Formation & evolution of galaxies and quasars at z~6 Yuexing Li Harvard / CfA

Collaborators CfA: Lars Hernquist, T.J. Cox, Phil Hopkins, Matt McQuinn, Giovanni Fazzio, Doug Finkbeiner, Matias Zaldarriaga Tiziana DiMatteo (UCM), Liang Gao, Adrian Jenkins (Durham), Brant Robertson, Andrew Zentner (Chicago), Volker Springel (MPA), Naoki Yoshida (Nagoya) Arizona: Xiaohui Fan, Linhua Jiang, Desika Narayanan References Li, Hernquist et al. (2006A, astro-ph/ ), Formation Li, Hernquist et al. (2006B, in preparation), IR properties Li, McQuinn et al. (2006C, in preparation), HII regions Narayanan, Li et al. (2006, ApJ submitted), CO emission

A brief cosmic history  recombination  Cosmic Dark Ages: no light no star, no quasar; IGM: HI  First light: the first galaxies and quasars in the universe  Epoch of reionization: radiation from the first object lit up and ionize IGM : HI  HII  reionization completed, the universe is transparent and the dark ages ended today Courtesy: X. Fan, G. Djorgovski

High-z galaxies & quasars as cosmology probes First generation of galaxies and quasars Star formation and metal enrichment in the early universe Formation and growth of early super- massive black holes Role of quasars /BH feedback in galaxy evolution Epoch of reionization

An exiciting hi-z Universe thanks to HST, Spitzer, Sloan… Ferguson+00 Dickinson+04 Giavalisco+04 Bunker+04 Bouwens+04 Stavelli+04 Mobasher+05 Yan+06 Bouwens+06 Iye+06 …. Fan+01,03,04,06 …

A census of high-z quasars Fan et al 03, 06 z>4: >1000 known z>5: >60 z>6: 13 (12 SDSS discoveries) SDSS i-dropout Survey: –7000 deg 2 at z AB <20 –23 luminous quasars at 5.7<z<6.4 Highest redshift: z=6.43, SDSS J

Quasars at z~6 End of reionization Bright, L bol ~ L ⊙ Rare, ~1 Gpc -3 Massive, M BH ~10 9 M ⊙,M halo ~ M ⊙ (Becker+01, White03, Fan+04)

SDSS J kpc CO Walter et al 04 Maiolino et al 05 CII Fe Barth et al 03 radio Bertoldi et al 03 radio Bertoldi et al 03 Fan et al 03 optical L bol ~10 14 L ⊙ (Barth+03) M BH ~3x10 9 M ⊙ (Willot+03) L FIR ~10 13 L ⊙ (Carilli+04) SFR ~10 3 M ⊙ /yr (Bertoldi+03) M CO ~5x10 9 M ⊙ (Walter+04) M dust ~7x10 8 M ⊙ (Beelen+06) Heavy metal enrichment (Barth+03,Maiolino+05,Becker+06)

Challenges Can such massive objects form so early in the LCDM cosmology? How do BHs grow? At constant or super- Eddington accretion rate? Where does the quasar halo originate? What are the initial conditions? What is the nature of the progenitors? Do they grow /evolve coevally with SMBHs? How does BH feedback affect the hosts? What are the reionization sources?

Formation of galaxies & QSOs Account for BH growth, quasar activity and host galaxy properties Galaxy formation and growth in hierarchical cosmology BH growth in context of galaxy formation Context of large-scale structure formation & galactic-scale gasdynamics, SF, BH growth, feedback

Close link between galaxy formation & BH growth Observations: –M-  correaltion –Similarity btw cosmic SFH & quasar evolution Theorectical models BH growth is regulated by feedback (Silk & Rees98, Wyithe & Loeb03, TiMatteo et al 05) –Blow out of gas once BH reachs critical mass BHs may play important roles in galaxy formation Feeback by AGN may - –Solve the cooling flow riddle in galaxy clusters –Explain the cluster- scaling relations –Explain why ellipticals are so gas-poor & red –Metal enrichment of IGM by quasar-driven winds –Help to reionize and surpress star formation in small galaxies

