The co-evolution of massive ellipticals

& their black holes

The co-evolution of massive ellipticals

& their black holesThorsten Naab

University Observatory, Munich

8th Sino-German Workshop on Galaxy Formation and Cosmology

Kunming, August 2008

M. Hirschmann, L. Oser, R. Jesseit, P. Johansson, C. Maulbetsch, J. Ostriker, A. Burkert, R. Somerville

• Recent observations indicate the existence of evolved, massive

(1011M), compact (r1/2 ≈ 1kpc) galaxies with very low star formation rates at z≈2 (e.g. van Dokkum et al. 2008, Cimatti et al. 2008 and

others)

• Systems are a factor three to five smaller than present day ellipticals of similar mass

• The stellar mass densities are more than one order of magnitude higher

• Simple passive evolution is in contradiction with stellar populations of local ellipticals (Kriek et al. 2008)

Compact massive ellipticals at z≈2Compact massive ellipticals at z≈2 Compact massive ellipticals at z≈2Compact massive ellipticals at z≈2

• Dry, gas-poor, red, collisionless… mergers are the prime

candidate, also with respect to the observed mass evolution in the red sequence (e.g. Brown et al. 2007, Faber et al. 2007)

• Additional presence of a dissipative component would limit the size evolution and add young stellar populations

• Compact ellipticals are already massive and from the shape of the mass function minor mergers are expected to be more common than major mergers

• There is theoretical (see e.g. Genel et al 2008) as well as direct observational evidence (see e.g. Bundy et al. 2009) that major mergers alone cannot account for the mass evolution of massive galaxies

Is this evolution driven by mergers? Is this evolution driven by mergers? Is this evolution driven by mergers? Is this evolution driven by mergers?

Minor mergers and the virial theorem Minor mergers and the virial theorem

Initial stellar system formed by e.g. dissipative collapse plusadded stellar material…

&

Minor mergers and the virial theorem Minor mergers and the virial theorem

Dispersion can decrease by factor 2

Naab, Johansson & Ostriker 2009

Mf = (1+)*Mi and assume =1, e.g. mass increase by factor two, and varying dispersions…

Radius can increase by factor 4

Density can decrease by factor 32

Naab, Johansson, Ostriker & Efstathiou 2007

The cosmological formation of an elliptical galaxyThe cosmological formation of an elliptical galaxy The cosmological formation of an elliptical galaxyThe cosmological formation of an elliptical galaxy

Stars

Blue: age < 1Gyr Yellow: 1Gyr < age < 5 Gyrs

Orange: age > 5 Gyrs

Simulations with GADGET2 (Springel, 2005)

Naab, Johansson, Ostriker in prep.

In-situ & accreted starsIn-situ & accreted starsIn-situ & accreted starsIn-situ & accreted stars

In-situ stars form a compact high density stellar system

Accreted stars are building up a more extended lower mass system – significant gravitational energy input from accreted stars (Johansson, Naab & Ostriker 2009 in prep.)

The two phases of ETG formation

The two phases of ETG formation

see e.g. Dekel, Ocvirk, Keres, Kravtsov, Brooks and more

Since z=2: 50% increase in mass-but factor of 3 in size without major mergers

1003 Mpc, 5123 particles dark matter only & with gas and simple star formation & feedback, 100 snapshots (WMAP3: Ωm = 0.26, Ω = 0.74, h = 0.72)

Re-simulation of a large number of individual halos from 1010-1013 (Mgas: 106, 105, 104) without gas, with star formation & evtl. feedback (Springel & Hernquist 2003)

Particular care to create efficient ICs and avoiding massive intruders: e.g. follow the virial region of target halos and resolve all interactions (Oser, Naab, Johansson et al. in prep)

Extracted merger histories of full box and individual halos (Hirschmann, Maulbetsch, Naab et al. in prep) also for detailed comparison with semi-analytical predictions (with R. Somerville)

Sneak preview on early type galaxies….

The Re-Sim project… The Re-Sim project…

New set of simulations including SNII feedback (Springel & Hernquist 2003)

Massive group galaxy:M*(<30kpc) = 4.5*1011

Lower mass galaxies;M*(<30kpc) = 2.3*1011

Differential size growth: minor vs. major mergers -> Luminosity function

Still have to establish the direct connection between size growth and merger history – work in progress

The rapid size evolution of spheroids The rapid size evolution of spheroids

Slow and fast rotating ETGs from observationsSlow and fast rotating ETGs from observations

From 48 Sauron galaxies to 265 ATLAS3D galaxies

Most massive ETGs are slowly rotating, triaxial, misalignedand round: How do they form?

Cappellari et al. 2007, 2008 in prep.

