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Theoretical Perspectives

Theoretical Perspectives. Amr El-Zant Canadian Institute for Theoretical Astrophysics. Paradigms Lost. Peebles (1980) intro lists (as possible sources of structure formation) ** Magnetohydrodynamic - Thermal – Plasma Instabilities + host of others

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Theoretical Perspectives

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  1. Theoretical Perspectives Amr El-Zant Canadian Institute for Theoretical Astrophysics

  2. Paradigms Lost • Peebles (1980) intro lists (as possible sources of structure formation) ** Magnetohydrodynamic - Thermal – Plasma Instabilities + host of others ** Dead stars etc as probable forms of the dominant dark matter

  3. LCDM • CDM: largely a consequence of clustering and BBN results. It is also simple to deduce its consequences • Cosmological constant: Supernovae and CMB. • But CMB is degenerate! Consistent with Einstein de Sitter and low Hubble constant…

  4. Galaxy and Halo Biasing as Cosmological Constant Probe Evolution of Galaxy-sized halo density as a function of CDM overdensity in an Einstein de Sitter universe (Dekel & Lahav 1999) Z = 0 Z = 1

  5. Cosmological Tools: CDM • Direct simulations • Halo Model(Bertschinger, Peacock and others) - assumes collapsed structures distributed according to linear theory – produces power spectrum well (at least at z=0). • Peak Patch(Bond & Myers) -follows peaks in initial density field with Zeldovich approximation (Lagrangian linear theory) + and ellipsoidal collapse

  6. Correlation functions and the sizes of Collapsed Structures • Dark matter cold  `everything’ is made of collapsed objects: haloes • Smaller structures collapse first  high z most galaxies in one halo while at low z, galaxies tend to share larger halo • Scale and strength of transition changes with time Angle in deg

  7. Feedback and cooling flow suppression • Gas dynamics simulations: generally fail to form proper galaxies (e.g. Disks too small) • Semi analytic models: relatively successful  need proper treatment of feedback • Problem similar to that in cluster cooling flows. Many solutions proposed, e.g.: i) Heating by AGN ii) Conduction (Zakamska & Narayan) iii) Heating from substructure and galaxy motions (El-Zant, Kim & Kamionkowski)

  8. Bars • Probes of epoch when undisturbed cold disks are in place: In CDM  this happens relatively late at z < ~1 (Mo, Mao & White) • Shapes of dark matter haloes around galaxies:  Unmodified CDM haloes unsuitable for hosting long lived bars: El-Zant & Shlosman; Berentzen, Shlosman & Jojee

  9. Bars in Cosmological Haloes

  10. Bars  AGN’s • Bars known to drive gas to central ~ 1kpc • Mechanism driving gas to very centre still in dispute • Useful observational diagnostic: correlations between AGN and bars  AGN’s without bars may indicate other mechanisms: e.g., interactions or triaxial haloes (El-Zant, Begelman & Frank)

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