Secular Evolution of Galactic Disks
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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
Transcript of Secular Evolution of Galactic Disks
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Secular Evolution of Galactic DisksJames BinneyOxford University
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Evidence for EvolutionHipparcos data for solar nhdHeating driven by (a) spiral structure (b) massive clouds
(Dehnen & Binney 98)
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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
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Numerical Experiments
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Conclude: L changes dominated by corotation, where no associated heating
Mechanism: horse-shoesNon-analytic
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Unconstrained Simulation
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Much radial migrationBut keeps cool
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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)
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Effect on n(v)Hipparcos n(v) full of structure (Dehnen 98)
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Largest feature probably effect of bar (Raboud et al 98; Dehnen 99)
Spirals probably responsible for other structure (De Simone, Wu & Tremaine 04)
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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)
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Models of Heating(Binney, Dehnen & Bertelli 00)Parameterize IMF and SFR
Get B-V and from Padua ss modelsResults depend on Z distribution
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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
