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Formation of the first galaxies and reionization of the Universe:
current status and problems
A. Doroshkevich
Astro-Space Center, FIAN, Moscow.
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Theoretical expectations and observational problems
• Scientific activity: >17 publications in 2012• z~25 – 10 - formation of the first stars • and ionizing bubbles • Bubble model, UV-background, • non homogeneities in xH and Tg
• z~ 10 WMAP: τT~0.1, xH=nH/nb << 1• z~6.5 – 5 - high ionization, xH~10-3
• z< 3 - xH~10-5
• 1. We do not see any manifestations of the first stars• 2. We do not know the main sources of ionizing UV
radiation
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Universe Today 12.12.2012
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Possible sources of ionizing UV background
1. exotic sources – antimatter, unstable particles, etc…
2. First stars Pop III with Zmet<10-5 Z¤ or
3. non thermal sources - AGNs and Black Holes4. Quasars at z < 3.5, He III
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Reionisation• Θ(z)=α(T)n(z)H(z)~3T4
-0.7z103/2, T4~2. For z10>1
• recombination becomes important !Thermal sources: E~7MeV/baryon, Nγ< 5 105 /baryon Non thermal sources - AGNs and Black Hole
E~ 50MeV/baryon, Nγ~3.5 106 /baryon
Ωmet~2 10-6Ωbar~8 10-8, Ωbh~3 10-7Ωbar~ 10-8
• fesc~ 0.1 - 0.02, Nbγ~1 - 204.0
105108.05
7 b
esc
b
esc
bbrei Nf
NNfN
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Labbe I., 2010,ApJ.,708,L26, 1209.3037
• Spitzer photometry• Z~8, 63 candidats,• 20 actually detected• SMD for M<-18• ρ*(z=8)~106Ms/Mpc3
• Ω*(z=8)~0.4 10-5
• Ωmet(z=8)~0.4 10-7
• Ωreio~10-7 – 10-8
z~2.5, Ωmet~2.3 10-6 for IGM,
Ωmet~3 10-5 for galaxies
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Three steps of galaxy formation• 1. Formation of the virialized relaxed massive DM • cloud (perhaps, anisotropic) at z<zrec~103 with• ρcl ~200<ρ(z)> and overdensity δDM~104 z10
7M91/2
• 2. Cooling and dissipative compression of the baryonic• component, but the bulk motions and the kinetic • temperature of stars are preserved• 3. Formation of stars – luminous matter with M>MJ• Main Problem of the star formation• MJ/M¤~2·107T4
3/2nb-1/2,
• For stars: T4~10-2, nb>102cm-3 , MJ/M¤<103
• z=zrec,T4~0.3, nb~250 cm-3, MJ/M¤ ~2·105
• Parameters of baryonic components• <ρbar>~4·10-28z10
3g/cm3, <ρgal>~10-24g/cm3,• <ρstar>~1 g/cm3, ρBH~2 M8
-2g/cm3• Cooling factors: H2 molecules and metals (dust, C I etc.)•
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Simplest problem – first galaxies and POP III stars • Two processes of the H2 formation
• H+e=H-+γ, H-+H=H2+e, γ~1.6eV
• H+p=H2+ +γ, H2
++H=H2+p
• Epar=128K, Eort=512K
• In both case the reaction rate and the H2 concentrations are proportional to <ne>=<np>
• At 1000>z>zrei xe=ne/<n>~10-3 what is very small value.
• Feedback of LW radiation 912A<λ<1216A• H2+γLW =2H
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Influence of the LW background
• Actual limit is JLW21~1 – 0.1 for various redshifts• For the period of full ionization z~10 we get • JLW 21~4 Nbγ
• This means that at at 10>z>8.5 • the H2 molecules are practically destroyed and
star formation is strongly suppressed• This background is mainly disappeared at z~8.5
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Safranek-Shrader, 1205.3835
• Corrections• for both limits• ~10 times
• J21~4Nbγ
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Simulations (2001)• The box ~1Mpc, 128 -256 cells, • Ndm~107, mdm~30M0, Mgal~106 – 107 M0
• Very useful general presentation • (the galaxy and star formation are possible)• Restrictions:• a. small box → random regions (void or wall) &
unknown small representativity • b. large mass DM particles in comparison with
the mass of stars.
