The Environment of High-Mass Young Stellar Objects

Using high-resolution infrared CO spectroscopy new results have been obtained on the environment of high-mass young stellar objects (YSOs). In particular, a new class of neutral, warm and den se outflows has been discovered. The infrared outflows appear a general phenomenon of the activity of high-mass YSOs. With well-defined and often multiple velocities they seem to correspond to episodic and violent mass-loss events from the central source. In addition, a shell of warm, quiescent gas, is formed near the massive star. All these dynamical elements influence the chemistry inside the giant molecular clouds. Beside CO in solid and in gas phase, detection in the infrared has been attempted of simple molecules like CH4, C2H2, H2O and ion H3 + toward few of these sources.