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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/0608190), 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 supermassive 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 • z>4: >1000 known • z>5: >60 • z>6: 13 (12 SDSS discoveries) • SDSS i-dropout Survey: – 7000 deg2 at zAB<20 – 23 luminous quasars at 5.7<z<6.4 • Highest redshift: z=6.43, SDSS J1148+5251 Fan et al 03, 06 Quasars at z~6 • • • • End of reionization Bright, Lbol ~ 1013-14 L⊙ Rare, ~1 Gpc-3 Massive, MBH~109 M⊙,Mhalo ~ 1013 M⊙ (Becker+01, White03, Fan+04) CO SDSS J1148+5251 optical radio radio Walter et al 04 1kpc Fan et al 03 • • • • • • • Bertoldi et al 03 Bertoldi et al 03 Lbol ~1014 L⊙ (Barth+03) MBH ~3x109 M⊙ (Willot+03) LFIR ~1013 L⊙ (Carilli+04) SFR ~103 M⊙/yr (Bertoldi+03) MCO ~5x109 M⊙ (Walter+04) Mdust ~7x108 M⊙ (Beelen+06) Heavy metal enrichment (Barth+03,Maiolino+05,Becker+06) CII Maiolino et al 05 Fe Barth et al 03 Challenges • Can such massive objects form so early in the LCDM cosmology? • How do BHs grow? At constant or superEddington 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 clusterscaling 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 Gpc3 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-1Mpc, 4003 WMAP1 WMAP3 Zoom-in re-simulations Parent sim: 1000 h-1Mpc, 4003 Zoom: HR-region ~60 h-1Mpc, 4003 Merger tree of quasar halo • FoF is employed to construct the merging history of the quasar halo • Merger tree of the halo 7.7x1012 M⊙ at z~6 is then followed with hydrodynamical resimulation with real galaxies A vigorous merging history QuickTime™ and a YUV420 codec decompressor are needed to see this picture. 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. Starburst progenitors • SFR varies highly, mean ~ 103 M⊙/yr, peak ~104 M⊙/yr at z~9, drops to ~100 M⊙/yr at z~6.5 • Observational estimate ~103 M⊙/yr at z~6.4 assuming LFIR dominated by young stars --> AGN contamination Early metal enrichment • Metal enrichment starts at z>14 • Become supersolar 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 superEddington accretion not neccessary Redshift z Correlation btw BH & galaxies • At z~6.5 peak of quasar phase, Mbh ~ 2x109 M⊙ , M* ~ 1012 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…) Age of Universe (Gyr) 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 & Fan+03 Scoville88, Sanders88) Redshift z IR Calculations rest (m) Evolution of SEDs Cold ULIRG --> warm ULIRG (Sanders+96) rest (m) HII regions from stars vs. BHs BH Log Ifrac Y (Mpc/h) stars X (Mpc/h) X (Mpc/h) CO excitation & morphology Narayanan+06 • 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. • MCO~2x109M⊙, Mdyn~1012 M⊙, >> 5x1010 M⊙ estimated (Walter et al 04). BH & stellar bulge form coevally Summary • Our model simultaneously accounts for BHs growth, quasar activity & host galaxy properties, successfully reproduces the observed properties of SDSSJ1148+5251 in the LCDM cosmology. – Both BHs and host galaxies build up through hierarchical mergers. – BHs accrete gas under Eddington limit in a selfregulated 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 …