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S TRUCTURE F ORMATION IN THE U NIVERSE - THE FIRST ONE BILLION YEARS -. Naoki Yoshida National Astronomical Observatory. Niigata 3/12/2003. WMAP first year results. Early reionization ( ~200 million years ). Reionization sources. 1 What are they ? PopIII stars / - PowerPoint PPT Presentation
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STRUCTURE FORMATION IN THE
UNIVERSE- THE FIRST ONE BILLION YEARS -
Niigata 3/12/2003
Naoki YoshidaNational Astronomical Observatory
WMAP first year results
Early reionization( ~200 million years )
Reionization Reionization sourcessources
1 What are they ? PopIII stars / ordinary (PopII) stars ?
2 When did they form ? z > 20. Mostly z > 10 ?
3 Where ? in mini-halos/galaxies ?
4 How abundant ? 1/2/3 - peaks ?
1st generation 2nd generation
z = 22 z = 14~100 Myrs
10 Msun 7x10 Msun6 7
Cosmological Simulations of theCosmological Simulations of theFirst Generation ObjectsFirst Generation Objects
Gas H2
Primordial 9 species Non-equilibrium treatmente, H, H+, H-, H2, H2+, He, He+, He++
Matter density fluctuations (CDM + baryons + CMB photons)
Gravity Hydrodynamics
Chemical reactions
z = 100
N-body
Euler equation
• Collisional processes, recombinations
• Formation of H2 ( H + e H + h; H + H H2 + e )
• Photo-ionization, dissociation (UV background)
• Radiative cooling : collisional excitation, ionization, recombination, inverse-Compton Molecular hydrogen ro-vibrational lines (Galli & Palla 1998)
Chemical reactionsChemical reactionse, H, H+, H-, H2, H2+, He, He+, He++
31 reactions
- -
Primordial gas : 76% hydrogen, 24% helium
Very Early Structure Very Early Structure FormationFormation
Gas H2
Gas H2
Gas Dark matter
z=25
z=50
Gas DM
The first baryonic object !
Density distributions for baryons and dark matter
500 kpc
z=100
z=30
Early star-forming gas cloudsEarly star-forming gas clouds
1 Mpc
z=17
60million particles
100Msun pergas particle
Three important things:Three important things:
Characteristic mass of the first objectsCharacteristic mass of the first objects
Complex dynamical effectComplex dynamical effect
(galaxy clusters at z=0 (galaxy clusters at z=0 First First objects)objects)
Radiative feedbackRadiative feedback
Characteristic mass of the first Characteristic mass of the first objectsobjects
M_host ~ 10 Msun6
Yoshida, Abel, Hernquist, Sugiyama (2003a)
Simpler picture…
H He
H2
+
t_dyn ~ 30 Myrst_cool ~ 30 Myrst_chem ~ 30 Myrst_hubble ~ 100 Myrs
z=25:
Galaxy formation (20th century)“There’s a halo, yes! it’s a galaxy.”
Early gas clouds
Formation of CDM halos (5%)
Stars in molecular gas clouds HII regions + soft UV
““Fragile” hydrogen Fragile” hydrogen molecules molecules
J=10 erg sec cm Hz str (11.18 – 13.6 eV)
-23 -1 -2 -1 -1
Self-shielding againstsoft-UV radiation
Equilibrium abundance
No radiation
Substantial modulationdue to large H2 columnsin large halos (>> 10 cm )
core
14 2
Furthermore:
1 Lyman-series absorption by 1 Lyman-series absorption by “ “abundant” neutral hydrogenabundant” neutral hydrogen
2 Cosmological redshift2 Cosmological redshift (~11% increase in expansion parameter)(~11% increase in expansion parameter)
3 It is essentially a line-transfer problem in 3 It is essentially a line-transfer problem in 3D 3D
with a complex gas velocity fieldwith a complex gas velocity field (c.f. stationary gas in 1D case studied (c.f. stationary gas in 1D case studied by Ricotti et al. 2001)by Ricotti et al. 2001)
First star soft UV no more H2 cooling ?
Chemo-hydro cosmological simulation Jeans-unstable gas clouds
Massive PopIII star in the gas clouds
+ semi-analytic treatment of internal and external feedback
Adaptive ray-tracing to track the propagation of I-fronts(Sokasian 2003)
Evolution of ionization front
z=24 z=22
z=20 z=18
Sokasian, Yoshida, Abel, Hernquist (2003)
300 Msun Population III starper gas cloud
neutral
ionized
CDM model
Star Formation RateStar Formation Rate
Ionized Volume FractionIonized Volume Fraction
Only one star per star-forming region
Thomson Optical DepthThomson Optical Depth
Sokasian, Yoshida, Abel, Hernquist (2003)
Theoretical Studies on Cosmic Theoretical Studies on Cosmic ReionizationReionizationGnedin & Ostriker (1997-2000), Sokasian et al. (2003) Gnedin & Ostriker (1997-2000), Sokasian et al. (2003) -- Conventional picture z~7 (small box), too low optical depth-- Conventional picture z~7 (small box), too low optical depth
Ricotti et al. (2002)Ricotti et al. (2002) -- Small box. Resolution (~10^4 Msun) not enough for early objects.-- Small box. Resolution (~10^4 Msun) not enough for early objects.
