Formation of the first galaxies and reionization of the Universe:

current status and problems

A. Doroshkevich

Astro-Space Center, FIAN, Moscow.

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

Universe Today 12.12.2012

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

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

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

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.)•

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

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

Safranek-Shrader, 1205.3835

• Corrections• for both limits• ~10 times

• J21~4Nbγ

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.

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

Density – temperature 2001

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!

Smith, B.,2008, MNRAS, 385, 1443

Cooling functions.

ρ, T & Z, Wise 1011.2632

• Formation of massive galaxies owing to the merging of low mass galaxies.

Comments

• Importance – instead of the experiment • Complexity, representativity and precision

(WMAP). • Modern facilities• Our attempts – simulations versus analysis

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

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

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)

Low mass limit for the rapid-lazy formation of the first galaies

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

Universe Today 1211.6804

Ellis et al. arXiv1211.6804

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?

• Behroosi et al. 1209.3013

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?

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.

Tollerud et al. 2008, ApJ, 688, 277

• Observations of the Milky Way satellites with different corrections

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

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

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

Vestergaard et al. 2008

BH-distributions: M(z) & L/Led

Vestergaard, Osmer, 2009, ApJ,699,800

Number density of the SMBH,Kelly et al., 2011, 1006.3561

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

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)

Three scenario of the BH formation

The endThe end

Redshift variations of intensity of the UV background

SMGs, Yun et al., 1109.6286

Behroozi et al., 1207.6105 Stellar mass vs. host haloSimilarity of the curves

Gonzalez V., 2011, ApJ, 735, L34

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)

UV luminosity densityOesch P., 2012, ApJ.745, 110

MJ , Bromm et al., 1102.4638

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,

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,