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The first sources of light in the Early Universe and the highest plausible redshift of luminous Quasars


COBE data reveal fluctuations in CMB in mK domain. Large scale CMB ... results: flat universe with LCDM cosmology. L 0 WL ~ 0.62. WB ~ 0.05 WCDM ~ 0.33 ... – PowerPoint PPT presentation

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Title: The first sources of light in the Early Universe and the highest plausible redshift of luminous Quasars

The first sources of light in the Early Universe
and the highest plausible redshift of luminous
  • Andreas Müller
  • Landessternwarte Heidelberg
  • Oberseminar 2001
  • Entstehung von Quasaren

The Cosmological Setup
Primordial Objects
Cosmological Ingredients
The Lya Forest
zreion measurements
Gnedin Simulations
Reionization Tools
Future Instruments Challenges
A flat LCDM Universe
  • Gamov 1948 hypothesis of CBR afterglow
  • 3K-radiation isotropic (Penzias Wilson 1964)
  • a Big Bang relic
  • COBE data reveal fluctuations in CMB in mK domain
  • Large scale CMB temperature anisotropy
  • a confirmed by new instruments with higher
  • resolution (x 30) balloon experiments
  • a Detection of seed clumps for galaxy formation
  • results flat universe with LCDM cosmology
  • L gt 0 WL 0.62
  • WB 0.05 WCDM 0.33
  • WHDM 0.001 (n) Wtot 1.0
  • inflation compatible

Milestones in the history of the Universe
Fragmentation of Primordial Objects
  • Collapsing DM mini halos at z 30
  • SPH simulations
  • Initial mass 2 x 106 M8
  • Cooling via H2 chemistry from Tgas 104 K
  • to the CMB floor of 86 K
  • Fragmentation to high-density clumps
  • (n gt 108 cm-3)
  • Clump growing by gas accretion and merging
  • to 104 M8 clumps
  • a first PopIII stars rather massive!
  • Recently metallicity effects included
  • gas with higher metallicities settles into
  • center of DM halos!
  • need pre-enrichment event for Z 10-3Z8

Bromm et al. 2001
Gas-Clump Morphology at z 28
30 pc
Bromm et al. 2001
The high-mass Progenitors Protogalactic DM
18 small blue objects collisions and merging Ä
each in 4 Gpc distance growing Ä
each several billion stars hierarchical structure
The Hierarchical Structure
  • z 30 1st generation of stars and quasars
  • Reionization of most H in the universe at z 7
  • Current observations at threshold for probing
  • H reionization epoch!
  • Tool observational study of HZ sources
  • CMB anisotropies small density fluctuations
  • a large-scale structure of the universe (LSS)
  • Gravitational collapses in dense regions a clumpy
  • Constraint by observations evolution of galaxies
    at z lt 6
  • Elementary building blocks 1st gaseous objects
    with Jeans mass ( 104 M8) a formed in SCDM
    models at z 15-30
  • Evolution of the Universe
  • homogeneous, isotropic, simple a clumpy,

The Cosmological Ingredients and Numerics
  • Simple setup
  • i) primordial power spectrum of Gaussian
    density fluctuations
  • ii) DM mean density
  • iii) initial temperature and density of cosmic
  • iv) primordial composition by Big Bang
  • v) lack of dynamically-significant magnetic
  • Analytics early evolution of seed density
  • Numerics collapse and fragmentation of nonlinear
  • Tools HD simulations, SPH, N-Body, Radiative
  • 1st light from stars and quasars ended the dark
    ages (Rees) of the universe a renaissance of
  • Reionization epoch

Lya Forest Reionization Redshift
overlapping bubbles
first ionisators
emanating HII regions
  • lc 912 A
  • absorption by photoionization
  • of H and He

la 1216 A lb 1026 A
Optical spectrum of Quasar with z 5.8
observational diagnosis Universe is fully
ionized at z 5.8! When and how was the IGM
Fan et al. 2000
Key ingredients for Reionization
  • Need intergalactic ionizing radiation field
  • a Radiative Feedback
  • Sources/Ionisators escape radiation of
  • first stars Quasars
  • current reionization models with isotropic point
    sources (Gnedin 2000, Miralda-Escudé et al. 1999)
  • Sources embedded in densest regions (halos)
  • Constraint reionization simulation resolution
  • Simplification point sources in large-scale IGM!
  • Challenges
  • clumpiness (radiation affected strongly by
    inhomogeneous effects)
  • HD feedback (winds, SN)

