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Why Warps ?… Accretion, Recycling , Stimulation ?. NGC 3344. Sancisi 1976. Why Warps ?… Accretion, Recycling , Stimulation ?. NGC 3344. Sancisi 1976. Sky plane. Warped disks… NGC 3344 . Isolated, face-on, L*, Sc. NGC 628 = M74 Kamphuis & Briggs 1992. NGC 628
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Why Warps ?… Accretion, Recycling, Stimulation ? NGC 3344 Sancisi 1976
Why Warps ?… Accretion, Recycling, Stimulation ? NGC 3344 Sancisi 1976
Sky plane Warped disks… NGC 3344
Isolated, face-on, L*, Sc NGC 628 = M74 Kamphuis & Briggs 1992
NGC 628 = M74 Kamphuis & Briggs 1992 Ring Analysis • Lopsided • Lumpy
Edge-on View NGC 628 = M74 Kamphuis & Briggs 1992 Model Velocity Field
NGC 628 = M74 Kamphuis & Briggs 1992 Perpendicular to inner disk plane Perspective View ! Line of Nodes regresses in flattened potential
Which ones ? • Large • Relatively isolated Kim, de Blok, Briggs
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
Mechanisms: • “Primordial Rain”(Binney ~2000) • from Random Directions… • “Cold Mode Accretion”(Kereš et al. 2005, 2009) • streams… • Recirculation/re-accretion • galaxy-galaxy interactions
Cold Mode of Gas Accretion Kereš et al. 2005, 2009 Simulation m_p ~106 M⊙, resolution ~500pc (at z=2) “Cold” gas only
Kereš et al. 2009 from 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: 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