Slow and fast rotating ETGs from cosmo-simsSlow and fast rotating ETGs from cosmo-sims

The R parameter(Emsellem et al. 2007)

Fast rotator: R > 0.1

Naab, Jesseit et al. ; Jesseit, Naab et al. in prep.

Baryons locked in starsBaryons locked in stars

Good slope (heating) but central galaxies are about factor 2 too massive!

AGN feedback? Stellar mass loss? Star formation driven winds?

Comparison to SAMsComparison to SAMs

Create high-resolution merger trees of resimulatedf halos and with SAMs for direct comparison (with R. Somerville)

• Schwarzschild & Jeans modeling of early-type galaxies (Tortora et al. 2009, Thomas et al. 2009)

• More massive ellipticals have lower central dark matter densities

• Good agreement with Cold Dark Matter predictions (e.g. de Lucia & Blaziot 2007)

Dark matter in elliptical galaxiesDark matter in elliptical galaxies

Simulated galaxies have a stellar mass–dark matter density relationsimilar to observed ellipticals

Significantly more contraction in lower mass halos due to accretionand cooling

Dark matter in elliptical galaxiesDark matter in elliptical galaxies

Jesseit, Naab et al. 2009 in prep.

Simulated galaxies have a stellar mass–dark matter density relationsimilar to observed ellipticals

Significantly more contraction in lower mass halos due to accretionand cooling

Dark matter in elliptical galaxiesDark matter in elliptical galaxies

Jesseit, Naab et al. 2009 in prep.

Johansson, Naab, Ostriker et al. 2009 in prep.

• Do many more cases at high resolution• Look at detailed evolutionary history and its

connection to galaxy properties• Look at X-ray properties• Add recycled gas (with Dave & Oppenheimer)

• Include metallicity evolution• Better gas cooling physics • Look at gravitational lensing properties.• Repeat with better feedback• Add recycled gas• Add central QSO• Learn from SAMs?

To be done…To be done…

Fraction of Mvir to stellar mass in central galaxy ---> function of galaxy mass (again)Mandelbaum et al. 2007 find 30 (lensing)

Slow and fast rotating ETGs from disk mergersSlow and fast rotating ETGs from disk mergers

Statistical set of 1;1 and 3:1mergers with SF & Feedback (Naab et al. in prep, Jesseit et al. 2008)

For a full 2D kinematical ‘kinemetry’ analysis see Jesseit et al. 2007 MNRAS, 376, 997

The R parameter(Emsellem et al. 2007)

Fast rotator: R > 0.1

Lambda & binary mergersLambda & binary mergers

In the idealized world: mass ratio is the decisive factor for slow/fast rotatorsBasically all re-mergers make slow rotators

Rotation in merger remnants Rotation in merger remnants

Fast and slow rotators defined from 2D kinematical analysis

Challenges for major mergers: Missing metals Challenges for major mergers: Missing metals Challenges for major mergers: Missing metals Challenges for major mergers: Missing metals

•Typcial ellipticals are more metal rich than typical present day disks and their progenitors•Ellipticals have older stellar populations that formed on smaller timescales (e.g. Thomas et al.)

•Massive ellipticals can not typically have formed from binary mergers of present day disks and their progenitors•They might have formed at high z from disks whose descendents no longer exist (Naab & Ostriker 2008)

Binary mergers of any kind are not isotropic; massive ETGs are!(Burkert, Naab & Johansson 2007)

Challenges for major mergers: Internal Kinematics Challenges for major mergers: Internal Kinematics Challenges for major mergers: Internal Kinematics Challenges for major mergers: Internal Kinematics

•3:1 remnants are anisotropic, despite (v/s)* > 0.7 •Disk merger remnants in general are more anisotropic and more elliptical than ‘real’ model ellipticals•Re-merging disk merger remnants does not solve this problem•Neither does star formation, feedback from SN and/or BHs•Cosmologically formed objects are round and slowly rotating

Burkert & Naab 2005; Burkert, Naab, Johansson & Jesseit 2008

Modelled data from Capellari et al. 2007, see Binney 2005

Stellar system in a low mass field halo Stellar system in a low mass field halo

Fast rotator: lambda = 0.3

Stellar system in a group halo Stellar system in a group halo

The two phases of ETG formation

The two phases of ETG formation

see e.g. Dekel, Ocvirk, Keres, Kravtsov, Brooks and more

Early dissipation vs. late accretionof stars

A protodisk at z = 2?A protodisk at z = 2? A protodisk at z = 2?A protodisk at z = 2?

