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

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

Hubble Space Telescope Realm of the Galaxies

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

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

Gnedin 03 Reionization: the movie 8Mpc comoving

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

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

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

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)

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

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

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

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

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

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

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 Mpc

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

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

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

All sky: SI deviations = 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

 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

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

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

Destination: Moon!

GMRT 230 MHz – HI 21cm abs toward highest z radio galaxy, 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 +

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

Constraint III: Cosmic Stromgren Spheres : 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