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Cosmic reionization and the history of the neutral intergalactic medium LANL

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

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Cosmic reionization and the history of the neutral intergalactic medium LANL

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  1. 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…

  2. Ionized Neutral Reionized

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

  4. Hubble Space Telescope Realm of the Galaxies

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

  6. Reionization: the movie Gnedin 03 8Mpc comoving

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

  8. Gunn-Peterson Effect Fan et al 2006

  9. Gunn-Peterson limits to f(HI) GP = 2.6e4 f(HI) (1+z)^3/2 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

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

  11. 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 TT TE EE Page + 06; Spergel 06

  12. Constraint II: CMB large scale polarization -- Thomson scattering during reionization TT • 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 TE EE Page + 06; Spergel 06

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

  14. Pushing into reionization: QSO 1148+52 at z=6.4 • Highest redshift quasar known (tuniv = 0.87Gyr) • Lbol = 1e14 Lo • Black hole: ~3 x 109 Mo (Willot etal.) • Gunn Peterson trough (Fan etal.)

  15. 1148+52 z=6.42: Gas detection 46.6149 GHz CO 3-2 Off channels Rms=60uJy VLA IRAM • M(H2) ~ 2e10 Mo • zhost = 6.419 +/- 0.001 (note: zly = 6.37 +/- 0.04) VLA

  16. Constrain III: Cosmic Stromgren Sphere • Accurate zhost from CO: z=6.419+/0.001 • 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)

  17. Loeb & Rybicki 2000

  18. 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 2005 P(>xHI) 90% probability x(HI) > curve =tqso/4e7 yrs

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

  20. 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

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

  22. Studying the pristine neutral IGM using redshifted HI 21cm observations (100 – 200 MHz) 1e13 Mo • Large scale structure • cosmic density,  • neutral fraction, f(HI) • Temp: TK, TCMB, Tspin 1e9 Mo

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

  24. Signal I: Global (‘all sky’) reionization signature in low frequency HI spectra Gnedin & Shaver 03 140MHz IGM heating: Tspin= TK > TCMB Ly coupling: Tspin=TK < TCMB Signal ~ 20mK < 1e-4 sky

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

  26. Signal II: HI 21cm Tomography of IGM Zaldarriaga + 2003 z=12 9 7.6 • TB(2’) = 10’s mK • SKA rms(100hr) = 4mK • LOFAR rms (1000hr) = 80mK

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

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

  29. Signal IV: Cosmic web before reionization: HI 21Forest 19mJy z=12 z=8 130MHz 159MHz • Perhaps easiest to detect (use long baselines) • Requires radio sources: expect 0.05 to 0.5 deg^-2 at z> 6 with S151 > 6 mJy? • radio G-P (=1%) • 21 Forest (10%) • mini-halos (10%) • primordial disks (100%)

  30. GMRT 230 MHz – HI 21cm abs toward highest z (~5.2) radio AGN 0924-220 z=5.2 S230MHz = 0.5 Jy GMRT at 230 MHz = z21cm RFI = 20 kiloJy ! 1” 8GHz Van Breugel et al. CO Klamer + M(H2) ~ 3e10 Mo

  31. GMRT 230 MHz – HI 21cm abs toward highest z radio AGN (z~5.2) 232MHz 30mJy 229Mhz0.5 Jy rms(40km/s) = 3mJy rms(20km/s) = 5 mJy N(HI) ~ 2e20TS cm^-2 ?

  32. Signal V: Cosmic Stromgren spheres around z > 6 QSOs • 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 5Mpc 0.5 mJy Wyithe et al. 2006

  33. Signal VI: pre-reionization HI signal, eg. Baryon Oscillations Very low frequency (<75MHz)= Long Wavelength Array • Very difficult to detect • Signal: 10 arcmin, 10mk => S30MHz = 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

  34. Challenge I: Low frequency foreground – hot, confused sky Eberg 408 MHz Image (Haslam + 1982) • 90% = Galactic foreground. • Coldest regions: T ~ 100 (/200 MHz)^-2.6 K • 10% = Egal. radio sources = 1 source/deg^2 with S140 > 1 Jy

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

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

  37. Ionospheric phase errors: The Movie Solution: Wide field ‘rubber screen’ phase self-calibration = ‘peeling’ 15’ Virgo A VLA 74 MHz Lane + 02

  38. Challenge III: Interference 100 MHz z=13 200 MHz z=6 • Solutions -- RFI Mitigation (Ellingson06) • Digital filtering: multi-bit sampling for high dynamic range (>50dB) • Beam nulling/Real-time ‘reference beam’ • LOCATION!

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

  40. 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

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

  42. RFI mitigation: location, location location… 100 people km^-2 1 km^-2 0.01 km^-2 (Briggs 2005)

  43. Challenge IV: Extreme computing LOFAR: IBM Blue Gene/L “Stella” (Falcke) • 0.5 Tbit/s input data rate • 30 Tflop • ~ 12000 PCs • Occupying 6 m2 • 150 KW power consumption Dutch minister of science Blue Gene ~1.7% slower than #1 in Europe (Barcelona) …

  44. Focus: Reionization (power spec,CSS,abs)

  45. 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’ 100MHz 200MHz

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

  47. Destination: Moon! • No interference • No ionosphere (?) • Easy to deploy and maintain (high tolerance electroncs + no moving parts) 10MHz RAE2 1973

  48. 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

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

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