Why Warps ?… Accretion, Recycling, Stimulation ?

NGC 3344

Sancisi 1976

Why Warps ?… Accretion, Recycling, Stimulation ?

NGC 3344

Sancisi 1976

Warped disks…

NGC 3344

Sky plane

NGC 628 = M74

Kamphuis & Briggs 1992

Isolated, face-on, L*, Sc

NGC 628 = M74

Kamphuis & Briggs 1992

Ring Analysis

• Lopsided• Lumpy

NGC 628 = M74Kamphuis & Briggs 1992

Model Velocity Field

Edge-on View

NGC 628 = M74Kamphuis & Briggs 1992

Perspective ViewPerpendicular to inner disk plane

Line of NodesLine of Nodes regresses

in flattened potential !

Which ones ?

•Large

•Relatively isolated

Kim, de Blok, Briggs

Line of NodesLine of Nodes regresses

in flattened potential !

• Orbital Times -> 1Gyr• carries imprint/memory of formation/accretion

• Differential Precession

• (Differential Rotation)

Times Scales:

Angular momentum:

• “Corotation”

Mechanisms:

• “Primordial Rain” (Binney ~2000)• from Random Directions…

• “Cold Mode Accretion” (Kereš et al. 2005, 2009)• streams…

• Recirculation/re-accretion

• galaxy-galaxy interactions

m_p ~106 M⊙, resolution ~500pc (at z=2)

Kereš et al. 2005, 2009 Simulation

Cold Mode of Gas Accretion

“Cold” gasonly

Kereš et al. 2009from Simulations Accretion rate vs Redshift

Cold

NGC 1512

NGC 1510

NGC 1512

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

Mechanisms:

• “Cold Mode Accretion”

• Recirculation/re-accretion

… need to measure metalicity of gas… • absorption lines against background AGN• HII regions in faint star forming lumps

M83 (Miller et al 2009)