SiO in G34.26: Outflows and shocks in a high mass star forming region

Abstract

We have looked for SiO emission as evidence of shocks in the high mass star formation region G34.26+0.15. JMCT, VLA and FCRAO observations show that SiO emission is widespread across the region. The SiO emission highlights a massive, collimated outflow and other regions where stellar winds are interacting with molecular clumps. As in other star forming regions, there is also SiO at ambient velocities which is related to the outflow activity. No strong SiO abundance enhancement was measured in either the outflow or the low velocity gas, though abundances up to 10-8 are possible if the SiO is locally enhanced in clumps and optically thick. SiO emission is not detected from the hot core itself, indicating either SiO is not strongly enhanced in the hot core or that column densities in the region where grain mantle evaporation has taken place are low. In line of sight spiral arm clouds, we measure a SiO abundance of 0.4-2 × 10-10, consistent with previous estimates for quiescent clouds.