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Victor P. Debattista

Secular Evolution in Disc Galaxies. Victor P. Debattista. Deconstructing Galaxies…. … into bulge+disc to test for secular evolution of classical bulges and how this affects the M BH - σ e relation

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Victor P. Debattista

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  1. Secular Evolution in Disc Galaxies Victor P. Debattista

  2. Deconstructing Galaxies… • … into bulge+disc to test for secular evolution of classical bulges and how this affects the MBH-σe relation • … in the vertical direction to understand the thin/thick disc dichotomy in the Milky Way

  3. Classical vs Pseudo Bulges CLASSICAL BULGES: Mergers produce elliptical galaxies. In the early universe, disks formed around dwarf ellipticals. Predict: old stars, low rotation, short SF timescales, ellipsoidal morphology, de Vaucouleurs type profiles (Sersic index ~ 4) PSEUDO BULGES: Gas funnelled to the centre by disk processes, forming new stars and central mass concentration Predict: younger stars, high rotation, long SF timescales, disky or boxy morphology, exponential type profile (Sersic index ~ 1)

  4. Drory & Fisher 2007; Fisher & Drory 2008, 2010

  5. The Evolving View of AGN Hosts Schawinski+ 2012 A sample of 140 X-ray selected AGN showed distortions (“mergers”) were no more likely to be ongoing than in a control sample Cisternas+ 2011 Schawinski+ 2011

  6. Semi-analytic models suggest that AGN in discs dominate the AGN luminosity for low mass Hopkins+ 13

  7. 20x Mb 15x Mb 10x Mb 20x Mb 5x Mb No disc The growth of a disk compresses a pre-existing (classical) bulge raising its velocity dispersion Zero mass disc (for scale)

  8. Fitting function following Wolf et al. 2010: The parameters (ϒ,δ) account for the finite-thickness and assumption of fixed effective radius

  9. Data: Gadotti & Kauffmann 2009 Ellipticals Bulges Bulges σ8 σ8 Ellipticals Mass Reff

  10. Data: Gadotti & Kauffmann 2009 Ellipticals Bulges Bulges uncompressed

  11. Exponential Disks? Dutton 2009 Boeker+ 2003

  12. σ8 Rd/Reff D/B D/B and Rd/Re correlate weakly with σe. Neglecting this correlation, the M-σe relation of SMBHs which start out on the relation but fail to grow with this disc is given by: log M = α – β log <σe/σe0> + β log σe

  13. Gültekin+ 2009 Doubling σ requires that M grow by a factor of 16 Gadotti 09

  14. Gültekin+ 2009 sample Expected offset if SMBHs do not grow while discs reform is δα = -0.2 dex δα = 0.08 No offset between bulges now and ellipticals Ellipticals Bulges

  15. Beifiori+ 2009 sample Expected offset if SMBHs do not grow while discs reform is δα = -0.26 dex Bulges Predicted initial dispersions Ellipticals δα = 0.11 Also no offset between bulges now and ellipticals

  16. Barred Galaxies Graham+ 11 Graham 08 But Beifiori et al. 2012 find no offset between barred and unbarred galaxies

  17. All B+D simulations are models of the MW from Widrow+ 08 Bar driven angular momentum redistribution increases the disc mass at the centre, raising σe and causing an offset for the SMBH Hartmann+ 14

  18. Hartmann+ 14 Classical bulges δα = -0.19 ± 0.20 Pseudo bulges • δα = -0.73 ± 0.09 Sample of McConnell & Ma 13 10 other galaxies with no reliable bulge classification

  19. Full Near circular ∆L L E = p L JR = (p -) L/ R But negligible heating associated with the migration Radius Sellwood & Binney 2002

  20. Gilmore & Reid 1983 Schoenrich & Binney 09ab Rform Roškar+ 08

  21. Roškar+13 Thin disk Predictions from Schönrich & Binney 12 Plotted for stars 5-6 Gyr old Thick disk Accretion: Abadi+03; thickening: Quinn+93; gas rich mergers: Brook+05; direct gas formation: Stinson+13; Bird+13; clump heating: Bournaud+07; resonant capture: Sridhar+96 Solway+ 2012

  22. Ruchti+ 11 Migration can give rise to a thick disc with density, kinematic, metallicity and abundance patterns not inconsistent with the observed Loebman+ 11 Roškar+ 13

  23. SDSS at Thin-Thick Transition Decreasing metallicity and vrot with height [Fe/H] VY [km/s] |z| [kpc] VY [km/s] Photometric [Fe/H] z [pc] Data from SDSS Ivezic+ 08; Bond+ 10

  24. Age, velocity and metallicity all correlate with height above the mid-plane. But there is little correlation between velocity and metallicity, as found by SDSS Age [Gyr] Vy [km/s] Vy [km/s] [Fe/H] [Fe/H] z [kpc]

  25. Liu & van de Ven 2012 Dierickx+ 10, Wilson+ 11 Bovy+ 2012abc Sales+ 2009

  26. Conclusions • Discs growing around pre-existing bulges compress them and raise their velocity dispersion. This implies SMBHs in classical bulges must grow on average by 50-80% to remain on the MBH-σe relation. A comparison between the MBH-σe relations of elliptical galaxies and classical bulges finds no offset. Bar evolution also compresses the bulge, and there is evidence that barred galaxies are offset from the MBH-σe relation. • The thick disc in the MW may have been substantially contaminated by migrated thin disc stars. A thin/thick disc dichotomy can easily arise as a result of migration. Some evidence for an unmigrated population can be recovered from the distribution of orbital eccentricities.

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