scaling relations of spheroids over cosmic time:
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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:
1. Stars2. Dark matter3. Supermassive black holes
1: Stars
Treu et al. 1999,2001,2002,2005a,bSee di Serego Alighieri & van der Wel’s talks
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
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
Downsizing star formation
Treu et al. 2005b
Young stars <1% Young stars ~5% Young stars up to 20-40%
Log M>11.5 11.5>Log M>11 11>Log M
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?
3: Supermassive Black Holes
The local Universe
Gebhardt et al. 2001; Tremaine et al. 2002 Ferrarese & Merritt 2001
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?
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
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
Measuring velocity dispersion.
Woo, Treu, Malkan & Blandford 2006, astro-ph yesterday!
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 Wandel Peterson & Malkan 1999; Kaspi et al.
2000Kaspi et al. 2005
L (5100AA)
Bro
ad li
ne r
egio
n si
ze
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
The Black-Hole Mass vs Sigma relation at z=0.36
Woo, Treu, Malkan & Blandford 2006, astro-ph yesterday!
The Black-Hole Mass vs Sigma relation at z=0.36; cosmic evolution?
Δlog MBH = 0.62±0.10±0.25 dex
redshift
Δlog
M
BH
Conclusions.
• Bulges at z=0.36 smaller than their black-hole masses suggest. Three possibilities:1. Selection effects2. Problems with the ECPI method 3. Evolution
Recent evolution of (active) bulges?
Treu et al. 2006b
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 Hopkins et al. 2006
redshift
Log
M
tr
The M-sigma relation should be already in place for larger masses!
The end