Cosmological Reionization Nick Gnedin

Co-starring Gayler Harford Katharina Kohler Peter Shaver Mike Shull Massimo Ricotti

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

The Brief History of Time Today: z=0 t=13.7 Gyr End of inflation: z=10 27 t= s Recombination: z=1089 t=379 kyr ionized neutralionized RE-IONIZATION

All You Need to Know About the Lyman-alpha Forest Lyman-alpha emission line Intrinsic QSO spectrum Absorbed fluxTransmitted flux

What We Know About Reionization Ly-  Ly- 

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

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

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

Star Formation Schmidt Law: Parameters: star formation efficiency  SF UV emission efficiency  UV ( =E UV /M * c 2 )

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

How It All Happens…

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

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

Redshift of Overlap z REI = (2  )

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 …

SLOAN quasars

Lyman-Break Galaxies Observed LB galaxiesSimulated galaxies L Observations Simulations

Dwarf Galaxies Real dwarfs Virtual dwarfs

Star Formation

Metallicity

Kinematics

But  = 0.17  = 0.06  = 0.17

But… (as of Oct 2003)  =17+4%  =12+6%  =10+6%  Polarization Temperature Galaxy clustering

Conclusions I Reionization proceeds in 3 stages: In the pre-overlap stage more-or-less isolated H II regions expand into the neutral IGM (bubbles of ionized gas in the sea of neutral gas). Measurement of high  indicates that new physics was present in this stage. During the overlap isolated HII regions merge together (looks like a mess). It happened at z REI = 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).

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.

The End

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