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History of Cosmological Reionization

History of Cosmological Reionization. Renyue Cen Princeton University Observatory @End of Dark Ages Workshop (STScI) March 14, 2006. History of cosmic structure formation Observational constraints on reionization Reionization process calculations

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History of Cosmological Reionization

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  1. History of Cosmological Reionization Renyue Cen Princeton University Observatory @End of Dark Ages Workshop (STScI) March 14, 2006 • History of cosmic structure formation • Observational constraints on reionization • Reionization process calculations • Numerical radiative transfer simulations • Detecting first galaxies • Conclusions

  2. The Standard Cosmological Model n=0.99, s8 = 0.9, Wbh2=0.024, Wxh2 = 0.126, H0 = 72, L0= 0.71 (subject to adjustments in 2 days) • Adiabatic, Gaussian, scale-free density perturbation • --- Baryons 5% • --- Cold Dark Matter 23% • --- Dark Energy (cosmological constant?) 72% Spergel etal (2003) • consistent with: • Inflation • Light element • nucleosynthesis • q0 from SNe Ia • H0 (HST key • project, SNe Ia) • Age of the universe • (stellar evolution) WHIM

  3. Cosmic Timeline in Standard Model 0.0003 Time  13 Gyr  Redshift 106K 30 – 15 10-6 6 - 1 1 - 0 z=1100 Real Dark Ages Pop III Stars Galaxies Quasars 1st Reion 2nd gen Galaxies Quasars Final Reion Lya forest Majority of Quasars Ellipticals Majority of Galaxy Clusters LSS Recom- bination 3000 K 10000 K Temp 100K Hierarchical structure formation        …………………………………..       Log(Mnl) 105 106 108 109 1012 1014

  4. Observ. Constraints on Reionization 1: SDSS QSOs: neutral hydrogen fraction changes from 10-4 to>10-2 from z=5.8 to 6.3 Cen & McDonald (2002) Fan et al (2002) SDSS 1030+0524 z=6.28 Put Fan fig6 here Naïve implication: te=0.03-0.04

  5. More new z>6 quasars White, Becker, Fan, Strauss (2003)

  6. 2: WMAP (1st Yr): te=0.17 +- 0.04 Kogut et al. 2003 Bennett et al (2003) What does it mean? zri=20+10 -9 (assuming x=nHI/nHtot=0)

  7. 3: Lyaforest:zri < 9-10 Hui & Haiman 2003; Theuns et al 2002 Hui & Haiman (2002)

  8. Solution: Prolonged Reionization Process One viable pre-WMAP physical model: Universe Was Reionized Twice! (Cen 2003a; Wyithe & Loeb 2003)

  9. What could reionize the universe early: More ionizing photons wanted Quasar space density Star formation rate log [n(z) / n(peak)] log [d* /dt/M yr-1 Mpc-3] redshift redshift (Haiman, Abel & Madau 2001) 2 1 ? ? 0 -1 Z Z

  10. IMF for Population III (First) Stars Recent theoretical works suggest a new picture for Pop III IMF (Nakamura & Umemura 2001, 2002;Abel et al 2002; Bromm et al 2002): Pop III IMF may be very top-heavy, possibly with most of the stars with mass >~ 100 Msun Abel et al (2002)

  11. Bromm et al (2002)

  12. Tan & McKee (2002, 2004): The mass of Pop III stars is likely to fall in the range of M = 30-100 Msun due to stellar feedback processes

  13. Observ. Case: Massive Pop III Stars Based on abundance patterns of extremely metal-poor Galactic stars: Oh et al. (2001), Qian & Wasserburg (2002): M>140 Msun PISN with no r-process elements Umeda & Nomoto (2004), Tumlinson, Venkatesan, & Shull (2004): M=10-140Msun Type II supernovae/hypernovae

  14. Ionizing photon emission efficiency Pop III M*=10-300Msun: eUV=40,000-100,000 photons/baryon Salpeter IMF Z=0.01Zsun : eUV=3500 photons/baryon eUV(Pop III) /eUV(Pop II) =10-30 Bromm, Kudritzkl & Loeb (2001)

  15. Existence of double peaks in h h = photon production rate/photon destruction rate = c* fesc (df*/dt) eUV/ C(1+z)3  Double peaks: one @z1~15-30, the other@z2~6-10 • c*: star formation efficiency (unknown) • fesc: ionizing photon escape fraction (unknown) • eUV: ionizing photon production efficiency • df*/dt: halo formation rate (computable) • C: gas clumping factor (constrained)

  16. A closer look: a pre-WMAP model Evolution of neutral hydrogen fraction Recent additional constraints: Wyithe & Loeb (2004): x=a few x 10% @z~6.3 based on QSO Stromgren sphere size Mesinger & Haiman (2004,ApJ): x>=0.2 @z~6.3 based on QSO Stromgren sphere size Haiman & Cen (2005,ApJ): x=<0.25 @z~6.5 based on LAE LF Malhotra & Rhoads (2004,ApJ): x<1 @z~6.5 based on LAE LF White’s talk (2006): x~0.03 based on Stromgren sphere sizes. Totani’s talk (2006): X < 0.6 based on GRB spectra nHI/nHtot & nHII/nHtot XHI=0.1 – 0.3 @z=6-12 t=0.10 +- 0.03 Cen (2003a) Redshift