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What is mostly interesting
• a. realization – it is possible!• b. wide statistics of objects -- what is possible
for various redshifts• c. rough characteristics of internal structure of
the first galaxies• d. general quantitative analysis of main physical
processes
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Density – temperature 2001
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Machacek et el. 2001, ApJ, 548, 509• M~5 105Ms
• T4~0.3• nb~10cm-3
• fH2~3 10-5
• j21~1• MJ(25)~104Ms
• MJ(20)~500Ms
• Lazy evolution, • Monolitic object• Monotonic growth
ρ(z)??? Instabilities!
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Smith, B.,2008, MNRAS, 385, 1443
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Cooling functions.
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ρ, T & Z, Wise 1011.2632
• Formation of massive galaxies owing to the merging of low mass galaxies.
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Comments
• Importance – instead of the experiment • Complexity, representativity and precision
(WMAP). • Modern facilities• Our attempts – simulations versus analysis
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New semi analytical approach We know the process of the DM halo formation
and can use this information
• Assumptions:• a. what is the moment of halo formation• b. baryons follow to DM and have the same • pressure and kinetic temperature• c. what is the cooling of the baryonic • components• d. thermal instability leads to formation of • stars with masses Mst > MJeans
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Analytical characteristics for DM component• For the NFW halo with mass M=109 M9 Ms • formed at zf=(1+z)/10 • Within central core with r< rs we have• ρDM~10-23g/cm3M9
1/2zf10, TDM~40eV M9
5/6zf10/3mDM/mb
• Cooling factors: H2 and atomic for T4>1, • Three regimes of the gas evolution – • slack, rapid and isothermal• Thermal instability and the core formation• Stars are formed for Tbar<100K and nbar>100cm-3
• with Mstar > MJ ~5 107T43/2/nbar
1/2Ms
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Formation of the first stars with Mcl/M0 = 3 105 and 7 105, zf=24 (left)
and Mcl/M0=0.7 108 and 3 108, zf=11 (right)
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Low mass limit for the rapid-lazy formation of the first galaies
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SN explosions• W=GM2/Rvir~3·1055z10M9
5/3erg
• ESN~1052 – 1055 erg
• Dex<0.2 – 0.5 Mpc - IGM impact
• For M9>0.1 we have SN metal enrichment • within galaxy, otherwise – matter ejection• Low massive stars, satellites and merging
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Universe Today 1211.6804
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Ellis et al. arXiv1211.6804
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Bradley L., 1204.3641, UV luminosity function for z~8
• Low massive objects dominate
• Why?• Is this selection
effect?• What about object
collections? suppression of object formation ?
• What is at z=9? 10?
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• Behroosi et al. 1209.3013
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Behroozi et al., 1209.3013 - SFR(Mh)
• SMF~Mh-4/3, M>Mch; SMF~Mh
2/3, M<Mch (left panel)• Ms/Mh<2 – 3% at all z! ?continual evolution?
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comments• Stars occupy very small matter fraction ?• Low massive objects dominate at all redshifts? • Is this impact of nature or selection effect?• Formation of the massive galaxies owing to the • merging of satellites with stars?? • Illingworth 1977 for 13 E-galaxies• Fraction of massive objects increases more rapidly –
merging of satellites or other factors??• Small scale perturbations and missing satellite
problem – when and where had been formed dwarf galaxies.
