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Lee Hartmann, University of Michigan

ONC: kinematics etc. Lee Hartmann, University of Michigan. Andi Burkert, John Tobin, Marina Kounkel, Fred Adams. large-scale A V map. Orion A/B. Rowles & Froebrich 2009. acceleration . Non-linear acceleration vs. position in filaments

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Lee Hartmann, University of Michigan

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  1. ONC: kinematics etc. Lee Hartmann, University of Michigan Andi Burkert, John Tobin, Marina Kounkel, Fred Adams

  2. large-scale AV map Orion A/B Rowles & Froebrich 2009

  3. acceleration Non-linear acceleration vs. position in filaments (Bonnell et al 1992)- “edge effect” in ~ 1 dimension make concentrations (clusters) at ends

  4. Evidence for large-scale gravity; focusing in elongated clouds causes clusters to form preferentially at ends (Bonnell; Burkert & LH, “focal points”) Orion A/B Pipe (Lombardi) NGC 2264 (Sung+) Perseus (Rebull)

  5. Orion A (Hartmann & Burkert 2007); elliptical sheet, smooth density gradient, ~ 2 Myr evolution 13CO, Bally et al. cluster Short radius of curvature results in extra mass concentrations  assemble cluster gas/stars

  6. Carpenter + 2001 RV 1 pc 1pc/2 km/s ~ 0.5 Myr 1 pc HH98, e ~ 0.3

  7. (2GM/R)1/2 ~ 3 km/s (4000 M☉/4 pc)1/2

  8. fixed gas potential; N body

  9. spherical, subvirial elongated, subvirial, major axis elongated, subvirial, 30o elongated, virial, 30o

  10. Megeath et al.

  11. caustic? why only one side? asymmetry of mass distribution?

  12. histogram = * 13CO Jones & Walker 88 1D FWHM (proper motion)

  13. Foreground contamination? ONC Briceno et al.

  14. What accounts for the stellar/13CO velocity offset? stellar motions? stars moving away from us too extincted for optical study? < problem? velocity widths already seem to be ≥ Jones/Walker p.m. dispersion

  15. What accounts for the stellar/13CO velocity offset? evaporation/blowout of dense gas? < works for ONC/1977(?), but what about OMC 2/3?

  16. What accounts for the stellar/13CO velocity offset? gravitational collapse + dissipation to make narrow filament? < OMC 2/3?

  17. crazy idea; “some stars left behind?” later generation? 1st generation less redshifted (running into denser gas)? need to understand time evolution of region

  18. NGC 2264 – Kounkel, Tobin et al. in prep

  19. kinematics: not equilibrium – constraint on timescales? gravity is important, but details uncertain need to understand time evolution of region ?

  20. histogram = * 13CO foreground 1a pop?

  21. Velocity fields not particularly random (G x 105 M(sun)/15 pc)1/2 ~ 5 km/s how do you avoid gravitationally-generated motion?? 30 pc Orion A 13CO; Bally et al. 1987

  22. factor in efficiency; pre-existing cloud structure?

  23. Simulations of cloud flow with gravity show accelerating collapse Vazquez-S. Heitsch ages of ONC stars??

  24. Orion Nebula region Megeath et al. 2012 T Tauri stars Protostars: collapse down to extremely dense filament Pgrav >> P(ISM)

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