  17. Evolutionof the mean IGM temperature Mean IGM temperature (K) Redshift

  18. Post-WMAP: implications on Pop III star formation processes • Without Pop III massive stars: te < 0.09 • With Pop III massive stars and reasonable star formation efficiency • and ionizing photon escape fraction: te =0.09---0.12 • With an inefficient metal enrichment process and • Pop III massive stars: te = 0.15 possible • To reach te = 0.17 requires either (1) ns >=1.03 • or (2) c*(H2, III) > 0.01, or (3) photon escape fraction very high for Pop III Cen (2003b)

  19. A more detailed calculation (Wyithe & Cen 2006, astro-ph/0602503) • Separate treatments of halo gas and • IGM in metal enrichment • Follow Pop III/II with a gradual • transition determined by metals • Include photoionization feedback • and minihalo screening effects fcrit/fJeans Redshift

  20. New results from this more detailed calculation (Wyithe & Cen 2006) • Without Pop III massive stars: te < 0.05-0.06, with a rapidly increasing xHI • to >0.5 by z=8 • With Pop III massive stars and reasonable star formation efficiency • and ionizing photon escape fraction: te =0.09---0.12, with an extended • plateau of xHI =0.1-0.3 at z=7-12 • With perhaps too generous assumptions about Pop III star formation • processes (very high escape fraction and/or very high star formation • efficiency), te = 0.21 max is possible. • Which one would I bet on? Physical sanity would eliminate the last choice. • Physical reasonableness for Pop III IMF would then argue for the second • choice. So te =0.09---0.12 seems most likely, same as I got 4 years ago. • Judgement day: Thursday, March 16, 2006 (3rd Yr WMAP results)

  21. A 24-billion-particle radiation transfer simulation of detailed cosmological reionization process (Trac & Cen 2006) Particle mass=2x106, Box size=100Mpc/h, timestep determined by c Ncell=120003, Spatial resolution=8kpc comoving

  22. Ok, bets placed, that is all fine! But, How much do you REALLY know about first galaxies?

  23. A 21-cm probe of individual first galaxies using CMB as the background radio source with an antenna temperature of TCMB dT = (Ts-TCMB)(1-e-t) TCMB = 85K, TIGM=18K @z=30

  24. The structure of a first galaxy

  25. Threshold by X-ray Background Heating Number per cubic Mpc Halo Mass

  26. Brightness temperature decrement profile

  27. Fundamental Applications with First Galaxies • Probe IMF, ns, mCDM , … at n(gal)=1.e-6/Mpc3 Dns=0.01 (3s) • Determine Pk: DV=100 Gpc3 within z=28-32 such as baryonic oscillations, etc., without messy astrophysical biases • Alcock-Paczynski (AP) test: assuming each measurement 20% error, with 10,000 galaxies  Dw=0.012 (3s), if WM=0.3 (no error) and k=0

  28. Abundance of 21-cm absorption halos Mean IGM temperature (K) Square arcseconds

  29. Typical low high-z galaxies Theory: MHzG~108-109Msun Observed LAEs at z>6: SFR>40Msun/yr (Hu et al 2003; Kodaira et al 2003), assuming c*=0.10, tsb=5x107yrs ---> MLAE (total) = 1x1011Msun Thus, the current observations of z>6 LAEs do not probe the bulk of first galaxies; typical observed LAEs at z<6 have SFR~a few Msun/yr (Rhoads et al 2003; Taniguchi et al 2003) Cen (2003c)

  30. Quasar Stromgren spheres Cen (2003c) Rs= 4.3x-1/3(N/1.3x1057s-1)1/3(tQ/2x107yr)1/3[(1+zQ)/7.28]-1 Mpc t(r)= 1.2x(WM/0.27)-1(Wb/0.047)[(Rs2-r2sin2q)1/2-r cosq]-1 , where Rs and r are in proper Mpc Cen & Haiman (2000)

  31. Application of high-z galaxies inside quasar Stromgren spheres (1): probing ionization state of IGM and sizes of Stromgren spheres Evidently, (i) x=0.1 and x=0.01 differentiated at >6s level (ii) Rs determined to high accuracy; consequently, tQ determined accurately Rs=3Mpc Cen (2003) x=0.01 0.1 1.0 Rs=5Mpc

  32. Application of first galaxies inside quasar Stromgren spheres, cont. (2) galaxy luminosity function and spatial distributions at z>6 (3) probing environment around quasars (4) probing anisotropy of quasar emission …

  33. Conclusions • The universe has a long reionization process (Wyithe & Cen 2006). • The star formation processes at high-z may be quite different from those for low-z and local star formation • 3rd+…… year WMAP data should give us a lot firmer information

  34. A profitable way to detect high-z galaxies may be to target high-z observed luminous quasars, which provide a set of interesting applications • Radio observations of 21-cm line may provide a unique way to detect the very first galaxies at z=30-40, which could potentially provide a set of fundamental applications.

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