Methanol and silicon monoxide observations toward bipolar outflows associated with Class 0 objects

Abstract

We report Swedish-ESO Submillimetre Telescope observations of seven bipolar outÑows thought to be associated with Class 0 objects in the t\0 J\3]2 and J\2]1 transitions of SiO and Jk\ 3k and transitions of Methanol and silicon monoxide emission from out- ]2k Jk\2k ]1k CH3OH. Ñowing gas were detected toward the lobes of four objects (NGC 2264G, IRAS 16293[2422, Serpens S68N, and Serpens SMM 4). The SiO line proÐles are characteristics of C-type bow shocks, showing a peak at a radial velocity close to but displaced from the ambient cloud velocity and a gradual decrease in intensity from the peak toward higher Ñow velocities. There is a signiÐcant correlation between the column density of SiO and the terminal SiO Ñow velocity, which suggests a velocity-selective enhancement in the production of SiO molecules. We Ðnd that the SiO abundance in the lobes is enhanced with respect to that of the ambient cloud by a factor of at least 330 in IRAS 16293[2422 and SMM 4, 170 in NGC 2264G, and 80 in S68N. The CH abundance is enhanced by a factor of 500 in 3OH IRAS 16293[2422, 330 in SMM 4, 80 in S68N, and 23 in NGC 2264G. In addition, we Ðnd that the dependence of the SiO/CO and CH abundance ratios with radial Ñow velocity shows a steep 3OH/CO increase in the range from D0 to D4È5 km s~1 and a gradual decline toward higher Ñow velocities. In the remaining three sources (CG 30, IRAS 13036[7644, and VLA 1623[243), emission in methanol was detected from a narrow line at the velocity of the ambient cloud, and no emission was detected in silicon monoxide. Weak methanol emission from a low-velocity outÑow component was detected toward CG 30.