We have observed a molecular clump (MM3) associated with the infrared dark cloud G34.43+00.24 in the CH3OH J_K=9_{ -1}--8_0 E, 5_0-4_0 E, and 5_{ -1}-4_{ -1} E lines at sub-arcsecond resolution by using the Atacama Large Millimeter/submillimeter Array. By comparing the CH3OH J_K=9_{ -1}-8_0 E emission with the CH3OH 5_0-4_0 E and 5_{ -1}-4_{ -1} E emission, we have found that the CH3OH J_K=9_{ -1}-8_0 E emission is masing. We have clearly shown that the CH3OH J_K=9_{ -1}-8_0 masers arise from the post shocked gas in the interacting regions between the outflows and ambient dense gas. Toward the strongest peak of the CH3OH maser emission, SiO J=6-5 emission is very weak. This indicates that the CH3OH maser emission traces relatively old shocks or weak shocks.
Categories: astro-ph.SR