1. Molecular Outflows in Young Stellar Objects
Keping Qiu, Silvia Leurini
Max-Planck-Institute for Radioastronomy

2. the process of star formation is characterized by:
Accretion of mass from the envelope (disk)
Powerful events of mass loss (jets/outflows)
Early stages of star formation are interesting to understand how stars of different masses form. Molecular outflows extends up to several pc and are easy to observe (review from Arce et al. 2007, Planets and Protostars V)
T Tauri stars are ideal target to study the jet launching zone, since earlier stages are too embedded.
See reviews from Ray et al. Planets and Protostars V; Bacciotti 2009

3. Models of low-mass molecular outflows
X-Wind
Disk-Wind
Credit: M. Cai
Fendt (2009)‏
Low-mass molecular outflows are thought to be entrained/swept-up by a magneto-centrifugally driven wind — X-wind or disk-wind

4. An archetypical protostellar outflow ―HH 211
Gueth & Guilloteau (1999)‏
Palau et al. (2006)‏

5. Relevant Parameters
Low-Mass Outflows (typical values from CO observations):
Size: ~0.1 to 1 pc
Mass: ~0.01 to 1 Msun
Velocity: ~10 to 100 km/s
Mass loss: <10-5 Msun per yr
Momentum: ~0.1 to 10 Msun•km/s
Momentum loss: ~10-6 to 10-4 Msun•km/s per yr
The velocity of the underlying jet or wind, from optical/IR spectroscopy and radio proper motion measurements, is typically a few 100 km/s.
Therefore under momentum-driven assumption, the mass, mass loss rate, and momentum loss rate would be about one order of magnitude lower for the underlying jet or wind.

6. Massive molecular outflows
Beuther et al. (2002)
Mass and energetics orders of magnitude greater than those in low-mass outflows
Some of our interferometer studies:
Qiu et al. (2009); Qiu & Zhang (2009); Leurini et al. (2009)

7. Two-component outflows in the X-wind model