Transcript Formation of the Most Distant & Luminous Quasars

Quasars at the Cosmic Dawn
Yuexing Li
Penn State University
Main Collaborators: Lars Hernquist (Harvard)
Volker Springel (Heidelberg)
Tiziana DiMatteo (CMU),
Liang Gao (NAOC)
The Most Distant Quasars Discovered
Presence of SMBHs to power these
quasars, MBH~109 M⊙ at z>6
Presence of large stellar component in host
galaxies, Mstar > 1011 M⊙
Presence of copious molecular gas
Mgas~1010 M⊙ and dust Mdust~108 M⊙ in
the quasar hosts
Fan+06
Questions & Myths
I: Can such massive objects form so early in the
LCDM cosmology?
– myth: there is a “cut-off” at z~5 (Efstathiou & Rees 88)
– myth: some 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
CART
Cosmological All-wavelength Radiative Transfer
Multi-scale Cosmological Sims
(GADGET2 Springel 05)
+
ART2
(Li et al 08)
(All-wavelength Radiative Transfer with
Adaptive Refinement Tree)
Formation, evolution & multi-band properties
of galaxies & quasars
Formation of z~6 Quasars from
Hierarchical Mergers
• Multi-scale simulations
–
–
–
–
–
cosmological simulation in 3 Gpc3
Identify dark matter 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
• Each galaxy progenitor contains a 100 M⊙ BH seed
– Left behind by PopIII stars
– Grows at Eddington rate until it enters merger tree (104-5 M⊙)
• Self-regulated BH growth model
– Bondi accretion under Eddington limit
– Feedback by BHs in thermal energy coupled to gas
Co-evolution of
SMBHs and Host
Age of Universe (Gyr)
• <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
Redshift z
Evolution of SEDs
quasar-like
starburst-like
post-QSO
obs (m)
Li et al 08
Origin of Thermal Emission
LFIR
(L⊙)
LFIR
(L⊙)
• 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
Lx (L⊙)
LB (L⊙)
Z>6 Galaxies & Quasars in a
Cosmological
Volume
stars
BH
Log Ifrac
Y (h-1 Mpc)
• SPH cosmological simulations with BHs
• They form in massive halos in overdense
regions
galaxy
• They are highly clustered
• May provide patchy ionization of HIquasar
X (h-1 Mpc)
X (h-1 Mpc)
Predictions for Future Surveys
JWST
Can z>6 SMBHs form
from ~100 M⊙ BH seeds?
• BHs from PopIII stars at z~20-30 may have ~100 M⊙
• This would require BHs accrete at near Eddington rate
for much of its early life
• Previous studies suggest that radiative feedback
strongly suppresses BH accretion rate
– Johnson & Bromm 07, Alvarez+08: AR <1% Eddington
– Milosavljevic+08,09: AR ~30% Eddington
• However, we should note that
– Not every BH seed grows into a SMBH
– Small box in simulations may prevent gas replenish
– Self-gravity may boost accretion
Accretion onto ~100 M⊙ BH
Seeds
• 1-D spherical accretion, including gas selfgravity
– Modified VH1 code (Blondin & Lufkin 93)
– Logarithmic grid, 10-4 -1 pc
• Feedback processes
– Photoionization heating
– Radiation pressure
• Thomson scattering
• photoionization
Self-gravity Aided Accretion
Self-gravity Aided Accretion
Summary
• The first SMBHs can form from ~100 M⊙ BH seeds in
high overdensity peak with abundant gas supply,
because self-gravity overcomes radiative feedback and
boots accretion rate
• Luminous z~6 quasars can form in the LCDM
cosmology via hierarchical mergers of gas-rich protogalaxies
• 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
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 --> 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