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Environmental Influence on Initial Multiplicity? Chris Matzner Toronto

NASA , ESA, Hubble Heritage Team, (STScI / AURA) and P. McCullough (STScI). Jay Lavine and Ali Huang/Adam Block/ NOAO/AURA/NSF. Allan Cook/Adam Block/NOAO/AURA/NSF. Environmental Influence on Initial Multiplicity? Chris Matzner Toronto.

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Environmental Influence on Initial Multiplicity? Chris Matzner Toronto

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  1. NASA, ESA, Hubble Heritage Team, (STScI / AURA) and P. McCullough (STScI) Jay Lavine and Ali Huang/Adam Block/ NOAO/AURA/NSF Allan Cook/Adam Block/NOAO/AURA/NSF Environmental Influence on Initial Multiplicity? Chris Matzner Toronto

  2. How might environmental factors & initial conditions affect: Dimensionless quantities Binary & multiplicity fractions Mass ratios Dimensional quantities Binary separations ?

  3. Dimensional parameters: • B (T or cs) vturb … Dimensionless parameters: r / (density at opacity limit) Turbulent Mach number Turbulent spectral slope Strength of magnetic field relative to gravity Speed of ambipolar drift relative to free-fall MJeans/Msun – if stellar feedback is important

  4. Influence of Temperature - 1 Thermally supported critical state: Mass per unit radius ~ 2cs2/G Possible applications: - at the opacity limit - in the initial state - at the point of H2 dissociation Suggests a ~ Mtot so long as rotation is a characteristic fraction of the sound speed

  5. Influence of Temperature - 2 T & r together determine MJeans = cs3/(Gr)1/2 ~ T2/r ... which determines the mass scale of the IMF. Therefore, the binary properties for an observed M* depend on its value relative to MJeans.

  6. Alves, Lombardi, & Lada 07 Alves et al. Garay et al. Influence of Temperature - 3 Core temperature determines vesc in the critical state This determines how effectively mass is blown back out by an outflow… Since this removes ~ 60% of the matter, it probably has some effect on multiplicity (e.g., by limiting the mass available for accretion onto a companion star)

  7. Influence of Temperature - 4 Temperature sets mass accretion rate ~ cs3/G … which can determine whether disks fragment to produce low-mass compansions However, this is most likely for high-mass stars, or for very wide separations around low-mass stars.

  8. Influence of Magnetic fields Magnetic fields 1. Provide nonthermal support (increasing Teff) 2. Provide coupling between cloud turbulence & core rotation prior to collapse 3. Cause magnetic braking as core contracts 4. Allow for angular momentum to be lost in disk wind Net effect? Probably a decrease in overall angular momentum scale

  9. Influence of Turbulent Strength Turbulence slows collapse globally, and controls which regions actually collapse Probability Dense enough to collapse depends on log(Mach#) r / <r> depends on Mach #, spectral slope

  10. Conclusions • Although star formation is complicated, only a few parameters • are (easily) identified. • Gas temperature is probably the most important at setting • binary separations • Dimensionless properties, like binary fractions and mass ratios, • probably depend primarily on • Mass of system / (characteristic Jeans mass or IMF peak) • Mach number & spectral slope of turbulence • Degree of magnetization

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