THE PUZZLING DISTRIBUTION OF THE HIGH-DENSITY MOLECULAR GAS IN HH-1-2- A CONTRACTING INTERSTELLAR TOROID

We have performed a mosaic analysis of the region containing the HH 1- 2 system. We combined five fields of NH3(1, 1) and (2, 2) spectral lin e observations using the VLA in its D configuration. This mosaic analy sis allowed us to recover similar to 80% of the total NH3(1, 1) flux o btained with single-dish observations. The total mass of the molecular gas in the region is estimated to be similar to 52 (X(NH3)/10(-8))(-1 ) M.. We find two remarkable elongated structures of similar to 0.4 pc (similar to 3') in size, approximately parallel to each other, while oriented almost perpendicular to the HH 1-2 outflow and the magnetic f ield in the region. The major axes of these elongated structures are d isplaced similar to 20'' northwest and similar to 10'' southeast of VL A 1, respectively. There is a velocity difference of similar to 2 km s (-1) between the two structures, but there is no significant velocity gradient along the major axis of either structure. Molecular gas at in termediate velocities between the velocities of the two elongated stru ctures is found at their northeastern and southwestern ends. The excit ing source of the HH 1-2 outflow may be physically closer to the elong ated molecular structure displaced to the southeast of VLA 1, since th e gas temperature is higher there, T-K similar or equal to 18 K. The k inematical and spatial distribution of the elongated structures with r espect to the [S II] emission of the HH 1-2 system, the blueshifted mo tions of HH 1 with respect to HH 2, the ambient velocities observed at the ends of the elongated structures, and finally the velocity gradie nt observed along the minor axis of the southeastern elongated structu re, are consistent with a scenario where these two elongated structure s represent the two halves of a contracting self-gravitating interstel lar toroid seen almost edge-on, with the southeastern side in the fore ground and redshifted with respect to the northwestern side. We favor a scenario where the star formation processes in the HH 1-2 region hav e produced at least two concentric flattened structures surrounding VL A 1, one with an interstellar size of similar to 0.4 pc and the other one two orders of magnitude smaller (less than or similar to 10(3) AU) . This smaller structure, not evident in our data, is required to coll imate the jet from VLA 1. Within this scenario, the HH 1-2 system woul d represent a case where the idea that inflow and outflow are taking p lace simultaneously in young stellar objects is supported.