Ionization fronts in the IGM
  • radiation of first ionisators a HII bubbles
    (Strömgren spheres)
  • H ionization threshold 13.6 eV
  • Stellar ionizing spectrum most photons above
  • CS high a thin HI layer suffices to absorb all
  • no He contributions!
  • Model assumptions spherical ionized volume
  • Recombination very high in high-density clumps
  • Maximum comoving radius (neglect recombination,
  • SCDM WB 0.045, WM 0.3, WL 0.7 Ng
    ionizing photons
  • per baryon, Nion ionizations per baryon, M
    halo mass,
  • n0H present number density of H)

Loeb et al. 2000
Reionization of Hydrogen in the IGM
I initial pre-overlap stage
individual sources escape photons find their way
through high-density regions (high recombination
rate!) IGM is two-phase medium a highly ionized
regions a neutral regions ionization intensity
very inhomogeneous
Reionization of Hydrogen in the IGM
II rapid overlap phase of reionization
higher exposition by ionizing photons! a
ionization intensity increases rapidly a
expansion into high-density gas a several
unobscured sources a ionization intensity more
Reionization of Hydrogen in the IGM
II moment of reionization
ionization radiation does NOT reach
self-shielded, high-density clouds a end of
overlap phase
Reionization of Hydrogen in the IGM
III post-overlap phase This continues
indefinitely, since collapsed objects retain
neutral gas even in present universe. Milestone
at zbr 1.6 a breakthrough redshift Below
zbr all ionizing sources are visible! Above zbr
absorption by Lya forest clouds a Only sources
in small redshift range are visible!
Reionization of Hydrogen in the IGM
  • Vmax 4/3prmax3
  • solid source switch-on _at_ z 10
  • dashed source switch-on _at_ z 15

Scalo et al. (1998)
Evolution of filling factor
  • Nion 40
  • clumping factor
  • C const
  • dashed collapse
  • fraction Fcol
  • dotted obs. lower limit for zreion
  • (Fan et al. 2000)
  • Recombination less important
  • at HZ!

Loeb et al. 2000
  • Star-forming galaxies in CDM hierarchical models
    can explain reionization of the universe
  • at z 6 15
  • Further contributes for ionization by
  • mini-quasars is possible
  • uncertain parameters for determining zreion
  • Source parameters
  • formation efficiency of stars and quasars
  • escape fraction of ionizing sources
  • Clumping factor C depends on the density and
    clustering of the sources
  • source halos form in overdense regions
  • a C depends on sources and IGM density

Gnedin 2000 - Stellar Reionization Simulations
  • LCDM with Wm 0.3
  • radiative transfer code
  • periodic boundary conditions
  • 1283 DM, 1283 baryonic particles (mb 5x105 M8)
  • thin slices through a Mpc box with 4 h-1 per side
  • J21 mean ionization intensity at Lyman limit
  • (in units of 10-21 erg cm-2 s-1 sr-1 Hz-1)
  • J21 inside HII regions depends on absorption and
    RT through IGM
  • includes local optical depth effects
  • does not include shadowing

Gnedin 2000 Reionization Simulations
z 11.5
redshift evolution of log from mean ionization
log of HI fraction
gas density
gas temperature
Gnedin 2000 Reionization Simulations
z 9.0
Gnedin 2000 Reionization Simulations
z 7.7
Gnedin 2000 Reionization Simulations
z 7.0
Gnedin 2000 Reionization Simulations
z 6.7
Gnedin 2000 Reionization Simulations
z 6.1
Gnedin 2000 Reionization Simulations
z 5.7
Gnedin 2000 Reionization Simulations
z 4.9
Gnedin 2000 - Stellar Reionization Simulations
  • ionized bubbles emanate from main
  • concentrations of sources
  • sources located in highest density regions (C
  • bubbles expand in low density regions in IGM
  • finally bubbles overlap
  • complex topology of ionized regions
  • neutral islands remain in highest density regions
  • But rough approximations in RT have to be
    treated more accurately and then explored in

Quasar Reionization
Stellar Reionization
  • bright point-source
  • a HII funnel (in disk)
  • a photons escape through channel!
  • hard quasar photons
  • a penetrate deeper into neutral gas
  • a thicker ionization front
  • Quasar X-photons catalyze H2 molecule formation
  • a stars form in tiny halos (Haiman, Abel Rees,
  • BUT hardness of ionization spectrum depends of
  • initial mass function!

The Loeb-Rybicki halo
  • Diffuse Lya halos due to Hubble expansion
  • Tool for probing distribution and velocity field
    of neutral IGM before epoch of reionization
  • Disappearance of Lya halos signals zreion !
  • Detection challenge
  • low surface brightness!

