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 simila r to 1.5-arcsec spatial and 14 km s(-1) velocity resolution, obtained with a scanning Fabry-Perot interferometer, it provides the most exten sive data base pet obtained on both the distribution and the dynamics of the shocked molecular gas in this source. The line profiles are bro ad and generally smooth all over the source, with total extent (FWZI) up to similar to 150 km s(-1). We have identified, however, two distin ct components to the line profiles which have different spatial distri butions. Over the entire source, strong emission from a central veloci ty component is present, close to the ambient cloud velocity, while em ission from high-velocity components (both red and blueshifted) is con fined to discrete condensations. The central velocity component peaks, on average, at v(LSR)similar to + 12 km s(-1), with an average FWHM o f similar to 37 km s(-1), but shows subtle variation across the source . In particular, the strongest emission region, Peak 1 to the north-we st, 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 collim ated by a disc, so that it flows close to the plane of the sky but wit h Peak 1 pointing slightly towards us and interacting with ambient mol ecular gas to excite the molecular hydrogen emission. In addition, hig h-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 discr ete locations, primarily along an emission ridge running north along t he Peak 1 region and towards the circumstellar disc about the IRc2 com plex. We develop an analytical shock model to demonstrate that these d iscrete emission knots closely resemble the emission expected from par tially resolved bow shocks. We ascribe these features to additional 'b ullets' to those identified by Allen & Burton in [Fe II] at greater di stances from the source, but which have been revealed by their interac tion with dense, ambient molecular gas. They likely originate from a t emporally limited event less than or equal to 1000 yr ago. We provide new estimates on the energetics and the momenta of all the bullets, an d speculate on their origin.