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Epoch of Reionization

Cosmic reionization and other lunar radio studies Chris Carilli (NRAO). Epoch of Reionization. last phase of cosmic evolution to be explored bench-mark in cosmic structure formation indicating the first luminous structures. First observational constraints on cosmic reionization.

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Epoch of Reionization

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  1. Cosmic reionization and other lunar radio studies Chris Carilli (NRAO) Epoch of Reionization • last phase of cosmic evolution to be explored • bench-mark in cosmic • structure formation • indicating the first • luminous structures

  2. First observational constraints on cosmic reionization z=5.80 z=5.82 z=5.99 z=6.28 Gunn-Peterson Effect: zEoR >= 6 Large scale CMB pol: zEoR=11+/-3 TT TE EE T Page Fan

  3. Current observations: zEoR = 14 to 6 (Fan, Carilli, Keating 2006) • Not ‘event’, but complex process, large variance time/space • GP => occurs in ‘twilight zone’, opaque _obs< 0.9 um • Limited Diagnostics • GP: tLya > 1e4 for f(HI)> 1e-3 => low f(HI) • CMB pol = integral measure of te => high f(HI)

  4. Studying the pristine IGM into the EOR, and beyond: redshifted HI 21cm observations in range 30 – 200 MHz SKA goal: mJy at 200 MHz Large scale structure: density, f(HI), T_spin 1e12Mo 1e9Mo

  5. Lunar Advantage I: Interference 100 MHz z=13 200 MHz z=6 RAE-2 1973 Destination: Moon!

  6. Lunar Advantage II: Ionospheric phase distortions • Ionospheric Opacity: • np ~1 to 10 MHz • TIDs – ‘fuzz-out’ sources • ‘Isoplanatic patch’ = few deg = few km • Phase variation proportional to n^-2 Solution: ‘Rubber screen’ phase self-calibration Virgo A VLA 74 MHz Lane + 02

  7. Remaining challenge: Low frequency background • Coldest regions: T = 100 (n/200 MHz)^-2.7 K • Highly ‘confused’: 3 sources/arcmin^2 with S_0.2 > 0.1 mJy Eberg 408 MHz Image (Haslam82) Solution: fitting in the spectral domain

  8. HI 21cm Tomography of IGM Zaldarriaga + 2003 z=12 9 7.6 • DT_B(2’) = 10’s mK => DNR > 1e5 • LOFAR rms (1000hr) = 80mK • SKA rms(100hr) = 4mK

  9. Cosmic Web (IGM) after reionization = Ly alpha forest (d <= 10)) 1422+23 z=3.62 Womble 1996 N(HI) = 1e13 -- 1e15 cm^-2, f(HI/HII) = 1e-5 -- 1e-6 => Before reionization N(HI) =1e18 – 1e21 cm^-2

  10. Signal IV: Cosmic web before reionization: HI 21Forest z=8 19mJy z=12 z=12 z=8 130MHz • Radio G-P (t=1%) • 21 Forest (10%) • Mini-halos (10%) • Primordial disks (100%) • Expect 0.05 to 0.5 sources/deg^2 at z> 6 with S_151 > 6 mJy

  11. GMRT 230 MHz – HI 21cm abs toward highest z radio AGN (z = 5.2) RFI = 20 kiloJy ! 0924-2201 8GHz 1” S230 = 0.5Jy; rms (20km/s) = 5 mJy Van Breugel et al. N(HI) < 1e20 (Ts/100) cm^-2 z(CO)

  12. Molecular gas + fine structure lines: J1148+5251 z=6.42 J1148 VLA CO 3-2 tuniv=0.87 Gyr [CII] IRAM 2.5” CO 6-5 1148+5251 • Only direct probe of host galaxy: dust, molecular gas • Coeval starburst/AGN: SFR ~ 1e3 Mo/yr • 2e10 Mo of molecular gas = fuel for star formation • Early enrichment of heavy elements/dust: zsf > 8

  13. 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 White et al. 2003 • ‘time bounded’ Stromgren sphere: R = 4.7 Mpc • f(HI) = 1e-5 R^-3 (tqso/1e7) yrs

  14. Largest ‘bubbles’ at end of reionization Loeb & Rybicki 2000

  15. HI imaging ofCosmic Stromgren spheres around z > 6 QSOs • LOFAR ‘observation’: 0.5 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 5Mpc 0.5 mJy Wyithe et al. 2006

  16. VLA-VHF: 180 – 200 MHz Prime focus X-dipole Greenhill, Blundell (SAO Rx lab); 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

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

  18. Focus: EoR signal (power spec, CSS, abs) • Very wide field: full cross correlation of all dipoles • Staged engineering approach: GB  Mileura07

