The near environment of a young star is complex and dynamic, with gas and dust infalling from the parent molecular core via a circumstellar disk, at the same time as highly-collimated bipolar jets drive some fraction of that material away again from the star. Outflows have a crucial role to play in the star formation process, removing excess angular momentum from the infalling material allowing it to accrete onto the central star, clearing the protostellar envelope and thus perhaps helping set the final stellar mass, and injecting turbulent energy into the ambient molecular cloud, providing support against collapse to form further stars. The jets and outflows are collimated close to the young star in a zone that is highly obscured by surrounding dust, and thus high angular resolution infrared, millimetre, and radio observations are required. Important diagnostics include water and silicon monoxide maser emission from near the base of the flow, shocked molecular hydrogen emission as the jet interacts with the surrounding medium, and carbon monoxide emission from the swept-up flows. Here we outline the current paradigm describing how outflows are driven from young stars and how they interact with their environment, showing illustrative examples from high angular resolution observations made with the HST, VLT, VLA, and VLBI. Finally, we discuss how future facilities including the NGST and ALMA will allow us a yet deeper, closer, and more detailed view of this important feedback process.
Galaxies and their Constituents at the Highest Angular Resolutions
- Pub Date:
- January 2001