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