Cosmic reionization and the history of the neutral intergalactic medium LANL Chris Carilli May 23, 2007  Current constraints on the IGM neutral fraction with cosmic epoch (Fan, Carilli, Keating 2006 ARAA)  Neutral Intergalactic Medium (IGM) – HI 21cm telescopes, signals, and challenges  Objects within reionization – recent observations of molecular gas, dust, and star formation, in the host galaxies of the most distant QSOs, and more…

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 Twilight Zone Epoch of Reionization Last phase of cosmic evolution to be tested Bench-mark in cosmic structure formation indicating the first luminous structures

Gnedin 03 Reionization: the movie 8Mpc comoving

Barkana and Loeb 2001 Constraint I: Gunn-Peterson Effect z

Gunn-Peterson Effect Fan et al 2006

Gunn-Peterson limits to f(HI) End of reionization? f(HI) <1e-4 at z= 5.7 f(HI) >1e-3 at z= 6.3 Difficulties with GP  to f(HI) conversion requires ‘clumping factor’  >>1 for f(HI)>0.001 => low f(  ) diagnostic GP => Reionization occurs in ‘twilight zone’, opaque for obs <0.9  m  GP = 2.6e4 f(HI) (1+z)^3/2

Reionization and the CMB Thomson scatting during reionization (z~10)  Acoustics peaks are ‘fuzzed-out’ during reionization.  Problem: degenerate with intrinsic amplitude of the anisotropies. Surface of last-scattering z~1000 No reionization Reionization CMB angular power spectrum

TT TE EE Constraint II: CMB large scale polarization -- Thomson scattering during reionization   Scattered CMB quadrapole => polarized   Large scale: horizon scale at reionization ~ 10’s deg  Signal is weak: TE = 10% TT (few uK) EE = 1% TT  EE (l ~ 5)~ 0.3+/- 0.1 uK Page + 06; Spergel 06

TT TE EE Constraint II: CMB large scale polarization -- Thomson scattering during reionization    e = 0.09+/-0.03  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, with f(HI) < 0.5 Page + 06; Spergel 06

 es with CMB polarization:  e = integral measure to recombination=> allows many IGM histories Still a 3  result (now in EE vs. TE before) Combined CMB + GP constraints on reionization

Highest redshift quasar known (t univ = 0.87Gyr) L bol = 1e14 L o Black hole: ~3 x 10 9 M o ( Willot etal. ) Gunn Peterson trough (Fan etal.) Pushing into reionization: QSO at z=6.4

z=6.42: Gas detection Off channels Rms=60uJy GHz CO 3-2 M(H 2 ) ~ 2e10 M o z host = / (note: z ly  = /- 0.04) VLA IRAM VLA

Constrain III: Cosmic Stromgren Sphere Accurate z host from CO: z=6.419+/0.001 Proximity effect: photons leaking from 6.32<z<6.419 z=6.32 ‘time bounded’ Stromgren sphere: R = 4.7 Mpc t qso = 1e5 R^3 f(HI)~ 1e7yrs or f(HI) ~ 1 (t qso /1e7 yr) White et al. 2003

Loeb & Rybicki 2000

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

Cosmic Stromgren Surfaces (Hui & Haiman) Larger CSS in Ly  vs. Ly  = Damping wing of Ly  ? Large N(HI) => f(HI) > 0.1 z host

Difficulties for Cosmic Stromgren Spheres and Surfaces (Lidz + 07, Maselli + 07)  Requires sensitive spectra in difficult near-IR band  Sensitive to R: f(HI)  R^-3  Clumpy IGM => ragged edges  Pre-QSO reionization due to star forming galaxies, early AGN activity

Cosmic ‘phase transition’?  Not ‘event’ but complex process, large variance time/space  Current observations suggest: z reion ~ 6 to 14  Good evidence for qualitative change in nature of IGM at z~6  Current probes are all fundamentally limited in diagnostic power

Studying the pristine neutral IGM using redshifted HI 21cm observations (100 – 200 MHz) Large scale structure  cosmic density,   neutral fraction, f(HI)  Temp: T K, T CMB, T spin 1e13 M o 1e9 M o

