissociation region models have been compared with measured emission brightness in the (1) line. Magnetic (C-type) shocks with velocities of 30 km s-1 and pre-shock densities of 106 cm-3 yield the best representation of our data, notwithstanding significant discrepancies for the brightness ratio between (1) and (1) lines. Our results show that post-shock densities are several times 107 cm-3. This is sufficiently high that the passage of C-type shocks in Orion yields gravitational instability which may in turn trigger star formation in the post-shock gas.
Key words: ISM: individual objects: OMC1 / ISM: kinematics and dynamics / ISM: molecules / shock waves / infrared: ISM: lines and bands
© ESO, 2001
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.