Scaling relations of spheroids overcosmic time:
Tommaso Treu (UCSB)
Outline
•Use scaling laws (e.g. Fundamental Plane,M-sigma relation) to map the cosmicevolution of the three main constituents ofspheroids:
1.Stars
2.Dark matter
3.Supermassive black holes
1: Stars
Treu et al. 1999,2001,2002,2005a,b
See di Serego Alighieri & van der Wel’s talks
The Fundamental Plane as adiagnostic of stellar populations
•Empiricalcorrelationbetween size,luminosity andvelocitydispersion
•Gives “effectiveM/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 tolight ratio is afunction ofdynamical mass
•More massivegalaxies evolveslower than lessmassive 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 withhierarchical models?
–Perhaps, if massive galaxies are assembledwithout 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 spheroidsknow about each other?
•The size of the dynamical sphere of influence of aBH 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 solarmass per yr for a 107 M_sun black hole. Mass ofblack holes could change over a Gyr timescale.
•If spheroids evolve by mergers, what makes theBH and spheroids stay on the same correlation?
The distant universe:two problems
•Black hole mass: 1” at z=1 is ~8kpc. WeCANNOT resolve the sphere of influence,active galaxies are the only option
•Velocity dispersion: distant objects are faintand not resolved. If the galaxy is active weCANNOT avoid AGN contamination
The distant universe:a solution, focus on Seyfert 1s
•Black hole mass:
–Reverberation mapping (Blandford & McKee 1982) doesnot 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 goodspectra it is possible to measure the width of stellarabsorption features on the “featureless AGN continuum”.
Treu, Malkan & Blandford 2004
Measuring velocity dispersion.
Woo, Treu, Malkan & Blandford 2006, astro-ph yesterday!
Black-Hole Mass. EmpiricallyCalibrated Photo-Ionization Method
•The flux needed toionize the broad lineregion scales asL(ion)/r2. Coefficientstoo hard to computetheoretically
•An empiricalcorrelation is found,calibrated usingreverberation mapping
Wandel Peterson & Malkan 1999; Kaspi et al. 2000
Kaspi et al. 2005
L (5100AA)
Broad line region size
Black-Hole Mass.Hb width determination
•Hb width from singleepoch spectra provides agood estimate of thekinematics of the broadline region if constantnarrow component isremoved. (Vestergaard &Peterson 2006)
•Overall uncertainty onBH mass ~0.4 dex
The Black-Hole Mass vs Sigmarelation at z=0.36
Woo, Treu, Malkan & Blandford 2006, astro-ph yesterday!
The Black-Hole Mass vs Sigmarelation 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 effects
2.Problems with the ECPI method
3.Evolution
Recent evolution of (active) bulges?
Treu et al. 2006b
Closing remarks:conjectures and predictions..
•Galaxies form initiallyas blue disks
•Major mergers 1) triggerAGN activity, 2) quenchstar formation, 3)increase the bulge size
•The characteristic massscale decreases withtime (‘downsizing’),consistent with that ofour galaxies at z=0.36
Hopkins et al. 2006
redshift
Log Mtr
The M-sigma relation should be already in place for larger masses!
The end