The co-evolution of massive ellipticals & their black holes Thorsten Naab University Observatory, Munich 8 th 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 (10 11 M  ), compact (r 1/2 ≈ 1kpc) galaxies with very low star formation rates at z≈2 (e.g. van Dokkum et al. 2008, Cimatti et al 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≈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?

Minor mergers and the virial theorem Initial stellar system formed by e.g. dissipative collapse plus added stellar material… &

Minor mergers and the virial theorem Dispersion can decrease by factor 2 Naab, Johansson & Ostriker 2009 M f = (1+  )*M i 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 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 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 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

100 3 Mpc, particles dark matter only & with gas and simple star formation & feedback, 100 snapshots (WMAP3: Ω m = 0.26, Ω  = 0.74, h = 0.72) Re-simulation of a large number of individual halos from (M gas : 10 6, 10 5, 10 4 ) 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…

New set of simulations including SNII feedback (Springel & Hernquist 2003) Massive group galaxy: M * (<30kpc) = 4.5*10 11 Lower mass galaxies; M * (<30kpc) = 2.3*10 11 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

Slow and fast rotating ETGs from observations From 48 Sauron galaxies to 265 ATLAS 3D galaxies Most massive ETGs are slowly rotating, triaxial, misaligned and round: How do they form? Cappellari et al. 2007, 2008 in prep.

Slow 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 stars Good slope (heating) but central galaxies are about factor 2 too massive! AGN feedback? Stellar mass loss? Star formation driven winds?

Comparison 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 galaxies

Simulated galaxies have a stellar mass–dark matter density relation similar to observed ellipticals Significantly more contraction in lower mass halos due to accretion and cooling Dark matter in elliptical galaxies Jesseit, Naab et al in prep.

Simulated galaxies have a stellar mass–dark matter density relation similar to observed ellipticals Significantly more contraction in lower mass halos due to accretion and cooling Dark matter in elliptical galaxies Jesseit, Naab et al in prep. Johansson, Naab, Ostriker et al 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…

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

Slow 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 MNRAS, 376, 997 The R parameter (Emsellem et al. 2007) Fast rotator: R > 0.1

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

Rotation in merger remnants Fast and slow rotators defined from 2D kinematical analysis

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 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 Fast rotator: lambda = 0.3

Stellar system in a group halo

The two phases of ETG formation see e.g. Dekel, Ocvirk, Keres, Kravtsov, Brooks and more Early dissipation vs. late accretion of stars

A protodisk at z = 2? 0.5  v(Hα) (km/s)  v c = 230 km s -1  r 1/e  4.5 kpc  v c /σ  3   gas ~ 350 M  pc –2  M dyn  1.1  M   M   0.8  M   M gas  0.4  M     ~  gas ~ 500 Myr  SFR ~ 150 M  yr –1   SFR ~ 1 M  yr –1 kpc –2 BzK–15504 at z  2.38  Large, massive, gas-rich disk  Converting rapidly a significant fraction of its baryonic mass into stars  No obvious evidence of major merger Genzel et al. (2006)

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? Robertson & Bullock 2008 How do the 99% gas rich progenitor disks form? Their star formation is strongly suppressed Strong feedback leads to very smooth disks which are typically not observed No strong off-center star formation Very short lifetimes of about 10 8 years - obs: about 10 9 years Bulge formation during the merger in contrast with a fraction of observed galaxies (e.g. BX 482) (Genzel et al. 2008)

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?  Cosmologically motivated solar mass halo at z=2  2kpc stellar disk and flat gas disk with 120 M/pc 2  Gas fraction: 70% See Noguchi et al. 1999, Immeli et al. 2004, Bournaud et al. 2007, Elmegreen et al Short to intermediate lifetimes Fragmentation only with low feedback efficiencies Low velocity dispersions Does not explain bulges with high SFR

Turbulent star forming disks at z= particles : M gas = 3.2 x 10 7,  = 0.6 kpc 50 3 particles : M gas = 1.6 x 10 7,  = 0.5 kpc100 3 particles : M gas = 2.1 x 10 6,  = 0.25 kpc particles : M gas = 2.6 x 10 5,  = 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 stellar spheroid & 1 x cold gas

High velocity dispersion: v/  = 3 Long lifetimes of order 10 9 Gyrs due to continuous clumpy gas supply Too low gas fractions/SFRs Significant bulge Mock 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

E grav ~m *   unlike E SN and E AGN which are both proportional to m *. E grav 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 energetics

E grav ~m *   unlike E SN and E AGN which are both proportional to m *. E grav 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… High resolution re-simulation with 1.6*10 7 particles, m gas = 2.6*10 5,  = 0.13 kpc. Dark matter density first increases and then decreases again.