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

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 historyrecombination

Cosmic Dark Ages: no light no star, no quasar; IGM: HIFirst light: the first galaxies and quasars in the universeEpoch 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+04Giavalisco+04Bunker+04Bouwens+04Stavelli+04Mobasher+05Yan+06Bouwens+06Iye+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 deg2 at zAB<20 – 23 luminous quasars at

5.7<z<6.4

• Highest redshift: z=6.43, SDSS J1148+5251

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)

SDSS J1148+5251

1kpc

CO

Walter et al 04

Maiolino et al 05

CII

Fe

Barth et al 03

radio

Bertoldi et al 03

radio

Bertoldi et al 03Fan et al 03

optical

• 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)

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 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-simulationsParent 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 aYUV420 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.

• 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

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, 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…)

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. BHsstars BH

Y (

Mpc

/h)

Log

Ifra

c

X (Mpc/h) 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.• MCO~2x109M⊙, Mdyn~1012 M⊙, >> 5x1010 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 SDSSJ1148+5251 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

…