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Dynamics of Galactic Nuclei

Dynamics of Galactic Nuclei. MODEST 6 Evanston, 2005. M B < -20. Σ. Σ ~ R - Γ Γ < 0.5. Sersic n > 4. R. M B < -20. Σ. Σ ~ R - Γ Γ < 0.5. Sersic n > 4. R. Sersic n ≈ 4. M B < -20. -18 < M B < -20. Σ ~ R - Γ 0.5 < Γ < 1.2. Σ. Σ ~ R - Γ Γ < 0.5. Sersic n > 4.

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Dynamics of Galactic Nuclei

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  1. Dynamics of Galactic Nuclei MODEST 6 Evanston, 2005

  2. MB < -20 Σ Σ ~ R-ΓΓ < 0.5 Sersic n > 4 R

  3. MB < -20 Σ Σ ~ R-ΓΓ < 0.5 Sersic n > 4 R

  4. Sersic n ≈ 4 MB < -20 -18 < MB < -20 Σ ~ R-Γ0.5 < Γ < 1.2 Σ Σ ~ R-ΓΓ < 0.5 Sersic n > 4 R R

  5. Sersic n ≈ 4 MB < -20 -18 < MB < -20 Σ ~ R-Γ0.5 < Γ < 1.2 Σ Σ ~ R-ΓΓ < 0.5 Sersic n > 4 R R

  6. Sersic n ≈ 4 Sersic n < 4 MB < -20 -18 < MB < -20 MB < -18 ? Σ ~ R-Γ0.5 < Γ < 1.2 PSF Σ Σ ~ R-ΓΓ < 0.5 Sersic n > 4 R R R

  7. Sersic n ≈ 4 Sersic n < 4 MB < -20 -18 < MB < -20 MB < -18 ? Σ ~ R-Γ0.5 < Γ < 1.2 PSF Σ Σ ~ R-ΓΓ < 0.5 Sersic n > 4 R R R

  8. Local-Group-Galaxy Density Profiles rh Genzel et al. 2003 Lauer et al. 1998

  9. Nuclear Relaxation Times ● BH mass from M-sigma relation ○ BH mass from M-L relation * “Core” galaxies Luminosity profile data: Coté et al. ACS Virgo Survey

  10. Nuclear Relaxation Times M32 Relaxation times begin to drop below 1010 yr for MB > -19

  11. “Collisional” Cusp In ~ one relaxation time Tr , a power-law cusp of slope ρ ~ r -7/4 grows around a black hole, within a distance ~rh: rh≡ GMbh/σ2 (Bahcall & Wolf 1976). Preto, Merritt & Spurzem 2004

  12. “Collisional” Cusp In ~ one relaxation time Tr , a power-law cusp of slope ρ ~ r -7/4 grows around a black hole, within a distance ~rh: rh≡ GMbh/σ2 (Bahcall & Wolf 1976). At the Galactic center, rh≈ 2 pc, Tr (rh) ≈ 3 Gyr. rh Preto, Merritt & Spurzem 2004 Baumgardt et al. 2004

  13. Schödel et al. (in prep.) Milky Way Density Profile Σ ~ R-3/4 rh ≈ 50"

  14. Black Hole Feeding Rates • Based on: • “Nuker” luminosity profiles • Cohn-Kulsrud loss- cone boundary conditions • (Not quite self-consistent.) MW Wang & Merritt 2004

  15. Nuclear Expansion Loss of stars via tidal disruption represents a heatsource for the nucleus, causing it to expand. The expansion time scale is ~Tr . (Shapiro 1977) This expansion may be described by the self-similar, post-collapse solutions of Henon, Heggie and others. → Dense nuclei were once denser. Baumgardt et al. 2005

  16. Low-Density Nuclei Bright galaxies have (non-isothermal) “cores” This is plausibly due to mergers, and the “scouring” effects of binary SMBHs. NGC 3348 A. Graham 2004

  17. Binary Black Holes Galaxies merge Binary forms Binary decays, via:-- ejection of stars-- interaction with gas

  18. a Binary Evolution in Power-Law Nucleus Szell, Merritt & Mikkola 2005

  19. a Binary Evolution in Power-Law Nucleus Also:Makino & Funato 2004Berczik, Merritt & Spurzem 2005 Szell, Merritt & Mikkola 2005

  20. What Values of N are Required? N fixes the ratio of relaxation time to crossingtime: Any process that depends on the separation of the two time scales, requires a large N.

  21. In loss-cone problems,this requirement is more severe. Stars are scattered by other stars into the loss cone, where they can interact with the central object(s). star θ Scattering time is ~θ2Trelax<<Trelax and separation of the two time scales requires Trelax>>θ-2Tcross single or binary black hole

  22. Minimum Number of Stars Required to “Resolve” Central Object Minimum N required to “resolve” central object. rt = size of central object rh = influence radius of black hole(s) Binary BH

  23. a Binary Evolution in Power-Law Nucleus Full loss cone Szell, Merritt & Mikkola 2005 Empty loss cone

  24. Binary Evolution in Plummer – Law Galaxy Berczik, Merritt & Spurzem 2005

  25. eccentricity time Eccentricity Evolution N =8K16K32K 65K131K262K Szell, Merritt & Mikkola 2005

  26. eccentricity time Eccentricity Evolution N =8K16K32K 65K131K262K Szell, Merritt & Mikkola 2005

  27. “Mass Deficits” “Mass deficit” produced by equal-mass binary. N =8K16K32K 65K131K262K Szell, Merritt & Mikkola 2005

  28. Cusp Regeneration After being destroyed by a binary SBH, a power-law cusp can regenerate itself. Condition: relaxation time after cusp destruction must be < 1010 yr. • Initial binary: m2/m1 = 0.1 • Tr(rh) = 340 Merritt & Szell 2005

  29. For the Future… • Algorithms/hardware for N >>106, direct-integration algorithms. • Further development of chain-regularization algorithms for BH(s) • Evolution of binary SBHs, starting from realistic initial conditions • “Mass deficits” produced by multiple mergers • Better understanding of SBH-driven nuclear expansion • Interplay of dark and luminous matter • Effects of mass spectra • Feeding rates in non-relaxed nuclei • -- ….. !

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