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Detecting the first light

Detecting the first light. Han Jiaxin USTC,2007. http://2dark.org. Reionization. last scattering and CMB (300kyr,z~1100) Dark age reionisation(1Gyr,z~6) from first stars structure formation and expansion till present. Expanding and cooling…. Reionization Phases. UV reionization

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Detecting the first light

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  1. Detecting the first light Han Jiaxin USTC,2007 http://2dark.org

  2. Reionization • last scattering and CMB (300kyr,z~1100) • Dark age • reionisation(1Gyr,z~6) from first stars • structure formation and expansion till present Expanding and cooling…

  3. Reionization Phases • UV reionization • StrÖmgren sphere • Percolation / overlap • Etching away • Open questions: • Single epoch vs. Multiepoch (galaxy feedback,SF efficiency…) • Inside-out vs. Outside-in • Reionization sources:X-ray,decaying particle…

  4. Methods of Observation • Lyα absorption • Cosmic StrÖmgren Spheres • Metal lines • GRB • CMB polarization and anisotropy • 21cm line

  5. Lyα absorption • Lyα resonance absorption(1215.67A) UV • Continuous absorption at different z: Gun-Peterson trough • (Gun-Peterson 1965)

  6. Z<5: Lyman alpha forest (fluctuating GP effect) Z>5: overlap of lines, strong evolution Z>6: complete trough, τ>>1, Fallback: saturation Zem= 3.62 QSO1422C23 (V = 16.5) (Keck)

  7. Gun-Peterson Test z~6: • Dramatic decrease in transmitted flux • Increase in optical depth • Lya+Lyb+Lyr : phase transition

  8. Comparison with Simulations: overlap-postoverlap

  9. CMB Probes • Rescattering at Reionization • Sensitive to Ionized fraction • Testing Observables: • Large scale Polarization • Small scale anisotropy

  10. CMB Probe:Polarization • τ-A degeneracy • Polarization: Low-l EE peak (larger horizon than recombination) • Not contaminated by ISW • Future Observertions: Percent level constraints on partial reionization

  11. CMB Probe:Polarization

  12. CMB Probe: B-mode pol • New low-l BB peak • Gravitational lensing: E-->B • More Stringent constraints on GW

  13. CMB Probe: Anisotropy • Patchy Reionization • Secondary effects: • Ostriker-Vishniac effect: Baryon Inhomogeneity Electron Inhomogeneity • Kinetic SZ

  14. CMB Probe: kSZ • PGM Bulk velocitykSZ • Silk dampingtSZ domination at <4’ • tSZ null(217GHz) Te=10keV,y=10-4,Vpec=500km/s

  15. CMB Probe:Anisotropy • Small scales (<0.1deg,l>2000) • Amplitude: duration of patchy phase • No detection yet

  16. 21cm • Direct measurement, 3D image • No saturation

  17. 21cm:Basics • Frequency:1420.4MHz,(200~9)MHz after redshift • Brightness Temperature

  18. 21cm: Interplay with CMB • Z>200: • Thompson scattering, collision • TCMB=Tk=Ts, TB=0 • Z:30~200 • Tk~1/(1+z)2,TCMB~1/(1+z) • TCMB>Tk=Ts, TB<0 • Z:20~30 • Local coupling by Lya, Local IGM warming by X-ray • TB<0, TB=0, TB>0 regions • Z:6~20 • Global IGM warming by first galaxy, BH • Likely TCMB<Tk, TB>0

  19. 21cm:Observation Z=12 Z=7 Z=9

  20. 21cm:Observation Solid: density domination Dotted: with reionization Blue: SKA sensitivity Red: LOFAR sensitivity

  21. 21cm:Observational Challenges • Foregrounds • Ionosphere • Interference

  22. Summary

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