1. Why Warps ?… Accretion, Recycling, Stimulation ?
NGC 3344
Sancisi 1976

2. Why Warps ?… Accretion, Recycling, Stimulation ?
NGC 3344
Sancisi 1976

3. Warped disks…
NGC 3344
Sky plane

4. Isolated, face-on, L*, Sc
NGC 628
= M74
Kamphuis &
Briggs 1992

5. NGC 628
= M74
Kamphuis &
Briggs 1992
Ring Analysis
Lopsided
Lumpy

6. NGC 628
= M74
Kamphuis &
Briggs 1992
Model Velocity Field
Edge-on View

7. in flattened potential
NGC 628
= M74
Kamphuis &
Briggs 1992
Perpendicular to
inner disk plane
Perspective View
Line of Nodes
regresses
in flattened potential !

8. Which ones ?
Large
Relatively isolated
Kim, de Blok, Briggs

9. in flattened potential
Times Scales:
Orbital Times -> 1Gyr
carries imprint/memory of formation/accretion
Differential Precession
(Differential Rotation)
Angular momentum:
“Corotation” !
Line of Nodes
regresses
in flattened potential

10. Mechanisms: “Primordial Rain” (Binney ~2000)
from Random Directions…
“Cold Mode Accretion” (Kereš et al. 2005, 2009)
streams…
Recirculation/re-accretion
galaxy-galaxy interactions

11. “Cold” gas only Cold Mode of Gas Accretion Kereš et al. 2005, 2009
Simulation
Cold Mode of Gas Accretion
m_p ~106 M⊙, resolution ~500pc (at z=2)
“Cold” gas
only

12. Accretion rate vs Redshift
Kereš et al. 2009
from Simulations
Accretion rate vs Redshift
Cold

13. NGC 1512
NGC 1510

14. Relatively small perturbers spray gas into orbits that remember
NGC 1512
Relatively small perturbers spray gas into orbits that remember
angular momentum of interaction… (doesn’t look like smooth warp)

15. Mechanisms: “Cold Mode Accretion” Recirculation/re-accretion
M83 (Miller et al 2009)
“Cold Mode Accretion”
Recirculation/re-accretion
… need to measure metalicity of gas…
absorption lines against background AGN
HII regions in faint star forming lumps