0.5

v(Hα) (km/s)

vc = 230 km s-1

r1/e 4.5 kpcvc/σ 3

gas ~ 350 M pc–2

Mdyn 1.1 1011 M

M 0.8 1011 M

Mgas 0.4 1011 M

~ gas ~ 500 MyrSFR ~ 150 M yr–1

SFR ~ 1 M yr–1 kpc–2

BzK–15504 at z 2.38

Large, massive, gas-rich disk

Converting rapidlya significant fraction ofits baryonic mass into stars

No obvious evidence of major merger

Genzel et al. (2006)

The two phases of ETG formation The two phases of ETG formation

•Early phase of dissipative & collisionless collapse (6 > z > 2) driven by massive cold gas flows

•Formation of a small massive, metal enriched, proto-galactic core by in-situ star formation

•Similar for all ETGs -> homogenous stellar populations

•Later phase of mainly stellar accretion/mergers (3 > z > 0)

•Accretion of old, metal poor stars from smaller systems at larger radii

•Increase in mass & size, metallicity gradients, kinematics etc.

Large clumpy gas disks by mergers of large disks?Large clumpy gas disks by mergers of large disks?

Robertson & Bullock 2008

How do the 99% gas rich progenitordisks form?

Their star formation is strongly suppressed

Strong feedback leads to very smooth disks which aretypically not observed

No strong off-center star formation

Very short lifetimes of about 108

years - obs: about 109 years

Bulge formation during the mergerin contrast with a fraction ofobserved galaxies (e.g. BX 482) (Genzel et al. 2008)

Outlook: the near future ‘at least’ in galaxy formation Outlook: the near future ‘at least’ in galaxy formation Outlook: the near future ‘at least’ in galaxy formation Outlook: the near future ‘at least’ in galaxy formation

•Understanding galaxy formation from re-simulated

individual halos in a full cosmological context

•Constraining uncertainties due to limitations of numerical methods

•Baryon inflow, star formation, winds and metal enrichment in massive galaxies at z=2-4

•Formation of galaxy groups and clusters which are the ‘real’ hosts of massive galaxies

Large clumpy gas disks by disk instabilities?Large clumpy gas disks by disk instabilities?

Cosmologically motivated 1012 solar mass halo at z=22kpc stellar disk and flat gas disk with 120 M/pc2

Gas fraction: 70%

See Noguchi et al. 1999, Immeli et al. 2004,Bournaud et al. 2007, Elmegreen et al. 2008

Short to intermediate lifetimes

Fragmentation only with low feedback efficiencies

Low velocity dispersions

Does not explain bulges with highSFR

Turbulent star forming disks at z=2-3Turbulent star forming disks at z=2-3 Turbulent star forming disks at z=2-3Turbulent star forming disks at z=2-3

403 particles : Mgas= 3.2 x 107 , = 0.6 kpc 503 particles : Mgas= 1.6 x 107 , = 0.5 kpc 1003 particles : Mgas= 2.1 x 106 , = 0.25 kpc 2003 particles : Mgas= 2.6 x 105 , = 0.13 kpc

At higher resolution star formation is more extended; environment is more turbulent; star formation rate is higher (30 solar masses/year)

8 x 1010 stellar spheroid & 1 x 1010 cold gas

High velocity dispersion: v/= 3

Long lifetimes of order 109 Gyrs due to continuous clumpy gas supply

Too low gas fractions/SFRs

Significant bulge

Mock galaxy at z=2.38Mock galaxy at z=2.38 Mock galaxy at z=2.38Mock galaxy at z=2.38

Velocity fields Dispersion mapsLine maps

16.8 kpc x 16.8 kpc – SINFONI 100mas, PSF FWHM=0.15, 75km/s, 6h

Naab, Foerster-Schreiber et al. 2008

• Egrav~m* unlike ESN and EAGN which are both proportional to m*. Egrav dominates for massive galaxies with high

• The cumulative change in binding energy for insitu and accreted stars. At z<1 haloes A,C accrete mass (dissipationless), halo E dominated by insitu (dissipational).

• At high z, high fraction of cool star-forming gas.

• Shock-heating of the diffuse gas dominates at all redshifts, but especially at z<3, when the galaxies are massive enough to support stable shocks.

• More massive haloes (A) show larger heating rates compared to C and E.

Supernova II feedback:

AGN feedback:

Gravitational feedback:

Simple feedback energeticsSimple feedback energeticsSimple feedback energetics Simple feedback energeticsSimple feedback energetics

• Egrav~m* unlike ESN and EAGN which are both proportional to m*. Egrav dominates for massive galaxies with high

• The cumulative change in binding energy for insitu and accreted stars. At z<1 haloes A,C accrete mass (dissipationless), halo E dominated by insitu (dissipational).

Evolution of the central densities… Evolution of the central densities…

High resolution re-simulation with 1.6*107 particles, mgas= 2.6*105, = 0.13 kpc.

Dark matter density firstincreases and then decreases again.