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Cosmic Dawn and IGM Reionization

Cosmic Dawn and IGM Reionization. Andrea Ferrara. SISSA/International School for Advanced Studies, Trieste. At z=1000 the Universe has cooled down to 3000 K. Hydrogen becomes neutral (“ Recombination ”). At z < 20 the first “ PopIII ” star (clusters)/small galaxies form.

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Cosmic Dawn and IGM Reionization

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  1. Cosmic Dawn and IGM Reionization Andrea Ferrara SISSA/International School for Advanced Studies, Trieste

  2. At z=1000 the Universe has cooled down to 3000 K. Hydrogen becomes neutral (“Recombination”). At z < 20 the first “PopIII” star (clusters)/small galaxies form. At z ~ 6-15 these gradually photo-ionize the hydrogen in the IGM (“Reionization”). At z<6 galaxies form most of their stars and grow by merging. At z<1 massive galaxy clusters are assembled. Sequenceof Events Cosmic Dawn Time

  3. Envelope: 103 Mo Core:10-2 Mo Infall Rate: 0.01Mo/yr temperature density

  4. ~ (1+zend ) λLyα First Light at Cosmic Dawn: Very Massive Stars Salvaterra& AF 2002; Magliocchetti, Salvaterra & AF 2003 IR Background Data Points Best fit model to NIR data zend = 8.8 f 30% PopIII Stars+Galaxies Galaxies Pop III stars can explain observed NIRB excess if VMS dominate IMF

  5. Reionization by Very Massive Stars ? z = 17 NIRB - fitting evolution

  6. Reionization Tests WMAP results: reionization at z>10 ? Temperature-Polarization Cross Power Spectrum τe = 0.17± 0.04

  7. Inhomogeneous Reionization Choudhury & AF 2005 • Self-consistent treatment of the evolution of ionized regions and thermal history • Follow evolution of neutral, HII and HeIII regions; treat IGM as multiphase gas • Inhomogeneous density distribution: log-normal model • Three sources of ionizing radiation: PopIII stars: early redshifts, high mass, zero metallicity PopII stars: Salpeter IMF, transition from PopIII @ z < 9 Quasars: significant @ z < 6, using -MBH relation • Radiative feedback suppressing SF in low-mass halos, set by:  Molecular cooling in neutral regions  Photoionization temperature in ionized regions

  8. HI Photo-rates HeII GP optical depth e.s. optical depth Experimental constraints Ionized regions filling factor Mean density temperature LLS statistics log

  9. late reionization early reionization (T/T0)CMB (Tb/T0)21CM Inhomogeneous Reionization Salvaterra, Ciardi, AF & Baccigalupi 2005 Additional hints from CMB+21cm line CROSS CORRELATE 115 MHz 90 MHz

  10. Inhomogeneous Reionization Salvaterra, Ciardi, AF & Baccigalupi 2005 HII regions: size evolution Size of HII region (Mpc) from zero of correlation fct. early late Bandwidth

  11. The UVB in the Post-Reionization Epoch Miniati, AF, White & Bianchi 2004 Ionizing photons from structure formation QSOs Thermal Galaxies  Mass range: log M = 11 – 13  Virial temperatures: log T  6  Bremsstrahlung + line emission  Escape fraction  1

  12. The UVB in the Post-Reionization Epoch Miniati et al 2004 Ionizing photons from structure formation HI HeII Total Fan 2002 Thermal QSOs QSOs Galaxies Galaxies Thermal Thermal, no feedback Thermal, no feedback Photoionization rates

  13. HI HeII Photoionization rates fluctuations through a box at z=3.27 Radiative Transfer Effects on the Ly Forest Maselli & AF, in prep UVB fluctuations See Maselli’s poster  Power spectrum  Temperature  Elemental abundances  Eta parameter Affects:

  14. Brief Summary • Massive first stars likely responsible for NIRB excess can reionize the IGM at z15 • Early reionization not in contrast with any constraint from QSO absorption line data • Detailed reionization history from coupled CMB/21cm experiments • HeII reionization more complex; affected by thermal radiation from structure formation • Photoionization rate fluctuations (10%, 60%) for (HI, HeII) induced by RT effects

  15. Want to know more ?

  16. THE END

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