Multiple experiments under-way: ‘pathfinders’ MWA (MIT/CfA/ANU) LOFAR (NL) 21CMA (China) SKA

Signal I: Global (‘all sky’) reionization signature in low frequency HI spectra Ly  coupling: T spin =T K < T CMB IGM heating: T spin = T K > T CMB Gnedin & Shaver MHz Signal ~ 20mK < 1e-4 sky

EDGES (Bowman & Rogers MIT) All sky reionization HI experiment. Single broadband dipole experiment with (very) carefully controlled systematics + polynomial baseline subtraction (7th order)  T reion < 450mK at z = 6.5 to 10 Sky > 150 K rms = 75 mK VaTech Dipole Ellingson

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

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

N(HI) = 1e13 – 1e15 cm^-2, f(HI/HII) = 1e e-6 => Before reionization N(HI) =1e18 – 1e21 cm^-2 Signal IV: 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 Perhaps easiest to detect (use long baselines) Requires radio sources: expect 0.05 to 0.5 deg^-2 at z> 6 with S 151 > 6 mJy? 159MHz

GMRT 230 MHz – HI 21cm abs toward highest z (~5.2) radio AGN z=5.2 S 230MHz = 0.5 Jy 1” 8GHz Van Breugel et al. GMRT at 230 MHz = z 21cm RFI = 20 kiloJy ! CO Klamer + M(H 2 ) ~ 3e10 M o

GMRT 230 MHz – HI 21cm abs toward highest z radio AGN (z~5.2) rms(20km/s) = 5 mJy 229Mhz 0.5 Jy 232MHz 30mJy rms(40km/s) = 3mJy N(HI) ~ 2e20T S cm^-2 ?

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 Very low frequency (<75MHz)= Long Wavelength Array Very difficult to detect  Signal: 10 arcmin, 10mk => S 30MHz = 0.02 mJy  SKA sens in 1000hrs: = 20000K at 50MHz => rms = 0.2 mJy  Need > 10 SKAs  Need DNR > 1e6 z=50 z=150 Barkana & Loeb 2005

Challenge I: Low frequency foreground – hot, confused sky Eberg 408 MHz Image (Haslam ) 90% = Galactic foreground. Coldest regions: T ~ 100  z)^-2.6 K 10% = Egal. radio sources = 1 source/deg^2 with S 140 > 1 Jy

Solution: spectral decomposition (eg. Morales, Gnedin…)  Foreground = non-thermal = featureless over ~ 100 MHz  Signal = fine scale structure on scales ~ few MHz 10’ FoV; SKA 1000hrs Xcorrelation/Power spectral analysis in 3D – different symmetries in freq space Freq Signal Foreground Signal/Sky ~ 2e-5

 ‘Isoplanatic patch’ = few deg = few km  Phase variation proportional to wavelength^2 74MHz Lane 03 Challenge II: Ionospheric phase errors – varying e- content TID

Solution: Wide field ‘rubber screen’ phase self- calibration = ‘peeling’ Virgo A VLA 74 MHz Lane ’ Ionospheric phase errors: The Movie

Challenge III: Interference 100 MHz z= MHz z=6 Solutions -- RFI Mitigation (Ellingson06)  Digital filtering: multi-bit sampling for high dynamic range (>50dB)  Beam nulling/Real-time ‘reference beam’  LOCATION!

Beam nulling -- ASTRON/Dwingeloo (van Ardenne) Factor 300 reduction in power

VLA-VHF: 180 – 200 MHz Prime focus CSS search Greenhill, Blundell (SAO); Carilli, Perley (NRAO) Leverage: existing telescopes, IF, correlator, operations  $110K D+D/construction (CfA)  First light: Feb 16, 05  Four element interferometry: May 05  First limits: Winter 06/07

Project abandoned: Digital TV KNMD Ch 9 150W at 100km

RFI mitigation: location, location location… 100 people km^-2 1 km^ km^-2 (Briggs 2005)

