310 likes | 406 Views
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
E N D
ONC: kinematics etc. Lee Hartmann, University of Michigan Andi Burkert, John Tobin, Marina Kounkel, Fred Adams
large-scale AV map Orion A/B Rowles & Froebrich 2009
acceleration Non-linear acceleration vs. position in filaments (Bonnell et al 1992)- “edge effect” in ~ 1 dimension make concentrations (clusters) at ends
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)
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
Carpenter + 2001 RV 1 pc 1pc/2 km/s ~ 0.5 Myr 1 pc HH98, e ~ 0.3
spherical, subvirial elongated, subvirial, major axis elongated, subvirial, 30o elongated, virial, 30o
caustic? why only one side? asymmetry of mass distribution?
histogram = * 13CO Jones & Walker 88 1D FWHM (proper motion)
Foreground contamination? ONC Briceno et al.
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
What accounts for the stellar/13CO velocity offset? evaporation/blowout of dense gas? < works for ONC/1977(?), but what about OMC 2/3?
What accounts for the stellar/13CO velocity offset? gravitational collapse + dissipation to make narrow filament? < OMC 2/3?
crazy idea; “some stars left behind?” later generation? 1st generation less redshifted (running into denser gas)? need to understand time evolution of region
kinematics: not equilibrium – constraint on timescales? gravity is important, but details uncertain need to understand time evolution of region ?
histogram = * 13CO foreground 1a pop?
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
Simulations of cloud flow with gravity show accelerating collapse Vazquez-S. Heitsch ages of ONC stars??
Orion Nebula region Megeath et al. 2012 T Tauri stars Protostars: collapse down to extremely dense filament Pgrav >> P(ISM)