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Radio astronomy: Probing the Cosmic Reionization Manchester, Oct 2007 Chris Carilli (NRAO)

Radio astronomy: Probing the Cosmic Reionization Manchester, Oct 2007 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.

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Radio astronomy: Probing the Cosmic Reionization Manchester, Oct 2007 Chris Carilli (NRAO)

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  1. Radio astronomy: Probing the Cosmic Reionization Manchester, Oct 2007 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. Last phase of cosmic evolution to be explored • Benchmark in cosmic structure formation indicating the formation of the first luminous objects. • HI 21cm line is most direct, incisive probe of structure formation during, and process of, reionization. • Radio(cm/mm) observations reveal the gas, dust, star formation, and AGN in the earliest galaxies Dark Ages Cosmic reionization

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

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

  7. OI • Not ‘event’ but complex process, large variance: zreion ~ 14 to 6 • Good evidence for qualitative change in nature of IGM at z~6 ESO

  8. 3, integral measure? Geometry, pre-reionization? Local ionization? OI Abundance? Saturates, HI distribution function, pre-ionization? Local ioniz.? • Current probes are all fundamentally limited in diagnostic power • Need more direct probe of process of reionization = HI 21cm line ESO

  9. 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: TK, TCMB, Tspin • Heating: Ly, Xrays, shocks

  10. Signal I: Global (‘all sky’) reionization signature in low frequency HI spectra IGM heating: T_spin=T_K > T_CMB Lya coupling: T_spin=T_K < T_CMB Gnedin & Shaver 03 21cm ‘deviations’ < 1e-4 wrt foreground

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

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

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

  14. Signal IV: Cosmic web before reionization: HI 21Forest 19mJy z=12 z=8 130MHz • radio G-P (=1%) • 21 Forest (10%) • mini-halos (10%) • primordial disks (100%) • expect 0.05 to 0.5 deg^-2 at z> 6 with S_151 > 6 mJy

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

  16. Challenge I: Low frequency foreground – hot, confused sky Eberg 408 MHz Image (Haslam + 1982) Coldest regions: T = 100 (n/200 MHz)^-2.6 K Highly ‘confused’: 1 source/deg^2 with S_0.14 > 1 Jy

  17. Solution: spectral decomposition (eg. Morales, Gnedin…) • Foreground = non-thermal = featureless over ~ 100’s MHz • Signal = fine scale structure on scales ~ few MHz Signal/Sky ~ 2e-5 10’ FoV; SKA 1000hrs Cygnus A 500MHz 5000MHz Simply remove low order polynomial or other smooth function?

  18. Challenge II: Ionospheric phase errors: varying e- content TID 100” -100” 74MHz Lane 03 • ‘Isoplanatic patch’ = few deg = few km • Phase variation proportional to wavelength^2 • Solution: Wide field ‘rubber screen’ phase self-calibration

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

  20. First galaxies: ALMA/EVLA CO redshift coverage Epoch of Reionization: First galaxies: standard molecular transitions redshift to cm regime • Total gas mass • Gas dynamics • Gas excitation • High density gas tracers

  21. First galaxies -- Radio astronomy into cosmic reionization z ~ 6 QSO host galaxies: molecular gas and dust VLA z=6.42 50K PdBI FWHM=350 km/s Radio-FIR correlation • Mdust ~ 1e8 Mo • Dust heating: star formation or AGN? • Follows Radio-FIR correlation: SFR ~ 3000 Mo/yr • Giant reservoirs of molecular gas ~2e10 Mo = fuel for star formation. • Currently: 2 solid detections, 2 likely at z~6

  22. J1148+52: VLA imaging of CO3-2 VLA imaging of gas at subkpc resolution 0.4”res rms=50uJy at 47GHz 1” 5.5kpc 0.15” res • Not just circumnuclear disk. • Mdyn~ 4e10Mo ~ Mgas>> Mbulge ~1e12 Mo predicted by M- • Separation = 0.3” = 1.7 kpc • TB = 20K => Typical of starburst nuclei

  23. [CII] 158um ISM gas cooling line at z=6.4 30m 256GHz Maiolino etal • C+ = workhorse line for z>6 galaxies with ALMA • Structure identical to CO 3-2” (~ 5 kpc) => distributed gas heating = star formation? • SFR ~ 6.5e-6 L[CII] ~ 3000 Mo/yr CII PdBI Walter et al. CII + CO 3-2 1”

  24. Higher Density (>1e4 cm^-3) Tracers: HCN, CN, & HCO+, HCN 1-0 HCO+ 1-0 Riechers • Linearly correlated with FIR => dense gas directly associated with star forming clouds • Lines 5-10x fainter than CO • ncr > 1e7cm^-3 for higher orders => higher order not (generally) excited? • Dense gas tracers best studied with cm telescopes 200uJy

  25. The need for collecting area: pushing to normal galaxies at high redshift -- spectral lines cm telescopes: low order molecular transitions (sub)mm: high order molecular lines + fine structure lines

  26. The need for collecting area: continuum A Panchromatic view of galaxy formation Arp 220 vs z cm: Star formation, AGN (sub)mm Dust, molecular gas Near-IR: Stars, ionized gas, AGN

  27. Radio astronomy – Reionization and 1st galaxies • ‘Twilight zone’: study of first light limited to near-IR to radio wavelengths • First constraints: GP, CMBpol => reionization is complex and extended: z_reion = 6 to 14 • HI 21cm: most direct probe of reionization • Low freq pathfinders: All-sky, PS, CSS, Abs • SKA: imaging of IGM • First galaxies: cm/mm -- gas, dust, star formation, AGN

  28. Signal VI: pre-reionization HI signal: ‘richest of all cosmological data sets’ eg. Baryon Oscillations (Barkana & Loeb) • Very difficult to detect ! • z=50 => n = 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

  29. Destination: Moon! • No interference (ITU protected zone) • No ionosphere (?) • Easy to deploy and maintain (high tolerance electronics + no moving parts) 10MHz Needed for probing ‘Dark ages’: z>30 => freq < 50 MHz RAE2 1973

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