1. HI 21cm Tomography of IGM: freq ~ 100 to 200 MHz
Furlanetto, Zaldarriaga
z=12 9
Large scale structure: , f(HI) , Temp (K, CMB, Spin)
Advantages: 3D, optically thin, dominant baryon component
Tomography requires SKA
TB(2’) = 10’s mK
SKA rms(100hr) = 4mK
LOFAR rms (1000hr) = 80mK
0.5Mpc
7.6

2. Challenge: Low frequency foreground – hot, confused sky
Eberg 408 MHz Image (Haslam )
0.5 to 5.0 GHz
Coldest regions: T ~ 100 (/200 MHz)^-2.6 K
Highly ‘confused’: 1 source/deg^2 with S140 > 1 Jy
Synch. smooth ~ 100MHz vs. 21cm lines ~ 1 MHz

3. Chromatic aberration: Frequency differencing with MHz channels doesn’t work well due to frequency dependent far-out sidelobes
142, 174 MHz

5. Simulation: effects of residual calibration errors
6C source counts > 1Jy (Smax = 200 Jy)

6. UVSUB ~ ‘real-time’ source removal
IMLIN ~ post-processing freq fitting (3rd order)

7. Datta+ 09
0.1% 1%
For errors constant over 1 day: DNR requirement ~ 0.2% calibration errors

8. Datta + Bowman in prep
300 hours
0.1% calibration errors

9. Cosmic Stromgren Sphere
Accurate host redshift from CO: z=6.419+/0.001
Ly a, high ioniz lines: inaccurate redshifts (z > 0.03)
Proximity effect: photons leaking from 6.32<z<6.419
White et al. 2003
z=6.32
‘time bounded’ Stromgren sphere: R = 4.7 Mpc
tqso = 1e5 R^3 f(HI)~ 1e7yrs or
f(HI) ~ 1 (tqso/1e7 yr)

10. Loeb & Rybicki 2000

11. CSS: Constraints on neutral fraction at z~6
Nine z~6 QSOs with CO or MgII redshifts: <R> = 4.4 Mpc (Wyithe et al. 05; Fan et al. 06; Kurk et al. 07)
GP => f(HI) > 0.001
If f(HI) ~ 0.001, then <tqso> ~ 1e4 yrs – implausibly short given QSO fiducial lifetimes (~1e7 years)?
Probability arguments + size evolution suggest: f(HI) > 0.05
Wyithe et al. 2005
Fan et al 2006
P(>xHI)
90% probability
x(HI) > curve
=tqso/4e7 yrs