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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

Kinematics & Dynamics of Disk Galaxies

James Binney

Oxford University

outline
Outline
  • Spiral structure
  • Warps
  • Mass of the gas disk
  • Baryon domination
  • Bar-halo interaction
  • Bars & pseudobulges
spiral structure
Spiral Structure
  • More than icing on the cake
  • It heats the disk

Dehnen & Binney 98

structures it
& structures it

Famaey et al 04

Dehnen 1998

rag bag streams
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
Stream assembly
  • Sellwood & Binney (02) Set up disk to excite single transient pattern
s b 02
S&B (02)
  • E-pL=const
  • Stars cross CR

on horse-shoe orbits

s b 021
S&B (02)
  • Heating restricted to ILR
slide9

Unconstrained simulation

NGC 4062 in H

Puerari et al 2000

s b 022
S&B (02)
  • Result: much migration
  • Impacts Z distribution in solar nhd
impact on gas
Impact on gas
  • Gas clouds should also migrate
  • Will reduce metallicity gradients
  • Need to revisit models of chemical evolution (Schoenrich 06)
warps
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

bjd 98
BJD (98)
  • Warp doesn’t damp; it winds up
so what is the answer
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
Shen & Sellwood (05)

NGC 4013 from Bottema (96)

slide18
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
The Gas Disk
  • Is the gas disk really the more fundamental?

NGC 2403 by Tom Oosterloo

slide20
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)

stars far out
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?
conclusions
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?