1. Open Discussion 1 KIAA/PKU Reionization
C. Carilli (facilitator), July 2008
Ionized f(HI) ~ 0
Neutral f(HI) ~ 1
Djorgovski + digital media center, CIT
Reionized f(HI) ~ 1e-5

2. Taking stock Was the IGM substantially ionized (>50%) at z~20?
Was the IGM partially neutral (>10%) at z~7?
Was the Universe ionized by
Big galaxies
Small galaxies
Luminous quasars
Mini-quasars
Other
Is there any evidence for (massive) Pop III stars?
Is the MBH -- Mspheriod relation observationally unassailable, and if so, what is the physical origin?
Is GP effect simply a thickening of Lya forest (does it matter, physically)?
What is the largest bubble expected in 30o x 30o x (z=14 to 7)?

3. Taking stock
Was the IGM substantially ionized (>50%) at z~20? (No - CMBpol)
Was the IGM partially neutral (>10%) at z~7?
Was the Universe ionized by
Big galaxies
Small galaxies
Luminous quasars (No, SDSS)
Mini-quasars
Other
Is there any evidence for (massive) Pop III stars?
Is the MBH -- Mspheriod relation observationally unassailable, and if so, what is the physical origin?
Is GP effect simply a thickening of Lya forest (does it matter, physically)?
What is the largest bubble expected in 30o x 30o x (z=14 to 7)?

4. Rules-out high ionization fraction at z> 15
Constraint II: CMB large scale polarization -- Thomson scattering during reionization
Rules-out high ionization fraction at z> 15
Allows for finite (~0.2) ionization to high z
Most action occurs at z ~ 8 to 14
Is this evidence irrefutable (cf. Galacic FG), and is it relevant at z~7? ?
Dunkley et al. 2008

5. Not ‘event’ but complex process, large variance: zreion ~ 6 to 14 OI
Not ‘event’ but complex process, large variance: zreion ~ 6 to 14
Good evidence for qualitative change in nature of IGM at z~6
ESO

6. Current probes are all fundamentally limited in diagnostic power OI
Saturates, HI distribution function, pre-ionization?
Abundance?
Integral measure?
Local ionization?
Geometry, pre-reionization?
Local ioniz.?
Current probes are all fundamentally limited in diagnostic power
Need more direct probe of process of reionization = HI 21cm line

7. Gunn-Peterson Effect toward z~6 SDSS QSOs
Fan et al 2006
Is GP absorption fundamentally different than thickening of the Lya forest?