Submillimeter emission from the hot molecular jet HH 211

We observed the HH 211 jet in the submillimeter continuum and the CO ( 3 - 2) and SiO ( 8 - 7) transitions with the Submillimeter Array. The continuum source detected at the center of the outflow shows an elongated morphology, perpendicular to the direction of the outflow axis. The high- velocity emission of both molecules shows a knotty and highly collimated structure. The SiO ( 8 - 7) emission at the base of the outflow, close to the driving source, spans a wide range of velocities, from - 20 up to 40 km s (- 1). This suggests that a wide- angle wind may be the driving mechanism of the HH 211 outflow. For distances >= 5 (n) (similar to 1500 AU) from the driving source, emission from both transitions follows a Hubble- law behavior, with SiO ( 8 - 7) reaching higher velocities than CO ( 3 - 2) and being located upstream of the CO ( 3 - 2) knots. This indicates that the SiO ( 8 - 7) emission is likely tracing entrained gas very close to the primary jet, while the CO ( 3 - 2) is tracing less dense entrained gas. From the SiO ( 5 - 4) data of Hirano et al., we find that the SiO ( 8 - 7)/ SiO ( 5 - 4) brightness temperature ratio along the jet decreases for knots far from the driving source. This is consistent with the density decreasing along the jet, from cm (- 3) at 500 AU to cm (- 3) at 5000 AU from the driving source.