2006PASJ...58..563T

We present SiO J = 8-7 (347.3GHz) observations towards HH 212 (Herbig-Haro object 212) using the ASTE (Atacama Submillimeter Telescope Experiment) telescope. Our observations with a 22''-diameter beam show that the SiO emission is highly concentrated within 1' of the driving source. We carefully compare the SiO observations with archival H₂ 1-0 S(1) images and published H₂ echelle spectra. We find that, although the SiO velocities closely match the radial velocities seen in H₂, the distributions of H₂ and SiO emission differ markedly. We attribute the latter to the different excitation conditions required for H₂ and SiO emission, particularly the higher critical density (n_H2∼10⁸/cm3) of the SiO J = 8-7 emission. The kinematic similarities imply that the H₂ and SiO are associated with the same internal working surfaces. We conclude that the SiO J = 8-7 emission has a potential for probing the jet/wind launching region through interferometric observations in the future, particularly for the youngest, most deeply embedded protostars where IR observations are not possible.