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Scaling relations of spheroids over cosmic time:

Scaling relations of spheroids over cosmic time:. Tommaso Treu (UCSB). Outline. Use scaling laws (e.g. Fundamental Plane, M-sigma relation) to map the cosmic evolution of the three main constituents of spheroids: Stars Dark matter Supermassive black holes. 1: Stars.

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Scaling relations of spheroids over cosmic time:

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  1. Scaling relations of spheroids over cosmic time: Tommaso Treu (UCSB)

  2. Outline • Use scaling laws (e.g. Fundamental Plane, M-sigma relation) to map the cosmic evolution of the three main constituents of spheroids: • Stars • Dark matter • Supermassive black holes

  3. 1: Stars Treu et al. 1999,2001,2002,2005a,b See di Serego Alighieri & van der Wel’s talks

  4. The Fundamental Plane as a diagnostic of stellar populations • Empirical correlation between size, luminosity and velocity dispersion • Gives “effective M/L” at “effective mass” Dressler et al. 1987; Djorgovski & Davis 1987; Bender Burstein & Faber 1992; Jorgensen et al. 1996

  5. Evolution of Mass to Light ratios • Evolution of mass to light ratio is a function of dynamical mass • More massive galaxies evolve slower than less massive ones, i.e. older stars (“downsizing”) Treu et al. 2005a

  6. Downsizing star formation Log M>11.5 11.5>Log M>11 11>Log M Young stars <1% Young stars ~5% Young stars up to 20-40% Treu et al. 2005b

  7. Stellar populations: conclusions • Stars in massive early-type galaxies are old • Stars in smaller galaxies are younger • Is this “downsizing” compatible with hierarchical models? • Perhaps, if massive galaxies are assembled without forming new stars (AGN feedback?) • But can other properties (e.g. dark halos, BH) be reproduced as well?

  8. 3: Supermassive Black Holes

  9. The local Universe Gebhardt et al. 2001; Tremaine et al. 2002 Ferrarese & Merritt 2001

  10. How do black-holes and spheroids know about each other? • The size of the dynamical sphere of influence of a BH is R~MBH7 / (σ200)2pc ~0.1-10 pc • The size of the spheroid is of order kpc • Typical accretion rates are of order 0.01 solar mass per yr for a 107 M_sun black hole. Mass of black holes could change over a Gyr timescale. • If spheroids evolve by mergers, what makes the BH and spheroids stay on the same correlation?

  11. The distant universe: two problems • Black hole mass: 1” at z=1 is ~8kpc. We CANNOT resolve the sphere of influence, active galaxies are the only option • Velocity dispersion: distant objects are faint and not resolved. If the galaxy is active we CANNOT avoid AGN contamination

  12. The distant universe: a solution, focus on Seyfert 1s • Black hole mass: • Reverberation mapping (Blandford & McKee 1982) does not need spatial resolution. • Empirically calibrated photo-ionization (ECPI: Wandel, Peterson & Malkan 1999) based on reverberation masses • Velocity dispersion: • integrated spectra have enough starlight that with good spectra it is possible to measure the width of stellar absorption features on the “featureless AGN continuum”. Treu, Malkan & Blandford 2004

  13. Measuring velocity dispersion. Woo, Treu, Malkan & Blandford 2006, astro-ph yesterday!

  14. Black-Hole Mass. Empirically Calibrated Photo-Ionization Method • The flux needed to ionize the broad line region scales as L(ion)/r2. Coefficients too hard to compute theoretically • An empirical correlation is found, calibrated using reverberation mapping Broad line region size L (5100AA) Wandel Peterson & Malkan 1999; Kaspi et al. 2000 Kaspi et al. 2005

  15. Black-Hole Mass. Hb width determination • Hb width from single epoch spectra provides a good estimate of the kinematics of the broad line region if constant narrow component is removed. (Vestergaard & Peterson 2006) • Overall uncertainty on BH mass ~0.4 dex

  16. The Black-Hole Mass vs Sigma relation at z=0.36 Woo, Treu, Malkan & Blandford 2006, astro-ph yesterday!

  17. The Black-Hole Mass vs Sigma relation at z=0.36; cosmic evolution? Δlog M BH redshift Δlog MBH = 0.62±0.10±0.25 dex

  18. Conclusions. • Bulges at z=0.36 smaller than their black-hole masses suggest. Three possibilities: • Selection effects • Problems with the ECPI method • Evolution

  19. Recent evolution of (active) bulges? Treu et al. 2006b

  20. Closing remarks: conjectures and predictions.. • Galaxies form initially as blue disks • Major mergers 1) trigger AGN activity, 2) quench star formation, 3) increase the bulge size • The characteristic mass scale decreases with time (‘downsizing’), consistent with that of our galaxies at z=0.36 Log Mtr redshift Hopkins et al. 2006 The M-sigma relation should be already in place for larger masses!

  21. The end

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