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Kinematics & Dynamics of Disk Galaxies

Kinematics & Dynamics of Disk Galaxies. James Binney Oxford University. Outline. Spiral structure Warps Mass of the gas disk Baryon domination Bar-halo interaction Bars & pseudobulges. Spiral Structure. More than icing on the cake It heats the disk. Dehnen & Binney 98.

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Kinematics & Dynamics of Disk Galaxies

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  1. Kinematics & Dynamics of Disk Galaxies James Binney Oxford University

  2. Outline • Spiral structure • Warps • Mass of the gas disk • Baryon domination • Bar-halo interaction • Bars & pseudobulges

  3. Spiral Structure • More than icing on the cake • It heats the disk Dehnen & Binney 98

  4. & structures it Famaey et al 04 Dehnen 1998

  5. Rag-bag streams • Hyades-Pleiades gp (red) not coeval • Sirius gp (magenta) lower Z and even wider dispersed ages • Hercules gp (green) Si gp

  6. Stream assembly • Sellwood & Binney (02) Set up disk to excite single transient pattern

  7. S&B (02) • E-pL=const • Stars cross CR on horse-shoe orbits

  8. S&B (02) • Heating restricted to ILR

  9. Unconstrained simulation NGC 4062 in H Puerari et al 2000

  10. S&B (02) • Result: much migration • Impacts Z distribution in solar nhd

  11. (04)

  12. Impact on gas • Gas clouds should also migrate • Will reduce metallicity gradients • Need to revisit models of chemical evolution (Schoenrich 06)

  13. Warps • Warps long thought to be probe of DM halos (Binney 78…) • Key fact: halos are responsive • Halo @ r quickly aligns with disk @ r (& becomes misaligned with halo at r’) NGC 5055 by Tom Oosterloo

  14. Consequently, normal-mode theory fails (Binney Jiang & Dutta 98) Lines of nodes

  15. BJD (98) • Warp doesn’t damp; it winds up

  16. So what is the answer? • Jiang & Binney (99) generated a warp by adding halo particles in an inclined torus • Shen & Sellwood (05) do a similar job with higher precision: larger disk, of stars not rings, tenfold increase in # halo stars, larger torus

  17. Shen & Sellwood (05) NGC 4013 from Bottema (96)

  18. Key is to apply torque to outer disk by distorting outer halo • Changes in cosmic inflow pattern will do this • Precession of torqued disk/inner-halo generates leading spiral in outer lon • Briggs (90) rules obeyed • Has MOND an equally plausible explanation?

  19. The Gas Disk • Is the gas disk really the more fundamental? NGC 2403 by Tom Oosterloo

  20. Gas • Gas is the source of new stars and thus spirals • How much is there? • How much H2? • HI correlated with FUV • Is HI just a photo-dissociated skin on H2? (Allen et al 97; Allen 2004) M101 HI + FUV (Braun)

  21. Stars far out • Young stars (& dust) seen at 23-33 kpc in M31 (Cuillandre et al 02) • Stars traced to 10Rd in NGC 300 (Bland-Hawthorn et al 05) • Stars surely form from cold dense gas • Thus from H2 • Is there serious gas mass in extended disks?

  22. Remember HI scaling (Swaters 99, Hoekstra et al 01)

  23. Conclusions • Spirals don’t just heat, they churn the disk • Effects visible in local n(v) • Phenomenon has big implications for (i) diagnosing local spiral structure (ii) models of chemical evolution • Warps almost certainly reflect misalignment of inner & outer halo • Plausibly generated by cosmic infall • There must be H2 outside the optical disk; could it be dynamically important?

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