Our approach Multi-scale simulations with GADGET2 (Springel 06) –N-body cosmological simulation in 3 Gpc 3 –Largest halo at z=0 identified –Resimulate the halo region with zoom-in –Merging history prior to z=6 extracted –Resimulate the merger tree with real galaxies scaled appropriately with z Self-regulated BH growth model (DiMatteo et al. 05) –Bondi accretion under Eddington limit –Feedback by BHs in thermal energy coupled to gas

Cosmological Simulations Parent sim: 1000 h -1 Mpc, WMAP1 WMAP3

Zoom-in re-simulations Parent sim: 1000 h -1 Mpc, Zoom: HR-region ~60 h -1 Mpc, 400 3

Merger tree of quasar halo FoF is employed to construct the merging history of the quasar halo Merger tree of the halo 7.7x10 12 M ⊙ at z~6 is then followed with hydrodynamical resimulation with real galaxies

A vigorous merging history

Evolution of quasar host Early on -- galaxies interact violently, blue, starbursting -- quasar is heavily obscured. When galaxies coalesce -- accretion peaks -- quasar becomes optically visible as feedback blows out gas. Later times -- SF & AR quenched, --> reddened & aging spheroid.

SFR varies highly, mean ~ 10 3 M ⊙ /yr, peak ~10 4 M ⊙ /yr at z~9, drops to ~100 M ⊙ /yr at z~6.5 Observational estimate ~10 3 M ⊙ /yr at z~6.4 assuming L FIR dominated by young stars --> AGN contamination Starburst progenitors

Early metal enrichment Metal enrichment starts at z>14 Become super- solar at z~12 Consistent with metallicity derived from CO ( Walter et al 03 ), Fe emission ( Barth et al 03 ) & CII line ( Maiolino et al 05 ) observations.

BH growth AR peaks at z~6.5 when galaxies coalesce. AR varies highly depends on strength of interaction & feedback. Only a portion of lifetime accretes at Eddington rate --> constant or super- Eddington accretion not neccessary Redshift z

Correlation btw BH & galaxies At z~6.5 peak of quasar phase, M bh ~ 2x10 9 M ⊙, M * ~ M ⊙  Magorrian relation  Coeval growth of BH & stellar spheroid through mergers  Time-independent, only depend on formation of galaxy & BH and feedback Ambiguous inferences from observations (Walter+04, Peng+06, Shields+06…)

Quasar lightcurves System is intrinsic bright as ULIRG Starburst dominates before quasar phase At z~6.5, quasar light dominates --> phase transition from starburst to quasar (Norman & Scoville88, Sanders88) Age of Universe (Gyr) Redshift z Fan+03

IR Calculations rest (  m)

Evolution of SEDs rest (  m) Cold ULIRG --> warm ULIRG (Sanders+96)

HII regions from stars vs. BHs starsBH Y (Mpc/h) Log Ifrac X (Mpc/h)

CO excitation & morphology CO (J=6-5) excitation reproduces Bertoldi et al 03. CO (J=3-2) morphology agree with Walter et al 03, show multiple peaks --> merger origin CO emission shows multiple components ~300 km/s as observed, FWHM ~ 1500 km/s --> a broader line likely unresolved in obs. M CO ~2x10 9 M ⊙, M dyn ~10 12 M ⊙, >> 5x10 10 M ⊙ estimated (Walter et al 04).  BH & stellar bulge form coevally Narayanan+06

Summary Our model simultaneously accounts for BHs growth, quasar activity & host galaxy properties, successfully reproduces the observed properties of SDSSJ in the LCDM cosmology. –Both BHs and host galaxies build up through hierarchical mergers. –BHs accrete gas under Eddington limit in a self- regulated manner owing to feedback. Our model should provide a viable mechanism for other luminous quasars, no exotic process is needed.

Predictions The quasar host obeys the Magorrian relation. The system evolves from cold ULIRG -- > warm ULIRG as quasar grow stronger Quasar progenitors are strong starburst galaxies, providing important contribution to metal enrichment, and reionization.

On-going & future work Can we see them? –Detectability of these high-z QSOs & galaxies How many are there? – Abundance, luminosity function & clustering of these objects at z>6 What are the sources for reionization? –Contributions from quasars & galaxies …