Galaxies and Quasars in the Epoch of Reionization Yuexing Li Keck Fellow Harvard-CfA.
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Transcript of Galaxies and Quasars in the Epoch of Reionization Yuexing Li Keck Fellow Harvard-CfA.
Galaxies and Quasars in the Epoch of Reionization
Yuexing LiKeck Fellow
Harvard-CfA
Main Collaborators
• Thoeretical: Lars Hernquist (CfA), Volker Springel (MPA),
Tiziana Di Matteo (CMU), Tom Abel (Stanford)
• Observational: Giovanni Fazio (CfA), Xiaohui Fan (Arizona)
Cosmic Hisotryrecombination
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 objects lit up and ionize IGM : HI HII reionization completed, the universe is transparent and the dark ages ended
today
Courtesy: George Djorgovski
Fan+01,03,04,06Schneider+03,05,07Willott+07 ….Giavalisco+04Bouwens+06, 07Thompson+05, 06Iye+06, Yan+06 ….Brandt+02Shemmer+06 Bertoldi+03, Carilli+04Beelen+06, Jiang+06Maiolino+04, Wang+07 …Schady+08 Fynbo+08 …
Courtesy: Edo Berger
HSTChandraSpitzerSDSSSubaruSWIFTGLASTMAMBO….
Exciting Era for High-z Objects
Presence of SMBH in quasars, MBH~109 M⊙
Presence of large stellar component in galaxies, Mstar > 1011 M ⊙ at z>6
Presence of copious dust Mdust~108 M⊙ in
these objects
Questions & MythsI: Can such massive objects form so early in the
LCDM cosmology?– myth: there is a “cut-off” at z~5 (Efstathiou & Rees 88)– myth: exotic mechanisms required, e.g., super-Eddington accretion
(Volonteri & Rees 05, 06); supermassive BH seeds (Bromm & Loeb 03, Haiman 04, Dijstra+08)
II: How do they grow and evolve?– myth: z~6 quasars have “undersized” host galaxies (Walter+2003)– myth: SMBH – host correlations don’t hold at high z
III: What are their contributions to IR emission and reionization?– myth: all FIR comes from star heating (Bertoldi+2003, Carilli+2004)– myth: quasars don’t contribute to reionization (e.g., Gnedin+04)
Modeling Galaxies & QSOs• Physics to account for close link between galaxy formation
and BH growth– SMBH - host correlations (e.g, Magorrian+98, Gebhardt+00,
Ferrarese+00, Tremaine+02…)– Similarity between cosmic SFH & quasar evolution (e.g., Madau+95,
Shaver+96)
• 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
GADGET2 (Springel 05)
+ART2
(Li et al 08A)
(All-wavelength Radiative Transfer with Adaptive Refinement Tree)
Formation, evolution & multi-band properties of galaxies & quasars
CARTCosmological All-wavelength Radiative Transfer
• Multi-scale simulations with GADGET2 (Springel 05)
– N-body cosmological simulation in 3 Gpc3
– Identify halos of interest at z=0– 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
I: Quasar Formation - MIMZoom: HR-region ~60 h-1Mpc, 4003
X (h-1 Mpc)
Y (
h-1
Mp
c)
Zoom-in sims
• Merger tree with 7 major mergers z~14-7• Idealized galaxy using MMW model with properties (Mvir,
Rvir, Cvir) scaled with z (Mo+98)• BH seeds from remnants of PopIII stars (Abel+02, Bromm
& Larson04, Yoshida+06, 08), M=200 M ⊙ at z=30• 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 (Escala+04,05)– Gravitational recoil may eject BH if Vkick > Vesc, Vkick ~100 – 475 km/s
(e.g., Gonzalez+07, Campanelli+07)– Maximum Vkick < 200 km/s in gas-rich galaxy mergers (Bogdanovic+07)– Our halos have Vesc > 300 km/s
Formation of a z~6 QSO from Hierarchical Mergers
G1G2
G3
G4
G5
G6G7 G8
7.7x1012 M⊙
Age of Universe (Gyr)
Redshift z
• <SFR> ~ 103 M⊙/yr, at z>8, drops to ~100 M⊙/yr at z~6.5 heavy metal enrichment at z>10
• Indiv. BH grows via gas accretion, total system grows collectively
• System evolves from starburst quasar
• Merger remnant MBH ~ 2*109 M⊙ , M* ~ 1012 M ⊙ Magorrian relation
Li et al 07
Co-evolution of SMBHs and Host
• 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., Maiolino+04, Todini & Ferrara 01)
II: Multi-band Properties - ART2
rest (m)
Opa
city
(cm
2 /g)
X (kpc)
Y (
kpc)
Evolution of SEDs
obs (m)Li et al 08A
post-QSO
starburst-like
quasar-like
Origin of Thermal Emission
• Quasar system evolves from cold --> warm
• In peak quasar phase, radiation /heating is dominated by AGN
• Starbusts and quasars have different IR-optical-Xray correlations
LFIR
SF
RLi et al 08
Lx (L⊙)
L FIR
(L ⊙
)
LB (L⊙)
L FIR
(L ⊙
)
Li et al 08B, in prep
Redshift z
LIR
(L
sun
)F
25u
m/F
60u
m
Li et al 08
• 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
III. Galaxies & Quasars in Cosmological Volume
quasar
galaxy
Li et al. 08C, in prep
starsY
(h-1
Mpc
)
X (h-1 Mpc)
BH
Log
Ifra
c
X (h-1 Mpc)Li et al 09, in prep
Summary
• CART is a powerful approach to study the formation, evolution, and multi-band properties of galaxies and quasars.
• Luminous z~6 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
• 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 --> quasar– Star formation history, evolved stellar components, mass functions– Metal enrichment, molecular gas, dust
• Thermal emission: stars --> AGN– SFR indicators– IR - optical relations
• End product: SMBH -- host correlations– MBH -- Mhost relation
Predictions & Observational Tests