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Tollerud et al. 2008, ApJ, 688, 277
• Observations of the Milky Way satellites with different corrections
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16 observed dSph galaxies (Walker et al.2009)dominated by DM component
• DM parameters• ρ~0.07M6
1/2f3(M6)
• P~37f4(M6)
• S~14M60.83/f(M6)
• Z10=0.9M6-0.1
• Bovill & Ricotti,• 2009, ApJ, 693,1859• Tollerud et al. 2008
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Conclusions• We do not see any manifestations of the first stars• We do not know the main sources of ionizing UV radiation • A. It seems that first stars Pop II & III , SNs, GRBs are approximately effective (~30 – 40%)• B. non thermal sources BHs remnants and/or
AGNs are more effective (~50% + ?)• C. We can semi analytically describe the formation
and evolution of the first galaxies
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Galaxies and BHs
BHs are observed in~1% of all galaxies, n~10-4Mpc-3
• Very massive BHs are observed as QSRs with • Nqsr~10-5 – 10-6 Mpc-3 at z<5; mainly at z~2 – 2.5• Perhaps, there are AGNs in 70% of old
massive galaxies. • ρBH~3 10-2M9
-2g/cm3, • ρDM~10-23zf
10M90.5g/cm3 within halo
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Vestergaard et al. 2008
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BH-distributions: M(z) & L/Led
Vestergaard, Osmer, 2009, ApJ,699,800
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Number density of the SMBH,Kelly et al., 2011, 1006.3561
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BH evolution• 1. We see rare supermassive BH at z<2 • - early formation and short lifetime.• 2. Impact of the accretion rate. • 3. Are the SMBH primordial? • 4. van den Bosch, Nature, arXiv:1211.6429• NGC 1277, M~1.2 1011M, MBH~1.7 1010M
• 5. Nature: Simcoe et al., 2012,• QSR ULASJ120+064, z=7.08, Zmet< 10-4Z
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SMBH formation
• Accretion of baryons from a thin/thick or HMD disk, major or minor mergers,
from Pop III BH remnants (Shapiro 2005). • Problems: small mass of remnants (<103M)• For the observed SMBHs MBH~(105 – 1010)M
• The expected mass amplification is (103 – 104).
• Primordial BH (Ricotti et al. 2007, Duching 2008)
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Three scenario of the BH formation
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The endThe end
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Redshift variations of intensity of the UV background
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SMGs, Yun et al., 1109.6286
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Behroozi et al., 1207.6105 Stellar mass vs. host haloSimilarity of the curves
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Gonzalez V., 2011, ApJ, 735, L34
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Observed galaxies and IGMΩmet as the cumulative measure
z~10 Ωreio >(1 – 8)10-8
• z~0, Ωmet~5.7 10-4
• z~2.5 Ωmet~3. 10-5 for galaxies with Mstar>109Mo
• z~7, Ωstar~4 10-6, • Ωmet~10-2Ωstar~4 10-8
• Possible explanations : • a. Low massive galaxies ?, b. non thermal sources c. strong non homogeneity (bubbles)
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UV luminosity densityOesch P., 2012, ApJ.745, 110
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MJ , Bromm et al., 1102.4638
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XXXXXX OBSERVATIONS• 5-year WMAP data:• τe=0.087±0.017, zrec=10.8±1.4• However: Pol~ΔT2τe, and ΔT2(DV)=2ΔT2(WMAP)
• Therefore, τe<0.9 and zrec<10.8• BUT• Quasars and galaxies are seen at z~8 - 9• τe~0.04 – 0.05, z~7
• τe~Δτe~0.001 – 0.06, 7< z <1000• One object at z~9.5,
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Observed galaxies and IGMΩmet as the cumulative measure
• We like to have at least• fesc~0.1 – 0.01, Nbp>1, Nph~5 105
• Ωmin=ΩbNbp(fescNph)-1~10-7(Nbp/fesc)(Ωb/0.04)• -----------------------------------------------------------------------------------------------------------------
• z~2.5, Ωmet~3 10-5 for galaxies,
• z~2.5, Ωmet~2.3 10-6 for IGM,• --------------------------------------------------------------------------------------------------------------------------------------
• z~5, Zmet=0.1Z~2 10-3,
• Ω*~6.7 10-5, Ωmet=Ω*Zmet~ 1.3 10-7 for galaxies
• ΩC~(5±1.7) 10-8, z<5.5, ΩC~(4.5±2.6) 10-9, z>5.5,