21cm tomography in the pre-reionization epoch
  • Hyperfine structure transition spin-flip from
  • triplet to singlet state traces HI regions
  • Observability
  • ground-state thermalizes with CMB
  • perturbation of thermal equilibrium by collisions
  • and scattered Lya photons
  • map redshifted 21cm emission at HZ to reveal
    neutral pre-ionization IGM (pre-overlap stage I)
  • Instruments Square Kilometer Array (SKA)

The Evolution of the SFR
hSFR 10 (obs. indicated)
Blain et al. 1999
upper total SFR
lower NGST fract. flim 0.25 nJy
Reionization s Reheating s Suppressed SFR
Barkana Loeb 2000
He - Reionization
  • HeI a He II by 24.6 eV photons
  • He II ionization threshold _at_ 54.4 eV
  • a Reionization of He II later (lower z!) than HI
  • a He - Reionization more observable! (H
  • nH/nHe 13 He more rare a no prob!
  • Observational probe
  • heating of IGM due to hard ionisators
  • a H reionization TIGM 104 K
  • a He reionization TIGM gt 2 x 104 K
  • a hotter IGM suppresses dwarf galaxy formation
  • TIGM measurements
  • search for smallest line-widths
  • among H Lya absorption lines
  • Schaye et al. 2000
  • isothermal IGM with T 2 x 104 K _at_ z 3

He II Lya absorption in the IGM Q 0302-003 z
Heap et al. (2000)
Q 0302-003 - Interpretation
  • Lya absorption by intergalactic He II
  • fits data for low-density IGM
  • sharp opacity break at z 3.0 (l 1240 A)
  • a sudden hardening of UV ionizing
  • background below z 3
  • a high opacity only requires 0.1 of
  • He not fully ionized
  • confirmation by indirect diagnosis Si-4/ C-4
  • (Songaila Cowie 1996, Songaila 1998)
  • Overlap phase of full He reionization
  • at higher z!

NCSA simulation Norman et al. 1997
  • Numerical hydrodynamics
  • simulation of the Lya forest
  • gas density distribution at z3
  • CDM spectrum of primordial density fluctuations
  • H0 50 km/s
  • comoving box size of 9.6 Mpc
  • Wb 0.06 ( 76 H, 24 He)
  • cube side 2.4 Mpc (proper)
  • Isosurfaces baryons at ten times mean
  • cosmic density
  • Tgas 3 x 104 K (dark blue)
  • Tgas 3 x105 K (light blue)
  • single random slice through cube shows baryonic
    overdensity represented by a rainbow--like color
    map (blackmin to redmax)
  • HeII mass fraction wire mesh in same slice (fine
  • fine structure in minivoids rescaled mass
    fraction in
  • overdense regions by gas overdensity wherever it
    exceeds unity.

(No Transcript)
The Reionization Challenge
  • How much ionizing sources are available?
  • a Extrapolation from observed populations of
    galaxies and quasars to HZ (Madau et al. 1999,
  • Miralda-Escudé et al. 2000)
  • a Conclusion
  • HZ source population is similar to the one
    observed at z 3 4 and suffices to produce
  • the J21 needed!
  • a But
  • ? Escape fraction ?
  • ? Luminosity function ?
  • ? Clumping factor ?
  • ? Recombination ?
  • WANTED! further constraining observations

Future Instruments
  • Observational efforts to dive into HZ regime
  • further space-telescopes large ground-based
    telescopes (optical 30 m diameter radio SKA)
  • NGST (launch 2009 planned)
  • sub-nJy sensitivity in IR range (1-3.5 mm)
  • probing optical-UV sources at z gt 10
  • Popular CDM models predict 1st baryonic
  • objects at z 10
  • Future change focus from
  • LSS (Large Scale Structure)
  • to
  • SSS (Small Scale Structure)
  • Waiting for observational input data from
  • NGST, MAP, Planck, CAT, CBI SKA
  • Next decade high precision cosmology

Primordial Objects at z 30
Lya Systems probe Reionization epoch z 7
Reionization studies by LR halo, 21cm, SFR
Tune and Refine Simulations
Constraints by Observational Input
Cosmology in the 21. Century SSS
  • Loeb a astro-ph/0010467, 0011529
  • Gnedin a astro-ph/0002151, 0008469, 9909383
  • Fan a astro-ph/0005414
  • Heap a ApJ 534, 69-891 (2000)
  • Schaye a astro-ph/9912432
  • Bromm a astro-ph/9910224, 0103382, 0104271
  • URLs
  • http//
  • http//
  • http//
  • http//
  • http//zeus.ncsa.uiuc.edu8080/LyA/minivoid.html