Formation of the first galaxies and reionization of the Universe: current status and problems A. Doroshkevich Astro-Space Center, FIAN, Moscow.

What we know about early Universe z~25 – 10 - formation of the first galaxies and ionizing bubbles Bubble model, UV-background, non homogeneities in x H and T g z~ 10 WMAP: τ T ~0.1, x H =n H /n b << 1 z~6.5 – 5 - high ionization, x H ~10 -3 z< 3 - x H ~ 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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Possible sources of ionizing UV background 1.exotic sources – antimatter, unstable particles, etc… It is not popular, but there is new publication - e First stars Pop III with Z met <10 -5 Z ¤ or 3. non thermal sources - AGNs and Black Holes 4. Quasars at z < 3.5, He III - observed

Reionisation Θ(z)=α(T)n(z)H(z)~3T z 10 3/2, T 4 ~2. For z 10 >1 Restrctions for the UV background Thermal sources: E~7 MeV/baryon, N γ < /baryon Non thermal sources - AGNs and Black Hole E~ 50 MeV/baryon, N γ ~ /baryon Ω met ~ Ω bar ~ , Ω bh ~ Ω bar ~ In all the cases very small baryon fraction is used f esc ~ , N bγ ~1 - 2

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Ellis et al. arXiv

Behroosi et al – This is important!

Labbe I., 2010,ApJ.,708,L26, Spitzer photometry Z~8, 63 candidats, 20 actually detected SMD for M<-18 ρ * (z=8)~10 6 M s /Mpc 3 Ω * (z=8)~ Ω met (z=8)~ Ω reio ~10 -7 – z~2.5, Ω met ~ for IGM, Ω met ~ for galaxies

Three steps of galaxy formation 1. Formation of the virialized relaxed massive DM cloud (perhaps, anisotropic) at z<z rec ~10 3 with n b ~44z f 10 M 9 1/2 cm -3, T b ~14z f 10/3 M 9 5/6 eV, z f =(1+z)/10 2. Cooling and dissipative compression of the baryonic component, thermal instability 3. Formation of stars – luminous matter with M>M J Main Problem of the star formation M J /M ¤ ~2 ·10 7 T 4 3/2 n b -1/2, For stars: T 4 ~10 -2, n b >10 2 cm -3, M J /M ¤ <10 3 z=z rec,T 4 ~0.3, n b ~250 cm -3, M J / M ¤ ~ 2 ·10 5 Parameters of baryonic components ~4· z 10 3 g/cm 3, ~ g/cm 3, ~1 g/cm 3, ρ BH ~2 M 8 -2 g/cm3 Cooling factors: H 2 molecules and metals (dust, C I etc.)

First galaxies and POP III stars Two processes of the H 2 formation H+e=H - +γ, H - +H=H 2 +e, γ~1.6eV H+p=H 2 + +γ, H 2 + +H=H 2 +p E par =128K, E ort =512K The reaction rate and the H 2 concentrations are proportional to = At 1000>z>z rei x e =n e / ~10 -3 what is very small value. Feedback of LW radiation 912A<λ<1216A H 2 +γ LW =2H Feedback of the IR radiation ~8000 A

Key problem - star formation Three factors: x e, LW & IR Cooling factors: H 2 and atomic for T 4 >1, Three regimes of the gas evolution – slack, rapid and isothermal Thermal instability and the core formation Stars are formed for T bar 100cm -3 with M star > M J ~ T 4 3/2 /n bar 1/2 M s

Formation of the first stars with M cl /M 0 = and , z f =24 (left) and M cl /M 0 =10 9 and , z f =11 (right)

Influence of the LW & IR backgrounds Actual limit is J LW21 ~1 – 0.1 for various redshifts For the period of full ionization z~10 we get J LW 21 ~4 N bγ This means that at 10>z>8.5 the H 2 molecules are practically destroyed and star formation is strongly suppressed This background is mainly disappeared at z~8.5

Safranek-Shrader, Corrections for both limits ~10 times J 21 ~4N b γ

Alternatives for the star radiation Hard UV and X-rays from the BH In the case T b ~10 4 K and thermal ionization but we get the high entropy of baryonic component and increasing of minimal mass, M gal >M J ≈ T 4 3/2 z f -3/2 M o It is not catastrophic ! What is the best way?

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

Simulations (2001) The box ~1Mpc, cells, N dm ~10 7, m dm ~30M 0, M gal ~10 6 – 10 7 M 0 Very useful general presentation (the galaxy and star formation are possible) Restrictions: a. small box → random regions (void or wall) & unknown small representativity b. low massive halos, weak interaction of halos c. stars are outer model parameters d. large mass DM particles in comparison with the mass of halos.

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

ρ, T & Z, Wise Formation of massive galaxies owing to the merging of low mass galaxies.

Machacek et el. 2001, ApJ, 548, 509 M~ M s T 4 ~0.3 n b ~10cm -3 f H2 ~ j 21 ~1 M J (25)~10 4 M s M J (20)~500M s Lazy evolution, Monolitic object Monotonic growth ρ(z)??? Instabilities!

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 (~20 – 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 Observations: galaxies ↔ background – A – James Webb

The end

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 M st > M Jeans

Bradley L., , 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?

Behroozi et al., SFR(M h ) SMF~M h -4/3, M>M ch ; SMF~M h 2/3, M<M ch (left panel) M s /M h <2 – 3% at all z! ?continual evolution?

Analytical characteristics for DM component For the NFW halo with mass M=10 9 M 9 M s formed at z f =(1+z)/10 Within central core with r< r s we have ρ DM ~ g/cm 3 M 9 1/2 z f 10, T DM ~40 eV M 9 5/6 z f 10/3 m DM /m b Cooling factors: H 2 and atomic for T 4 >1, Three regimes of the gas evolution – slack, rapid and isothermal Thermal instability and the core formation Stars are formed for T bar 100cm -3 with M star > M J ~ T 4 3/2 /n bar 1/2 M s

Behroozi et al., Stellar mass vs. host halo Similarity of the curves

Gonzalez V., 2011, ApJ, 735, L34

UV luminosity density Oesch P., 2012, ApJ.745, 110