  19. PAPER: First images/spectra Cas A 1e4Jy 180MHz 140MHz Cygnus A 1e4Jy 3C348 400 Jy 3C392 200Jy

  20. Very low frequency (<30MHz): pre-reionization HI signal  Lunar imperative; eg. Baryon Oscillations (Barkana & Loeb) Very difficult to detect • Signal: 10 arcmin, 10mk =>S_30MHz= 0.02 mJy • SKA sens in 1000hrs: T= 100(n/200 MHz)^-2.7 K = 20000K at 30MHz => rms = 0.2 mJy Need > 10 SKAs Need DNR > 1e6 z=50 z=150

  21. Lunar VLF science: 0.1 to 10 MHz Advantages • Between Earth’s ionospheric cutoff and heliosphere/Galactic free-free cutoff • Blocked from earth auroral emission • RFI Protected ‘volume’ (ITU 22.22 – 22.25) • Easy deployment: Javelins, Roll-out, Rover, Inflatables • Easy maintenance: ‘cheap’, high tolerance electronics, no moving parts

  22. VLF science Coronal Mass Ejections and space weather ‘early warning system’ – passive + remote sensing (Bastian) Extrasolar planetary radio bursts (Lazio) n ~ 1 – 100 MHz S ~ 0.1 – 100 mJy

  23. Array of lunar sensors Cherenkov radiation from neutrinos in lunar regolith Geophones: lunar seismology

  24. Very low frequencies (<10MHz): Lunar challenges • 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: np = 0.2 to 1MHz (LUNA19,20 1970’s)? • Diffraction limits: how sharp is knife’s edge?

  25. Why not? • Cryogenics: need 4K (HeII) for SIS • Power: ALMA = 5-8 MW • ALMA on the moon: Why? • No Troposphere – phase and opacity, eg. 650GHz (350mm): Trx = 125K, t=0.5, Tsky=150K => Same sensitivity with 16 ants vs. 64 • No wind, less gravity: lighter dishes • Stable platform for interferometry

  26. Radio astronomy – Probing Cosmic Reionization • First constraints: GP, CMBpol=> zEoR = 6 to 14 • HI 21cm: most direct probe of reionization • Low freq pathfinders: • All-sky, PS, CSS, Abs. • SKA: imaging of IGM • Lunar advantages: • Interference • No ionosphere • Relatively ‘easy’

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

  28. END

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

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

  31. ‘Pathfinders’: PAST, LOFAR, MWA, VLA-VHF, … MWA prototype (MIT/ANU) LOFAR (NL) PAST (CMU/China) VLA-VHF (CfA/NRAO)

  32. Main Experiment: Cosmic Stromgren spheres around z=6 to 6.5 SDSS QSOs (Wyithe & Loeb 2004) VLA-VHF 190MHz 250hrs 20 f(HI) mK 15’ • VLA spectral/spatial resolution well matched to expected signal: 7’, 1000 km/s • Set first hard limits on f(HI) at end of cosmic reionization (f(HI) < 0.3) • Easily rule-out cold IGM (T_s < T_cmb): signal = 360 mK 0.50+/-0.12 mJy

  33. Paradigm shift: from steel to silicon. Past: a lot of steel to focus radiation on a single electronic receiverFuture: many digital receivers and massive data processing synthesize virtual telescope in software Westerbork Radio Observatory LOFAR Hi-Band Antenna (110-240 MHz)

  34. ARTICLE 22 (ITU Radio Regulations) Space services Section V – Radio astronomy in the shielded zone of the Moon 22.22 § 8 1) In the shielded zone of the Moon31 emissions causing harmful inter­ference to radio astronomy observations32 and to other users of passive services shall be prohibited in the entire frequency spectrum except in the following bands: 22.23 a) the frequency bands allocated to the space research service using active sensors; 22.24 b) 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. 22.25 2) In frequency bands in which emissions are not prohibited by Nos. 22.22 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. 22.22.1 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 100 000 km from the centre of the Earth. 3222.22.2 The level of harmful interference is determined by agreement between the administrations concerned, with the guidance of the relevant ITU-R Recommendations. 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. Good “news” …The Moon is radio protected!

  35. Lunar LOFAR:Distributed array of radio sensors • Start with N=100 antennas • Collecting area: • Aeff=N2/8(3 MHz; ~100 m)Aeff~ 0.125 km2(17 football fields or ~400 m dish) • First prototype phase: • Antennas, power, computers, communication, dispatcher • Weight ~1000 kg (payload) • Needs only one Ariane V launch • Separation D = 1 km → 1000 km • Resolution (/D): ~1.6° (D=1 km, 10 MHz) ~6’’ (D=1000 km, 10 MHz) ~ 1’ (D=1000 km, 1 MHz ) • Remote antennas are added later

  36. Ionosphere Opacity: np ~ 1 to 10MHz Phase errors • TIDs – ‘fuzz-out’ sources • ‘Isoplanatic patch’ = few deg = few km • Phase variation proportional to wavelength^2

  37. Global reionization signature in low frequency HI spectra (Gnedin & Shaver 2003) fast 21cm ‘deviations’ at 1e-4 wrt foreground double Spectral index deviations of 0.001

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