Secular Evolution of Galactic Disks

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Secular Evolution of Secular Evolution of Galactic Disks Galactic Disks James Binney James Binney Oxford University Oxford University

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Secular Evolution of Galactic Disks. James Binney Oxford University. Evidence for Evolution. Hipparcos data for solar nhd Heating driven by (a) spiral structure (b) massive clouds. (Dehnen & Binney 98). - PowerPoint PPT Presentation

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  • Secular Evolution of Galactic DisksJames BinneyOxford University

  • Evidence for EvolutionHipparcos data for solar nhdHeating driven by (a) spiral structure (b) massive clouds

    (Dehnen & Binney 98)

  • Effect of Spiral Structure(Sellwood & Binney 02)Changes in angular momentum heat:

    L important only at resonancesAt LR soEffective heating by transient ss: then resonances broad and/or moving

  • Numerical Experiments

  • Conclude: L changes dominated by corotation, where no associated heating

    Mechanism: horse-shoesNon-analytic

  • Unconstrained Simulation

  • Much radial migrationBut keeps cool

  • Evidence for MigrationSun higher Z than local ISM even now

    No correlation of Z with age (Edvardsson et al 93)Also 29Si/28Si in presolar dust grains suggest enrichment at R~4 kpc (Clayton 97)

  • Effect on n(v)Hipparcos n(v) full of structure (Dehnen 98)

  • Largest feature probably effect of bar (Raboud et al 98; Dehnen 99)

    Spirals probably responsible for other structure (De Simone, Wu & Tremaine 04)

  • Back to HeatingIts a sideshow!Its driven by spiralsIt happens at ILRClouds feed E into z motionBut make negligible contribution to heating: from R/z, JR|wave~9.5JR|cloud (Jenkins & Binney 90)

  • Models of Heating(Binney, Dehnen & Bertelli 00)Parameterize IMF and SFR

    Get B-V and from Padua ss modelsResults depend on Z distribution

  • ConclusionsTransient spiral structure churns disks through action at CRDirectly evident in n(v)Fundamental for chemical evolutionExplains Z distribution near Sun(Small) L changes at ILR heat diskCloud scattering transfers E to zFrom (B-V) get SFR~const and ~t1/3