Challenge IV: Extreme computing LOFAR: IBM Blue Gene/L “Stella” (Falcke) 0.5 Tbit/s input data rate 30 Tflop ~ PCs Occupying 6 m KW power consumption ~1.7% slower than #1 in Europe (Barcelona) … Dutch minister of science Blue Gene

Focus: Reionization (power spec,CSS,abs)

PAPER: Staged Engineering Approach Broad band sleeve dipole => 2x2 tile 8 dipole test array in GB (06/07) => 64 station array in WA (07/08) FPGA-based ‘pocket correlator’ from Berkeley wireless lab => custom design. BEE2: 5 FPGAs, 500 Gops/s S/W Imaging, calibration, PS analysis: Miriad => Python + CASA, including ionospheric ‘peeling’ calibration + MFS ‘Peel the problem onion’ 100MHz200MHz

PAPER: First images/spectra Cygnus A 1e4Jy Cas A 1e4Jy 3C Jy 3C Jy 140MHz 180MHz CygA 1e4Jy

Destination: Moon! RAE  No interference  No ionosphere (?)  Easy to deploy and maintain (high tolerance electroncs + no moving parts) 10MHz

Radio astronomy – Probing Cosmic Reionization ‘Twilight zone’: study of first light limited to near-IR to radio 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

European Aeronautic Defence and Space Corporation/ASTRON (Falcke) Payload = 1000 kg (Ariane V) 100 antennas at 1-10 MHz ~ 1/10 SKA

END

IPS/ISS angular/temporal broadening: 1MHz => 1deg, 5years Faraday rotation => no linear polarization High sky temperature Low power super computing: LOFAR/Blue Gene = 0.15MW Lunar ionosphere: p = 0.2 to 1MHz (LUNA19, ’s)? Diffraction limits: how sharp is knife’s edge? Very low frequencies (<10MHz): Lunar challenges

ARTICLE 22 (ITU Radio Regulations) Space services Section V – Radio astronomy in the shielded zone of the Moon 22.22§ 81)In the shielded zone of the Moon 31 emissions causing harmful inter­ference to radio astronomy observations 32 and to other users of passive services shall be prohibited in the entire frequency spectrum except in the following bands: a)the frequency bands allocated to the space research service using active sensors; 22.24b)the frequency bands allocated to the space operation service, the Earth exploration-satellite service using active sensors, and the radiolocation service using stations on spaceborne platforms, which are required for the support of space research, as well as for radiocommunications and space research transmissions within the lunar shielded zone )In frequency bands in which emissions are not prohibited by Nos to 22.24, radio astronomy observations and passive space research in the shielded zone of the Moon may be protected from harmful interference by agreement between administrations concerned The shielded zone of the Moon comprises the area of the Moon’s surface and an adjacent volume of space which are shielded from emissions originating within a distance of km from the centre of the Earth The level of harmful interference is determined by agreement between the administrations concerned, with the guidance of the relevant ITU-R Recommendations. Good “news” … The Moon is radio protected! The back side of the moon is declared as a radio protected site within the ITU Radio Regulations –The IT Radio Regulations are an international treaty within the UN. –Details are specified in a published ITU Recommendation (this is a non-mandatory recommendation, but is typically adhered to).  Radio astronomy on the moon has been a long-standing goal, protected by international treaties!  Steps need to be taken to protect the pristine and clean nature of the moon.  Lunar communication on the far side needs to be radio quiet.

Sources responsible for reionization  Luminous AGN: No  Star forming galaxies: maybe -- dwarf galaxies (Bowens05; Yan04)?  mini-QSOs -- unlikely (soft Xray BG; Dijkstra04)  Decaying sterile neutrinos -- unlikely (various BGs; Mapelli05)  Pop III stars z>10? midIR BG (Kashlinsky05), but t recomb < t univ at z~10 GP => Reionization occurs in ‘twilight zone’, opaque for obs <0.9  m Needed for reion.

Radio galaxy spectra: Smooth powerlaw (eg. Cygnus A)

Tsiolkovsky crater (100 km diameter) 20°S 129°E Apollo 15 Tsiolkovsky crater