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“First Light” From New Probes of the Dark Ages and Reionization

Judd D. Bowman (Caltech) Hubble Fellows Symposium 2008. “First Light” From New Probes of the Dark Ages and Reionization. Redshifted 21 cm mean brightness temperature. Furlanetto 2006. Redshifted 21 cm anisotropies. 50 mK. 0 . z = 8, x i = 0.3 Data provided by

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“First Light” From New Probes of the Dark Ages and Reionization

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  1. Judd D. Bowman (Caltech) Hubble Fellows Symposium 2008 “First Light” From New Probes of the Dark Ages and Reionization

  2. Redshifted 21 cm mean brightness temperature Furlanetto 2006

  3. Redshifted 21 cm anisotropies 50 mK 0 z = 8, xi = 0.3 Data provided by A. Mesinger & S. Furlanetto

  4. CMB analogy WMAP (Elaborate on standard paradigm) COBE CMB Blackbody (Fundamental paradigm)

  5. Complications • Terrestrial radio frequency interference (RFI) from TV, FM, and other transmitters • Ionospheric distortions of sky positions • Astrophysical foregrounds (dominated by Galactic synchrotron emission and extragalactic continuum sources)

  6. Astrophysical Foregrounds • Sun • Galactic emission: 200 to 10,000 K (~70%) • Extragalactic point sources: 30 to 70 K (~25%) • Galactic radio recombination lines: < 1 K • Free-free in IGM: minimal • (21 cm: < 35 mK) All continuum foregrounds have spectrally smooth power-law profiles

  7. Intensity [K] Spectral index T   Running of spectral index de Oliveira-Costa et al. 2008

  8. Foreground Strategy Wang et al. 2006

  9. 1.4 GHz polarized intensity • 100 times more intense at 150 MHz • Faraday rotation adds significant spectral structure • Enters intensity measurement through mis-calibration Wolleben et al. 2006

  10. Pathfinder experiments under construction: GlobalAnisotropy EDGES MWA (W. Australia) CoRE (Ron Ekers) LOFAR (Neatherlands) GMRT (India) PAPER (W. Australia) Approach: Start from scratch with new instruments that exploit modern digital signal processing technology to address these challenges

  11. Experiment to Detect the Global EOR Signature with Alan E. E. Rogers (MIT/Haystack Observatory) EDGES

  12. Mean (Global) Brightness Temperature Mean brightness temperature Frequency derivative Furlanetto 2006

  13. Instrumental requirements: Do not introduce non-smooth features into the measured the spectrum Simplifications: Ionospheric distortions and polarized foreground greatly reduced for all-sky measurements

  14. Tant Frequency

  15. Reflections: multi-path Tant Frequency

  16. Reflections: impedance mismatch Tant Frequency ADC LNA

  17. Sampling artifacts Tant Frequency ADC Comparison source LNA

  18. EDGES balun ADC “Four-point” antenna Amplifiers and switch Ground screen

  19. EDGES “First Light” First measured spectrum partially calibrated, western Australia 1.5 sky hours Bowman et al. 2008

  20. EDGES: Smoothness Residuals after 7th order polynomial fit to spectrum rms vs. integration time Measuredrms = 75 mK (Instrumentally limited) Black line: smoothed to 2.5 MHz Bowman et al. 2008

  21. EDGES: Upper Limit Upper limit: T21 < 450 mK for instantaneous reionization at z = 8 z T21 Expected 21 cm rms 7.5 mK zr = 8 Bowman et al. 2008

  22. Implications and Future Work • Preliminary constraint: T21 < 450 mK (if reionization occurred abruptly at z  8) • Demonstrated viable approach First run within order of magnitude (75 mK [rms] compared to  7.5 mK) • Clear path to improve performance Analog to digital converter identified as limiting component Increase bandwidth of antenna impedance match • Should determine duration of reionization or constrain to: z  2 or better • May be able to detect heating transition of IGM and/or exotic PBHs

  23. Murchison Widefield Array MIT, Harvard/CfA, Australian Consortium, WA government, RRI (India) MWA

  24. MWA The VLA in a new way… • Collecting area: 8000 m2 • Spectral coverage: 80 to 300 MHz • Instantaneous bandwidth: 32 MHz (z = 2) • Spectral resolution: 10 kHz (40 kHz) • 512 antenna “tiles” within 1.5 km diameter • Field of view: 100 to 1000 deg2 • Angular resolution: 3 to 10 arcmin • Sky noise dominated

  25. MWA: Antenna Tile 1 2 3

  26. The Catalog of MWA Antennae + 480 more by early 2009

  27. MWA: EOR Observing Plan Primary field: RA 60.00, Dec -30.00 1250 hours available Divided between 2 bands 6 < z < 9 Secondary field: RA 155.00, Dec -10.00, 450 hours available 6 < z < 7 K

  28. 1 Gpc [6<z<9] (6000 channels) MWA:Data Cube 8 Gpc (1000 pixels) z = 7.68 xi=0.33 z = 8.16 xi=0.11 z = 6.89 xi=0.52 Zahn et al. 2007

  29. MWA: Thermal Uncertainty xi <0.1 z = 6 z = 8 z = 10 z = 12 Lidz et al. 2008 Bowman et al. 2006

  30. MWA: Antenna Distribution Antenna layout Baseline distribution Rotation synthesis • 125000 baselines • 10% in tightly packed core • Completely sample uv-plane within 500 wavelengths • Short baselines probe both large and small spatial scales

  31. MWA Schedule • 1/16th collecting area installed, digital systems coming next month • First engineering run: August 2008 • 100 hours on primary field w/ 32 tiles, 32 MHz • Test calibration, all-sky map, polarized sources, RRLs • Complete array in early 2009 • Science observing mid-2009 through 2010

  32. Summary • Pathfinder experiments for both global and anisotropy signals are in progress to demonstrate foreground mitigation and detect signal at z > 6 • Feasible and compelling near-term science goals to determine redshift (xi <0.1 @ z8) and duration of reionization (z> 2 @ z<13)

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