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Cosmological Reionization

Cosmological Reionization. Nick Gnedin. Outline. The brief history of time What we know about reionization Reionization: ABC Data vs theory Conclusions. End of inflation: z=10 27 t=10 -36 s. Recombination: z=1089 t=379 kyr. Today: z=0 t=13.7 Gyr. neutral. ionized. ionized.

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Cosmological Reionization

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  1. Cosmological Reionization Nick Gnedin

  2. Outline The brief history of time What we know about reionization Reionization: ABC Data vs theory Conclusions

  3. End of inflation: z=1027 t=10-36s Recombination: z=1089 t=379 kyr Today: z=0 t=13.7 Gyr neutral ionized ionized RE-IONIZATION The Brief History of Time

  4. Ly-b Ly-a What We Know About Reionization

  5. What We Know About Reionization: A or B? “…the universe is approaching the reionization epoch at z~6” (Becker et al. 2001) Sloan quasars Fraction of flux transmitted

  6. That’s the key! Simulations • dark matter dynamics • gas dynamics • star formation • metal cooling • exact physics of primeval plasma • fine print (secondary electrons, Ly-a pumping, …) • radiative transfer ^ the only phenomenology! Note: non-existing things are not included

  7. WMAP Cosmological Parameters 2003 Baryons: 4% Dark matter: 23% Dark energy: 73% …

  8. Neutral hydrogen HII regions Galaxies How It All Happens… 4 chimps

  9. How It All Happens…

  10. How It All Happens: ABC Pre-overlap: HII regions expand in the low density gas. Overlap: HII regions merge – the moment of reionization. Post-overlap:High density regions are being ionized from the outsize.

  11. Pre-overlap Overlap Post-overlap “A redshift of reionization” Redshift of Overlap

  12. zREI=6.1 + 0.3 (2s) Redshift of Overlap

  13. WMAP model • Individual spectra of bright quasars are very similar to that of SLOAN quasars. • Large galaxies at z~4 have colors identical to observed Lyman Break Galaxies. • Star formation rate is consistent with observational measurements at z~4. • Smallest galaxies formed in the simulation look like dwarf spheroidals in all their properties, including abundance (no satellite problem). • Lyman-alpha forest (including metal absorption systems) is consistent with observations. • but …

  14. SLOAN quasars

  15. Lyman-Break Galaxies Observed LB galaxies Simulated galaxies L Observations Simulations

  16. Dwarf Galaxies Real dwarfs Virtual dwarfs

  17. Star Formation

  18. Metallicity

  19. Kinematics

  20. But t = 0.06 t = 0.17 t = 0.17

  21. Conclusions I • Reionization proceeds in 3 stages: • In the pre-overlap stage more-or-less isolated HII regions • expand into the neutral IGM (bubbles of ionized gas in the • sea of neutral gas). Measurement of high t indicates that • new physics was present in this stage. • During the overlap isolated HII regions merge together • (looks like a mess). It happened at zREI = 6.1 + 0.3. • In the post-overlap stage the remains of the neutral gas • are being ionized from the outside – most of them become • Lyman-limit systems (bubbles of neutral gas in the sea of • ionized gas).

  22. Conclusions II • Our theoretical models reach the stage when we are able • to make a quantitative comparison between theory and all • existing observational data. • Future observations will be matched by the adequate • progress in our abilities to model formation of early • galaxies and supermassive black holes. • If this decade is a decade of CMB in astronomy, the next • one will be a decade of reionization.

  23. The End

  24. Title

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