Detection of SiO emission from a massive dense cold core

We report the detection of the SiO (J = 2−1) transition from the massive cold dense core G333.125−0.562. The core remains undetected at wavelengths shorter than 70 μm and has compact 1.2-mm dust continuum. The SiO emission is localized to the core. The observations are part of a continuing multi-molecular line survey of the giant molecular cloud G333. Other detected molecules in the core include 13CO, C18O, CS, HCO+, HCN, HNC, CH3OH, N2H+, SO, HC3N, NH3, and some of their isotopes. In addition, from NH3 (1,1) and (2,2) inversion lines, we obtain a temperature of 13 K. From fitting to the spectral energy distribution we obtain a colour temperature of 18 K and a gas mass of 2 × 103 M . We have also detected a 22-GHz water maser in the core, together with methanol maser emission, suggesting that the core will host massive star formation. We hypothesize that the SiO emission arises from shocks associated with an outflow in the cold core.