2007ApJ...671..536C

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. Line strengths for the H₂1-0 S(4) plus 2-1 S(6) lines at 1.89 µm are estimated from measurements with the Paschen-α continuum filter F190N at 1.90 µm and continuum measurements at 1.66 and 2.15 µm. We compare the observed H₂ line strengths and ratios of the 1.89 and 2.12 µm 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 10⁴-10⁶/cm3, similar 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.