Silicon monoxide and methanol emission from the NGC 2071 molecular outflow

We report observations of emission in the J = 3 --> 2 and J = 2 --> 1 trans itions of SiO and J(k) = 3(k) --> 2(k) transitions of made with the Swedish -ESO Submillimeter Telescope (SEST), toward the high-velocity, collimated m olecular outflow in NGC 2071. Emission is detected from the lobes, as well as from the central core region, in both species. The spatial distribution of the SiO wing emission, which is detected over a velocity range of simila r to 50 km s(-1), shows three distinct features : a blueshifted clump locat ed toward the northeast, a redshifted clump located toward the southwest, a nd a central structure, with moderate redshifted velocities, located near t he cluster of young stellar objects. The shape of the SiO profiles from the northeast and southwest clumps are distinctly different. The SiO lines fro m the northeast clump exhibit a peak near the velocity of the ambient cloud and a gradual decline toward blueshifted velocities reaching flow velociti es of up to -32 km s(-1). On the other hand, the SiO profiles from the sout hwest clump show a peak emission at a velocity that is redshifted by simila r to8.5 km s(-1) from the ambient gas velocity and a gradual decline in bri ghtness toward the ambient cloud velocity. We suggest that the SiO emission from the clumps are signposts of working surfaces where a collimated jet i s interacting with ambient material, and ascribe the differences in line sh ape to differences in the density of the environment under which the jet is propagating. The abundance of silicon monoxide in the outflow lobes is found to be enhan ced, with respect to that of quiescent ambient gas in dark globules, by at least 2 orders of magnitude (peak enhancement greater than or equal to 500 in the southwest clump and greater than or equal to 170 in the northeast cl ump). The abundance of methanol is considerably more enhanced in the southw est clump (peak enhancement of similar to 500) than in the northwest clump (peak enhancement of similar to 70). We suggest that the large enhancements of methanol and silicon monoxide in the outflow clumps are most likely due to the release from grains of ice mantles and Si-bearing species via shock s produced by the interaction between the outflow and dense ambient gas, an d attribute the differences in enhancements to the different shock velociti es attained in the northeast clump (v(s) similar to 45 km s(-1)) and southw est clump (v(s) similar to 12 km s(-1)).