1. HI 21cm Signal from Cosmic Reionization IAU 2006, Long Wavelength Astrophysics Chris Carilli (NRAO) Ionized Neutral Reionized

2. Chris Carilli (NRAO) Berlin June 29, 2005 WMAP – structure from the big bang

3. Hubble Space Telescope Realm of the Galaxies

4. Dark Ages Age of Enlightenment Epoch of Reionization last phase of cosmic evolution to be tested bench-mark in cosmic structure formation indicating the first luminous structures

5. HI 21cm observations of Cosmic Reionization, and beyond  Most direct probe of epoch and process of reionization  Rich in physical diagnostics  Only probe of cosmic evolution during ‘dark ages’ TALK:  Current observational constraints on reionization (Fan et al. ARAA 2006)  Predicted HI 21cm signals  Telescopes and Challenges

6. Gnedin 03 Reionization: the movie 8Mpc comoving

7. Constraint I: Gunn-Peterson Effect Fan et al 2006 End of reionization? f(HI) > 1e-3 at z = 6.3 vs. <1e-4 at z= 5.7

8. Fan et al 2003 TT TE EE Constraint II: CMB large scale polarization: Thompson scattering during reionization   Scattered CMBquad. => polarized   Horizon scale => 10’s deg   = 0.09+/-0.03 => z _reion = 11+/3 Page + 06

9. Current observations => z_reion = 6 to 11?  Not ‘event’ but complex process, large variance time/space  GP => occurs in ‘twilight zone’, opaque _obs  < 0.9  m

10. Limitations of current measurements: CMB polarization  _e = integral measure through universe => allows many reionization scenarios Still a 3  result (now in EE vs. TE before) Gunn-Peterson effect  _Lya >>1 for f(HI)>0.001 => low f  diagnostic  to f(HI) conversion requires ‘clumping factor’ (cf. Becker, Rauch, Sargent 2006)

11. Studying the pristine IGM into the EOR using redshifted HI 21cm observations (100 – 200 MHz) Large scale structure:  cosmic density,   neutral fraction, f(HI)  Temp: T _K, T _CMB, T _spin  Heating: Ly , Xrays, shocks

12. Signal I: Global (‘all sky’) reionization signature in low frequency HI spectra 21cm ‘deviations’ < 1e-4 wrt foreground Lya coupling: T _spin =T _K < T _CMB IGM heating: T _spin =T _K > T _CMB Gnedin & Shaver 03

13. Signal II: 3D Power spectrum analysis SKA LOFAR McQuinn + 06  only  + f(HI)

14. Signal III: HI 21cm Tomography of IGM Zaldarriaga + 2003 z=1297.6   T _B (2’) = 10’s mK  SKA rms(100hr) = 4mK  LOFAR rms (1000hr) = 80mK

15. N(HI) = 1e13 – 1e15 cm^-2, f(HI/HII) = 1e-5 -- 1e-6 => Before reionization N(HI) =1e18 – 1e21 cm^-2 Cosmic Web after reionization Ly alpha forest at z=3.6 (  < 10) Womble 96

16. z=12z=8 19mJy 130MHz radio G-P (  =1%) 21 Forest (10%) mini-halos (10%) primordial disks (100%) Signal IV: Cosmic web before reionization: HI 21Forest expect 0.05 to 0.5 deg^-2 at z> 6 with S _151 > 6 mJy

17. Signal V: Cosmic Stromgren spheres around z > 6 QSOs 0.5 mJy  LOFAR ‘observation’: 20xf(HI)mK, 15’,1000km/s => 0.5 x f(HI) mJy  Pathfinders: Set first hard limits on f(HI) at end of cosmic reionization  Easily rule-out cold IGM (T _s < T _cmb ): signal = 360 mK Wyithe et al. 2006 5Mpc

18. Signal VI: pre-reionization HI signal eg. Baryon Oscillations (Barkana & Loeb) Very difficult to detect !  z=50 => = 30 MHz  Signal: 30 arcmin, 50 mk => S _30MHz = 0.1 mJy  SKA sens in 1000hrs: T _fg = 20000K => rms = 0.2 mJy z=50 z=150

19. ‘Pathfinders’: PAST, LOFAR, MWA, PAPER, … MWA (MIT/ANU) LOFAR (NL) PAST (CMU/China) PAPER Berk/NRAO

21. Challenge I: Low frequency foreground – hot, confused sky Eberg 408 MHz Image (Haslam + 1982) Coldest regions: T = 100  z)^-2.6 K Highly ‘confused’: 1 source/deg^2 with S _0.14 > 1 Jy

22. All sky: SI deviations = 0.001 Solution: spectral decomposition (eg. Morales, Gnedin…) 10’ FoV; SKA 1000hrs Power spectral analysis: Fourier analysis in 3D – different symmetries in freq space ( ie. Different spectral chan-chan correlation) Freq SignalForeground

23.  TIDs – ‘fuzz-out’ sources  ‘Isoplanatic patch’ = few deg = few km  Phase variation proportional to ^2 Solution: Wide field ‘rubber screen’ phase self- calibration Challenge II: Ionospheric phase errors – varying e- content Virgo A VLA 74 MHz Lane + 02

24. Challenge III: Interference 100 MHz z=13 200 MHz z=6 KNMD Ch 9 Digital TV Solutions: RFI Mitigation  Digital filtering  Beam nulling  Real-time ‘reference beam’

25. Solution – RFI mitigation: location, location location… 100 people km^-2 1 km^-2 0.01 km^-2

26. Destination: Moon!

27. GMRT 230 MHz – HI 21cm abs toward highest z radio galaxy, 0924-220 z=5.2 rms(20km/s) = 5 mJy z(CO) 230Mhz 0.5 Jy 8GHz 1” Van Breugel et al. RFI = 20 kiloJy ! CO Klamer +

28. Radio astronomy – Probing Cosmic Reionization ‘Twilight zone’: study of first light limited to near- IR to radio ’s First constraints: GP, CMBpol => reionization is complex and extended: z _reion = 6 to 11 HI 21cm: most direct probe of reionization Low freq pathfinders: All-sky, PS, CSS SKA: imaging of IGM

29. Constraint III: Cosmic Stromgren Spheres 1148+5251: Accurate z _host from CO: z=6.419+/0.001 Proximity effect: photons leaking from 6.32<z<6.419 ‘time bounded’ Stromgren sphere: R = 4.7 Mpc f(HI) = 1e-5 R^-3 (t _qso /1e7) yrs ~ 0.1 for sample 19 QSOs at z>5.7 (Fan et al. 06; Wyithe et al. 04) White et al. 2003