Download The formation and evolution of field early

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. 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 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
Log M>11.5
Young stars <1%
11.5>Log M>11
11>Log M
Young stars ~5% Young stars up to 20-40%
Treu et al. 2005b
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!
• 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
Black-Hole Mass. Empirically
Calibrated Photo-Ionization Method
L (5100AA)
Wandel Peterson & Malkan 1999; Kaspi et al. 2000
Kaspi et al. 2005
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!
Δlog M BH
The Black-Hole Mass vs Sigma
relation at z=0.36; cosmic evolution?
redshift
Δlog MBH = 0.62±0.10±0.25 dex
Conclusions.
• Bulges at z=0.36 smaller than their blackhole masses suggest. Three possibilities:
1. Selection effects
2. Problems with the ECPI method
3. Evolution
Recent evolution of (active) bulges?
Treu et al. 2006b
• 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
Closing remarks:
conjectures and predictions..
redshift
Hopkins et al. 2006
The M-sigma relation should be already in place for larger masses!
The end