NICMOS Observations of Shocked H_2 in Orion

Abstract

HST NICMOS narrowband images of the shocked molecular hydrogen emission in OMC-1 are analyzed to reveal new information on the BN/KL outflow. The outstanding morphological feature of this region is the array of molecular hydrogen ``fingers'' emanating from the general vicinity of IRc2 and the presence of several Herbig-Haro objects. The NICMOS images appear to resolve individual shock fronts. This work is a more quantitative and detailed analysis of our data from a previous paper (Schultz etal. 1999). Line strengths for the H_2 1--0 S(4) plus 2--1 S(6) lines at 1.89 micron are estimated from measurements with the Paschen_alpha continuum filter F190N at 1.90 micron, and continuum measurements at 1.66 and 2.15 micron. We compare the observed H_2 line strengths and ratios of the 1.89 micron and 2.12 micron 1--0 S(1) lines with models for molecular cloud shock waves. Most of the data cannot be fit by J-shocks, but are well matched by C-shocks with shock velocities in the range of 20--45 km/s and preshock densities of 10^{4} - 10^{6} cm^{-3}, similiar to values obtained in larger beam studies which averaged over many shocks. There is also some evidence that shocks with higher densities have lower velocities.

arXiv comment33 pages, 11 figures, 2 of those color

References in corpus (9)

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• OMC-1 dust polarisation in ALMA Band 7: Diagnosing grain alignment mechanisms in the vicinity of Orion Source I
• The Nature and Frequency of Outflows from Stars in the Central Orion Nebula Cluster
• An HST Imaging Survey of Low-Mass Stars in the Chamaeleon I Star Forming region
• The Explosion in Orion-KL as Seen by Mosaicking the Magnetic Field with ALMA
• Deep diving off the `Cosmic Cliffs': previously hidden outflows in NGC 3324 revealed by JWST
• The Orion fingers: Near-IR spectral imaging of an explosive outflow
• Observational evidence for rotational desorption of Complex Molecules by radiative torques from Orion BN/KL
• Near-infrared and Millimeter-wavelength Observations of Mol 160: A Massive Young Protostellar Core
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