Velocity-resolved Fabry-Perot imaging of molecular hydrogen emission in OMC-1

We present a velocity-resolved data cube of the distribution of the v=1-0 S(1) line of molecular hydrogen from the source OMC-1. With similar to 1.5-arcsec spatial and 14 km s(-1) velocity resolution, obtained with a scanning Fabry-Perot interferometer, it provides the most extensive data base pet obtained on both the distribution and the dynamics of the shocked molecular gas in this source. The line profiles are broad and generally smooth all over the source, with total extent (FWZI) up to similar to 150 km s(-1). We have identified, however, two distinct components to the line profiles which have different spatial distributions. Over the entire source, strong emission from a central velocity component is present, close to the ambient cloud velocity, while emission from high-velocity components (both red and blueshifted) is confined to discrete condensations. The central velocity component peaks, on average, at v(LSR)similar to + 12 km s(-1), with an average FWHM of similar to 37 km s(-1), but shows subtle variation across the source. In particular, the strongest emission region, Peak 1 to the north-west, is both slightly blueshifted and broader than the secondary Peak 2 to the south-east of OMC-1. We interpret this emission as the result of an isotropic steady wind from the IRc2 complex being loosely collimated by a disc, so that it flows close to the plane of the sky but with Peak 1 pointing slightly towards us and interacting with ambient molecular gas to excite the molecular hydrogen emission. In addition, high-velocity emission components (centred at similar to -35 km s(-1) and + 40 km s(-1) with FWHM of similar to 30 km s(-1)) are found in discrete locations, primarily along an emission ridge running north along the Peak 1 region and towards the circumstellar disc about the IRc2 complex. We develop an analytical shock model to demonstrate that these discrete emission knots closely resemble the emission expected from partially resolved bow shocks. We ascribe these features to additional 'bullets' to those identified by Allen & Burton in [Fe II] at greater distances from the source, but which have been revealed by their interaction with dense, ambient molecular gas. They likely originate from a temporally limited event less than or equal to 1000 yr ago. We provide new estimates on the energetics and the momenta of all the bullets, and speculate on their origin.