NICMOS Observations of Shocked H 2 in Orion - AstrophysicsReport as inadecuate

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Abstract: HST NICMOS narrowband images of the shocked molecular hydrogen emission inOMC-1 are analyzed to reveal new information on the BN-KL outflow. Theoutstanding morphological feature of this region is the array of molecularhydrogen ``fingers- emanating from the general vicinity of IRc2 and thepresence of several Herbig-Haro objects. The NICMOS images appear to resolveindividual shock fronts. This work is a more quantitative and detailed analysisof our data from a previous paper Schultz etal. 1999.Line strengths for the H 2 1-0 S4 plus 2-1 S6 lines at 1.89 micron areestimated from measurements with the Paschen alpha continuum filter F190N at1.90 micron, and continuum measurements at 1.66 and 2.15 micron. We compare theobserved H 2 line strengths and ratios of the 1.89 micron and 2.12 micron 1-0S1 lines with models for molecular cloud shock waves. Most of the data cannotbe fit by J-shocks, but are well matched by C-shocks with shock velocities inthe 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 manyshocks. There is also some evidence that shocks with higher densities havelower velocities.

Author: Sean W.J. Colgan, A.S.B. Schultz, M.J. Kaufman, E.F. Erickson, D.J. Hollenbach


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