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Studies of Molecular Outflows

Studies of Molecular Outflows

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Studies of Molecular Outflows

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  1. Studies of Molecular Outflows Hsin-Lun Kuo Department of Physics,NTU Supervisor:Hsien Shang 2002 Summer Students Presentation, ASIAA

  2. Outline • Bipolar Molecular Outflows of YSOs • A Simple Physical Model Based on “Star Formation And The Nature Of Bipolar Outflows”, Shu et al., ApJ 370, March 1991 • Try To Produce Different Shapes of The Lobes Summer Students,ASIAA

  3. Bipolar Molecular Outflows of YSOs • Deeply related to the processes of star formation and early stellar evolution • Observable from UV to radio, best traced by CO emission • Flow sizes: less than 0.1pc ~ several pc • Terminal velocities: a few kms-1 ~ several hundred kms-1 • Kinematical time-scale: 103 ~ 105 yr • Outflowing mass: 10-2 M ~ 102 M Summer Students,ASIAA

  4. Properties of Outflows • Intrinsic or external, large-scale collimation? • “Classical” and “highly collimated” outflows in observations • Collimation factor--axial ratio • Hubble-like law • Jet-like and EHV bullets • Class I and Class 0 YSOs Summer Students,ASIAA

  5. Shu’s “Snowplow” Model • Radiating shocks form a swept-up shell of ambient molecular cloud material • Swept-up and shocked-wind material mixed well • Momentum-driven • Intrinsically collimated by MHD mechanism Summer Students,ASIAA

  6. Equations • Density distribution of an isothermal sphere • Momentum input per steradian Summer Students,ASIAA

  7. Solutions • For momentum conserved winds blowing into 1/r2 density profiles Shell speed Shell position Bipolarity function Summer Students,ASIAA

  8. Constraints • Q(μ) : • P(μ) : • B(μ) : and and and Axial ratio of lobe Summer Students,ASIAA

  9. My “Guess” on P(μ), Q(μ) B(μ) Q(μ) μ P(μ) μ μ Summer Students,ASIAA

  10. Reproducing The Lobes • Axial ratio 3:1 (with [f/2]1/2=0.4 , avw=100 ) Summer Students,ASIAA

  11. Some Trials– 2:1 Q(μ) μ P(μ) μ Summer Students,ASIAA

  12. Some Trials – 4:1 Q(μ) μ P(μ) μ Summer Students,ASIAA

  13. Some Trials – 5:1 Q(μ) μ P(μ) μ Summer Students,ASIAA

  14. Some Trials – 8:1 Q(μ) μ P(μ) μ Summer Students,ASIAA

  15. Some Trials – 10:1 Q(μ) μ P(μ) μ Summer Students,ASIAA

  16. Future Work • Change a few constraints • Make more realistic guesses on P,Q • Considering f , a , vw , t • Compare to observational results of simple outflows Summer Students,ASIAA