Galaxies and Quasars in the Epoch of Reionization

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Galaxies and Quasars in the Epoch of Reionization

• Yuexing Li
• Keck Fellow
• Harvard-CfA

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Main Collaborators

• Thoeretical Lars Hernquist (CfA),
  Volker Springel (MPA),
  Tiziana Di Matteo (CMU), Tom Abel
  (Stanford)
• Observational Giovanni Fazio (CfA),
  Xiaohui Fan (Arizona)

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Cosmic Hisotry

• 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
  objects lit up and ionize IGM HI ? HII

? reionization completed, the universe is
transparent and the dark ages ended
today
Courtesy George Djorgovski
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Exciting Era for High-z Objects
Fan01,03,04,06 Schneider03,05,07 Willott07
. Giavalisco04 Bouwens06, 07 Thompson05,
06 Iye06, Yan06 . Brandt02 Shemmer06
Bertoldi03, Carilli04 Beelen06,
Jiang06 Maiolino04, Wang07 Schady08
Fynbo08
Presence of large stellar component in galaxies,
Mstar gt 1011 M? at zgt6
Presence of SMBH in quasars, MBH109 M?
Presence of copious dust Mdust108 M? in these
objects
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Questions Myths

• I Can such massive objects form so early in the
  LCDM cosmology?
• myth there is a cut-off at z5 (Efstathiou
  Rees 88)
• myth exotic mechanisms required, e.g.,
  super-Eddington accretion (Volonteri Rees 05,
  06) supermassive BH seeds (Bromm Loeb 03,
  Haiman 04, Dijstra08)
• II How do they grow and evolve?
• myth z6 quasars have undersized host galaxies
  (Walter2003)
• myth SMBH host correlations dont hold at high
  z
• III What are their contributions to IR emission
  and reionization?
• myth all FIR comes from star heating
  (Bertoldi2003, Carilli2004)
• myth quasars dont contribute to reionization
  (e.g., Gnedin04)

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Modeling Galaxies QSOs

• Physics to account for close link between galaxy
  formation and BH growth
• SMBH - host correlations (e.g, Magorrian98,
  Gebhardt00, Ferrarese00, Tremaine02)
• Similarity between cosmic SFH quasar evolution
  (e.g., Madau95, Shaver96)
• Hydrodynamic simulations to follow evolution of
  quasar activity and host galaxy
• Large-scale structure formation
• Galactic-scale gasdynamics, SF, BH growth
• Feedback from both stars and BHs
• Radiative transfer calculations to track
  interaction between photons and ISM /IGM
• Radiation from stars BHs
• Scattering, extinction of ISM reemission by
  dust
• Evolution of SEDs, colors, luminosities, AGN
  contamination

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GADGET2 (Springel 05)ART2 (Li et al
08A)(All-wavelength Radiative Transfer with
Adaptive Refinement Tree)
CARTCosmological All-wavelength Radiative
Transfer
Formation, evolution multi-band properties of
galaxies quasars
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I Quasar Formation - MIM

• Multi-scale simulations with GADGET2 (Springel
  05)
• N-body cosmological simulation in 3 Gpc3
• Identify halos of interest at z0
• Zoom in re-simulate the halo region with higher
  res.
• Merging history extracted
• Re-simulate the merger tree hydrodynamically
• Self-regulated BH growth model (DiMatteo et al.
  05)
• Bondi accretion under Eddington limit
• Feedback by BHs in thermal energy coupled to gas

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Formation of a z6 QSO from Hierarchical Mergers

• Merger tree with 7 major mergers z14-7
• Idealized galaxy using MMW model with properties
  (Mvir, Rvir, Cvir) scaled with z (Mo98)
• BH seeds from remnants of PopIII stars (Abel02,
  Bromm Larson04, Yoshida06, 08), M200 M? at
  z30
• BH binary merge when separation below resolution
• At high-z, the potential well is deeper because
  galaxies are more compact
• BH binary merge rapidly in gaseous environment
  (Escala04,05)
• Gravitational recoil may eject BH if Vkick gt
  Vesc, Vkick 100 475 km/s (e.g., Gonzalez07,
  Campanelli07)
• Maximum Vkick lt 200 km/s in gas-rich galaxy
  mergers (Bogdanovic07)
• Our halos have Vesc gt 300 km/s

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Co-evolution of SMBHs and Host
Age of Universe (Gyr)

• ltSFRgt 103 M?/yr, at zgt8, drops to 100 M?/yr at
  z6.5 ? heavy metal enrichment at zgt10
• Indiv. BH grows via gas accretion, total system
  grows collectively
• System evolves from starburst ? quasar
• Merger remnant MBH 2109 M? , M 1012 M? ?
  Magorrian relation

Redshift z
Li et al 07
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II Multi-band Properties - ART2

• 3-D Monte Carlo RT code ART2 treats radiative
  equilibrium ? calculate dust emission
  self-consistently (Bjorkman Wood 01)
• Adaptive grid (Jonsson06) ? cover large dynamical
  range, capture inhomogeneous density distribution
• Multi-phase ISM model (McKee Ostriker 77) GMC
  scaling relations (Larson 1981)
• Supernova-origin dust model ? dust in young,
  high-z objects (e.g., Maiolino04, Todini
  Ferrara 01)

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Evolution of SEDs
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Origin of Thermal Emission

• Quasar system evolves from cold --gt warm
• In peak quasar phase, radiation /heating is
  dominated by AGN
• Starbusts and quasars have different
  IR-optical-Xray correlations

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III. Galaxies Quasars in Cosmological Volume

• SPH cosmological simulations with BHs
• They form in massive halos in overdense regions
• They are highly clustered
• May provide patchy ionization of HI
• SMBH -- host correlations hold

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Summary

• CART is a powerful approach to study the
  formation, evolution, and multi-band properties
  of galaxies and quasars.
• Luminous z6 quasars can form in the LCDM
  cosmology ? hierarchical mergers of gas-rich
  proto-galaxies, with BH accretion under Eddington
  limit.
• Galaxy progenitors of these quasars are strong
  starbursts, providing important contribution to
  metal enrichment dust production.
• Early galaxies and quasars form in highly
  overdense region, highly clustered ? patchy
  reionization

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Predictions Observational Tests

• Birth place massive halos in overdense region
• Clustering, cross correlations of galaxies and
  quasars
• Lensing
• Triggering mechanism hierarchical merger
• Morphology, pairs, CO maps
• MBH -- ? relation
• Merger rate
• Evolutionary path Starburst --gt quasar
• Star formation history, evolved stellar
  components, mass functions
• Metal enrichment, molecular gas, dust
• Thermal emission stars --gt AGN
• SFR indicators
• IR - optical relations
• End product SMBH -- host correlations
• MBH -- Mhost relation