Kinematics Dynamics of Disk Galaxies James Binney Oxford

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

& structures it Famaey et al 04 Dehnen 1998

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

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

S&B (02) • E- p. L=const • Stars cross CR on horse-shoe orbits

S&B (02) • Heating restricted to ILR

Unconstrained simulation NGC 4062 in H Puerari et al 2000

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

(04)

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

Warps NGC 5055 by Tom Oosterloo • 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’)

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

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

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

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

• 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?

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

Gas • Gas is the source of new stars and thus spirals • How much is there? • How much H 2? M 101 HI + FUV (Braun) • HI correlated with FUV • Is HI just a photo-dissociated skin on H 2? (Allen et al 97; Allen 2004)

Stars far out • Young stars (& dust) seen at 23 -33 kpc in M 31 (Cuillandre et al 02) • Stars traced to 10 Rd in NGC 300 (Bland-Hawthorn et al 05) • Stars surely form from cold dense gas • Thus from H 2 • Is there serious gas mass in extended disks?

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

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 H 2 outside the optical disk; could it be dynamically important?