Zurück zur ersten Seite Dynamical Decay of Young Few-Body Clusters and “Isolated“ T Tauri Stars Michael Sterzik, ESO Richard Durisen, Indiana University Brian Pickett, Valparaiso University n Scenario: Disintegrating Multiples in Early Stellar Evolution n Results and Predictions of Numerical Simulations n Are there “Isolated“ TTS? “Run-Away“ TTS? Ejected BDs?

Zurück zur ersten Seite Core Fragmentation: Observations Molecular Cloud Cores fragment down to scales of <0.1pc Core mass spectrum resembles stellar IMF Andre et al., 2000, Protostars and Planets IV Serpens core: Testi & Sargent, 2000, ApJL

Zurück zur ersten Seite Fragmentation during Cloud Collapse n During 1st (isothermal) collapse n M J  M sol n R J  A.U. n difficult in spherical, centrally condensed cores, but: n prolate cores with gaussian, or uniform,  profiles fragment ! n simulations: Bonnell, Boss, Burkert, Bodenheimer, Nelson, Monaghan, Klein, Sigalotti Phases of cloud collapse

Zurück zur ersten Seite Scenario  system scale  0.1 pc   300AU

Zurück zur ersten Seite Example: Burrau‘s problem n „Pythogorean“ 3 body problem (Burrau 1913) n Solution by Szebehely & Peters (1967)

Zurück zur ersten Seite Burrau‘s problem with CHAIN

Zurück zur ersten Seite Qualitative features of disintegrating few-body systems n Lifetime: tens of crossing times (T cr = GM tot 5/2 / E 0 3/2 ) n Encounters cause energy redistiribution: tight subsystems and escapers n Remnant binaries consists of most massive bodies („dynamical biasing“), rel. high eccentricity n Escapers are single, and less massive n Formation of very close binaries rare n Higher-order systems are hierarchically organized

Zurück zur ersten Seite Physical Scaling - E tot /M tot = const. v vir = const. - R vir = 125 AU and M tot = 3M : v vir = 3.3 km/sec Dispersion Velocities  HUGE differences in recoil velocities of S and B‘s  dispersion velocities can be significant >v vir

Zurück zur ersten Seite System Scale and Binary Separation Distributions  post-collapse separation distribution broadened  post-collapse scale reduced by  5-10  BSD depend on primary mass  tends to agree (qualitatively) with DM ! Initial mean Separations Final Binary Separation Distribution

Zurück zur ersten Seite Application: variation of IMF (Sterzik & Durisen 1995, 1998, 1999; Durisen, Sterzik, Pickett 2000, 2001) n Initial condition: N=4, spherical, cold (  =  =0) n compare „two-step“ IMFs incl BDs (stellar MF is drawn from a clump MF) CMS4-BDstdCMS4-BDenh

Zurück zur ersten Seite Single and Binary fractions

Zurück zur ersten Seite Spatial Evolution of a loose Cluster n Initial star formation volume (R SFR = 10pc) n Continuous star formation rate (10 M sol /My) n Populate with results from decay calcs n Propagate locations according to system velocities n Compare with fiducial gaussian vel. distribution

Zurück zur ersten Seite FiducialFew-Body Decay „Kinematical Relaxation“: B and T segregate from S and bd „isolated“ run-away stars are preferentially S and low-mass Symbol size = log(System mass) Single Binary Triple browndwarf

Zurück zur ersten Seite Where are raTTS / isolated TTS? The large scale spatial distribution of ROSAT selected young stellar candidates in Orion

Zurück zur ersten Seite Protostellar Jets... n Multiplicity in HH111: decaying triple system (Reipurth et al, 1999, A&AL) n highest BF in sources of giant HH flows n HH activity related to binary orbit modulation? n IRC binaries (!), accompanied by visible TTS n TMR-1C: „ejected protoplanet“ (Terebey et al. 1998, Petr, Cuby, Sterzik, 2000)

Zurück zur ersten Seite Conclusions n few-body decay is likely in early stellar evolution n stellar dynamics approximates the evolution n two-step IMF can reproduce obsvd. trends in BF & MR n cluster decay broadens and reduces scale by 10 n velocity distributions are nonGaussian, high vel. Tails n spatial segregation of multiples from singles n field brown dwarfs are single, with significant velocities Star formation during a paradigm shift from binary to multiple star formation