Nakamoto & Umemura (2000)Nakamoto & Umemura (2000) -- Conventional picture z~7. Radiative transfer. (perhaps) too low optical depth-- Conventional picture z~7. Radiative transfer. (perhaps) too low optical depth
Yoshida et al. (2003a,b,c,d) Yoshida et al. (2003a,b,c,d) -- Small box size, high-res. (10^2-10^3 Msun), somewhat exotic massive PopIII -- Small box size, high-res. (10^2-10^3 Msun), somewhat exotic massive PopIII
Ciardi, Ferrara & White (2003)Ciardi, Ferrara & White (2003)-- Low-res. (10 Msun) DM simulation + SA gal.form. -- Low-res. (10 Msun) DM simulation + SA gal.form. No hydro. No hydro. gas clumping uncertain gas clumping uncertain
Cen(2003), Loeb et al. (2003), Fukugita & Kawasaki (2003), Haiman & Holder (2003)Cen(2003), Loeb et al. (2003), Fukugita & Kawasaki (2003), Haiman & Holder (2003) -- Press-Schechter. Many ingredients uncertain (C_clump, f_esc, c_star)-- Press-Schechter. Many ingredients uncertain (C_clump, f_esc, c_star) (most notably gas clumping)(most notably gas clumping)
Madau et al. (2003) Haiman, Abel, Rees (2000)Madau et al. (2003) Haiman, Abel, Rees (2000)-- Early quasars. Semi-analytic. Accretion efficiency onto BHs uncertain.-- Early quasars. Semi-analytic. Accretion efficiency onto BHs uncertain.
9
Suggestions:Suggestions:Correct gas clumping using hydrodynamic simulations (or clever idea)- A factor of 10 miss-estimate of gas clumping is similar to a factor of 10 enhanced photon production (_desired !)
Escape fraction from proto-galaxies- ~100% for mini-halos (Kitayama 2003), but ??? for the first galaxies- again, a factor of 2 …
Formation of early generation stars, instead of “THE” very first star- Are all the first stars massive as ABN and Omukai suggest ?
Population III likely unimportant in photon-production,but not negligible (even very important) in terms of IGM clumpingand subsequent gas cooling in larger halos
Formation of dense gas clouds in proto-galaxies- First disk galaxies
Pre-heating at z=20Pre-heating at z=20
J=10 erg sec cm Hz str (100,000 K thermal)
-21 -1 -2 -1 -1
A Hubble time (~ 2 dynamical times) A Hubble time (~ 2 dynamical times) later :later :
Gas DM
THERMODYNAMIC EVOLUTION
20 Myr after 50 Myr 100 Myr
before reionization
after (brief) reionization
CHEMICAL EVOLUTION
1st object 2nd generation object
H2 cooling plays a role in both cases!
FIRST STARS AS AN ORIGIN FIRST STARS AS AN ORIGIN OFOF
HEAVY ELEMENTSHEAVY ELEMENTS
Metals at high-zMetals at high-z CCIVIV at z~5 at z~5 (Songaila 2001, constant at z=3-5)(Songaila 2001, constant at z=3-5)
Damped Lyman-Damped Lyman- systems at z=3-5 systems at z=3-5 (Prochaska 2002)(Prochaska 2002)
FeFeIIII emission from z=6 quasars emission from z=6 quasars (Freudling, Corbin, Korista 2003)(Freudling, Corbin, Korista 2003)
Silicon in intra-cluster mediumSilicon in intra-cluster medium (abundance (abundance anomaly)anomaly)
(Baumgartner et al.(Baumgartner et al. 2003)2003)
BlackholesBlackholes (( Inoue & Chiba 2003Inoue & Chiba 2003 ; ; Merritt & Ferarrese Merritt & Ferarrese
2001) 2001)
Where did they come from…?
Massive Population III stars(100-300 Msun )
Massive Population III stars:Massive Population III stars:1. Very luminous
2. Efficient metal factory
3. Powerful metal distributor
A 200 Msun star ⇒ 3x10 UV photons64
( Early reionization inferred from the WMAP data )
A 200 Msun star ⇒ ~ 90 Msun helium core
ζ= = 5x10Nγ
N Z -6
The death of the first stars(Bromm, Yoshida & Hernquist 2003)
M ~ 10 Msun6
1 kpc
The first supernova The first supernova explosionexplosion
Esn ~ 10 ergs(PISN, Hypernovae)
53
1kpc
Remnant cools byInverse Compton SZ sources!
Initial density fluctuations
Formation of halos
Gas heating/cooling
Molecular gas cloudformation
Massive stars
Z
analytic model
Nbody/hydro+RT
ζ= = 5x10Nγ
N Z -6
Star formation history in the early Star formation history in the early universeuniverse
necessarynecessary expectedexpected
Thomson optical depth
High-z IGM
Cluster ICM
Δτ ~ 0.05
ΩCIV ~ 3 x 10-8
ΩPopIII~ 10 -5
Δτ~ 0.06
ΩCIV ~ 10-8
ΩPopIII~ 5 x 10 -7
(Songaila 2001)
(Baumgartner et al. 2003)
PopIII
Prospects for observation
~nJy sensitive NIR instrument
Direct imaging21 cm emissionH2 linesInfrared-missions (H/HeII lines)High-z GRBs (afterglow)Planck satellite (not only )
BRIGHT FUTURE FOR
イオン化波面の伝播
Adaptive RayCastingScheme
N
ne,np
Ri
Ri+1
dt
モデル :
1. ガス雲につき一つの PopIII 星 2. f_esc = 13. イオン化領域では星形成なし
イオン化領域の割合
Thomson optical depthWMAP TE detection
CDM
Pop II only
WDM
dzdz
dtcn
z
eT
(原始)銀河でできた星
赤方偏移
Metal yield of a PopIII starMetal yield of a PopIII star
Heger & Woosley (2002)
Prospects for observations Prospects for observations
1. Determination of reionization history (not only ) by post-WMAP CMB experiment,
by observations of GRB afterglows (see poster by Ioka).
2. Huge Lyman- forests sample from SDSS as well as gal.-gal. power spectrum.
3. Observations of galactic lens systems (Metcalf et al. 2003; Dalal & Kochanek
2003).