Massive galaxies in massive datasets
M. Bernardi, J. Hyde and E. Tundo
University of Pennsylvania

Importance of Early-Type Galaxies
– Stellar masses & Black Holes
The Hierarchical formation picture
– Down-sizing and Dry mergers
Testing Dry mergers using scaling relations
– Luminosities, Sizes, Velocity dispersions, Colors
Selection bias in the M bh
– L – s relations

Early-types don’t dominate number, but they do dominate stellar mass
Renzini 2006
57%
43%
83%
17%

The most massive galaxies are red and dead

Connection with “AGN feedback”!!
Ferrarese & Merritt 2000 Gebhardt et al. 2000

Downsizing
Star formation only in smaller systems at late times
Environmental dependence important, but controversial
( Thomas et al.
2005; but see
Bernardi et al.
2006a; Bundy et al . 2006 )

Old stellar population (OK for everybody!!)
?? When were galaxies assembled ??
Population of massive red galaxies seen even at z~1.5 (K20 Survey, VVDS)
Consistent with passive evolution (e.g. Cimatti et al. 2006,
Bundy et al. 2006, Brown et al. 2006)
OR
Still assembling at low z (e.g. Faber et al. 2006)?
In the hierarchical formation picture …..
the problem is to form stars , and assemble them into a single massive system, in a relatively short time (in this respect, LCDM is friendlier than SCDM)
How to do this?

Importance of Early-Type Galaxies
– Stellar masses & Black Holes
The Hierarchical formation picture
– Down-sizing and Dry mergers
Testing Dry mergers using scaling relations
– Luminosities, Sizes, Velocity dispersions, Colors
Selection bias in the M bh
– L – s relations

New models match K-band luminosity function at z~0
Bower et al. 2006 (Durham)
Croton et al. 2006 (Munich)
Main change is to include AGN related effects
No AGN feedback
AGN feedback

Latest generation of semi-analytic models, calibrated to z=0, able to match K-band luminosity function at z~1.5
Main change is to include AGN related effects  BCG
Dry mergers common
Passive evolution
+ Dry mergers
Bower et al. 2006 (Durham)

Bimodality
Models now produce reasonable colormagnitude relations
BCGs bluer?
Croton et al. 2006 (Munich)
Satellite galaxies
(not BCGs)
BCGs
BCGs
Bower et al. 2006 (Durham)

Importance of Early-Type Galaxies
– Stellar masses & Black Holes
The Hierarchical formation picture
– Down-sizing and Dry mergers
Testing Dry mergers using scaling relations
– Luminosities, Sizes, Velocity dispersions, Colors
Selection bias in the Mbh – L – s relations

C4 cluster catalog
Uses both position and color info
Miller et al. 2005

Pairwise scaling relations
– Faber-Jackson: Ls
– Kormendy: I e
-R e
– L-R e
– Color - L
Inclusion of third parameter
– The Fundamental Plane: I e
-R e
s
Are they the same for BCGs????

BCGs show deviation from Kormendy relation
Oegerle & Hoessel 1991
BCGs
ETGs

Upturn to larger sizes at large luminosities
Oegerle & Hoessel 1991
R ~ L 0.8
R ~ L 0.6
Why?
Dry merging?
● BCGs
● Highs
Bernardi et al. 2007a

L-R relation expected to depend on mass ratio and impact parameter of merging spheroids
(Robertson et al. 2006)

s
Flattening?
● 2 comp
● deV
Scatter correlates with size: consistent with Virial theorem: s
2 ~ M/R

The Fundamental Plane

Bimodality
Models now produce reasonable colormagnitude relations
BCGs bluer?
Satellite galaxies
(not BCGs)
BCGs
Bower et al. 2006 (Durham)

BCGs
Croton et al. 2006 (Munich)
Bower et al. 2006 (Durham)

SDSS measurements OUR measurements
B03-Etypes
C4-BCGs
PL-BCGs

Models
OUR-SDSS
B03-Etypes
C4-BCGs
PL-BCGs
Hyde & Bernardi 2007

Another class of massive galaxies?
BCGs are most luminous galaxies
What about galaxies with largest s
:
– these host the most massive BHs
– constraints on formation mechanism
(cooling cutoff)
Once again, to select a clean sample must worry about systematics!

Galaxies with the largest velocity dispersion
● Single/Massive
 Double
◊ BCG
Sheth et al. 2003
Bernardi et al. 2006b
Expect 1/300 objects to be a superposition

‘Double’ from spectrum and image

‘Double’ from spectrum, not image

‘Single?’

SDSS J151741.7-004217.6
1’
3”
SDSS s
= 412 ± 27 km/s
HST

SDSS J204712.0-054336.7
1’
3’
SDSS s
= 404 ± 32 km/s
HST

s
= 369 ± 22 s
= 383 ± 27 s
= 385 ± 34 s
= 385 ± 24 s
= 395 ± 27 s
= 402 ± 35 s
= 404 ± 32 s
= 407 ± 27 s
= 408 ± 39 s
= 413 ± 35
HST: ACS-HRC
28 single 15 multiple
Large s not likely due to projection

Compared to
BCGs, large s sample has smaller sizes
Large s from extreme dissipation?
Oegerle & Hoessel 1991
L ~ R 0.8
L ~ R 0.6
● Highs
● BCGs
Bernardi et al. 2006b

Importance of Early-Type Galaxies
– Stellar masses & Black Holes
The Hierarchical formation picture
– Down-sizing and Dry mergers
Testing Dry mergers using scaling relations
– Luminosities, Sizes, Velocity dispersions, Colors
Selection bias in the M bh
– L – s relations

Selection bias in the M bh
- L s
!

Discrepancy between M bh function from L and s
From L
From s
Tundo et al. 2007

What is the cause for this discrepancy?
Selection bias in the s
-L relation!!
Bernardi et al. 2007b

Hierarchical models getting closer to observations … but not there yet
BCGs should be good testing ground
BCGs appear to be consistent with dry merger formation
Large s objects consistent with more dissipation
Selection bias in the M bh
– L s