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Formation of the first galaxies and reionization of the Universe: current status and problems

This article discusses the formation of the first galaxies and the reionization of the universe, focusing on the current status and unresolved issues. It explores theoretical expectations and observational challenges, including the lack of evidence for the first stars and uncertainty regarding the sources of ionizing UV radiation.

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Formation of the first galaxies and reionization of the Universe: current status and problems

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

  2. 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

  3. Universe Today 12.12.2012

  4. 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 Holes 4. Quasars at z < 3.5, He III

  5. 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 • fesc~ 0.1 - 0.02, Nbγ~1 - 2 Ωmet~2 10-6Ωbar~8 10-8, Ωbh~3 10-7Ωbar~ 10-8

  6. 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 Labbe I., 2010,ApJ.,708,L26, 1209.3037 z~2.5, Ωmet~2.3 10-6 for IGM, Ωmet~3 10-5 for galaxies

  7. 1. Formation of the virialized relaxed massive DM cloud (perhaps, anisotropic) at z<zrec~103with ρcl ~200<ρ(z)> and overdensity δDM~104 z107M91/2 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¤~2·107T43/2nb-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>~4·10-28z103g/cm3, <ρgal>~10-24g/cm3, <ρstar>~1 g/cm3, ρBH~2 M8-2g/cm3 Cooling factors: H2 molecules and metals (dust, C I etc.) Three steps of galaxy formation

  8. 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>~10-3what is very small value. Feedback of LW radiation 912A<λ<1216A H2+γLW =2H Simplest problem – first galaxies and POP III stars

  9. 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

  10. Corrections for both limits ~10 times J21~4Nbγ Safranek-Shrader, 1205.3835

  11. 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.

  12. 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

  13. Density – temperature 2001

  14. 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! Machacek et el. 2001, ApJ, 548, 509

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

  16. Cooling functions.

  17. Formation of massive galaxies owing to the merging of low mass galaxies. ρ, T & Z, Wise 1011.2632

  18. Comments • Importance – instead of the experiment • Complexity, representativity and precision (WMAP). • Modern facilities • Our attempts – simulations versus analysis

  19. New semi analytical approachWe 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

  20. 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/cm3M91/2zf10, TDM~40eV M95/6zf10/3mDM/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/nbar1/2Ms

  21. 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)

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

  23. W=GM2/Rvir~3·1055z10M95/3erg ESN~1052 – 1055erg Dex<0.2 – 0.5 Mpc- IGMimpact For M9>0.1 we have SN metal enrichment within galaxy, otherwise – matter ejection Low massive stars, satellites and merging SN explosions

  24. Universe Today 1211.6804

  25. Ellis et al. arXiv1211.6804

  26. 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?

  27. Behroosi et al. 1209.3013

  28. SMF~Mh-4/3, M>Mch; SMF~Mh2/3, M<Mch (left panel) Ms/Mh<2 – 3% at all z! ?continual evolution? Behroozi et al., 1209.3013 - SFR(Mh)

  29. 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. comments

  30. Observations of the Milky Way satellites with different corrections Tollerud et al. 2008, ApJ, 688, 277

  31. 16 observed dSph galaxies(Walker et al.2009)dominated by DM component • DM parameters • ρ~0.07M61/2f3(M6) • P~37f4(M6) • S~14M60.83/f(M6) • Z10=0.9M6-0.1 • Bovill & Ricotti, • 2009, ApJ, 693,1859 • Tollerud et al. 2008

  32. 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

  33. 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~10-23zf10M90.5g/cm3 withinhalo

  34. Vestergaard et al. 2008

  35. BH-distributions: M(z) & L/LedVestergaard, Osmer, 2009, ApJ,699,800

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

  37. 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☼ BH evolution

  38. 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)

  39. Three scenario of the BH formation

  40. The end The end

  41. Redshift variations of intensity of the UV background

  42. SMGs, Yun et al., 1109.6286

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

  44. Gonzalez V., 2011, ApJ, 735, L34

  45. Observed galaxies and IGMΩmetas 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 withMstar>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)

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

  47. MJ , Bromm et al., 1102.4638

  48. 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,

  49. Observed galaxies and IGMΩmetas 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,

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