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

2. Redshifted 21 cm mean brightness temperature Furlanetto 2006

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

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

5. Complications 1.Terrestrial radio frequency interference (RFI) from TV, FM, and other transmitters 2.Ionospheric distortions of sky positions 3.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. de Oliveira-Costa et al. 2008 Intensity [K] Spectral index T    Running of spectral index

8. Foreground Strategy Wang et al. 2006

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

10. Pathfinder experiments under construction: GlobalAnisotropy EDGESMWA (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. EDGES Experiment to Detect the Global EOR Signature with Alan E. E. Rogers (MIT/Haystack Observatory)

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

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. Frequency T ant

15. Reflections: multi-path Frequency T ant

16. Reflections: impedance mismatch Frequency T ant ADC LNA

17. Sampling artifacts Frequency T ant ADC LNA Comparison source

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

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

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

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

22. Implications and Future Work Preliminary constraint: T 21 < 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. MWA Murchison Widefield Array MIT, Harvard/CfA, Australian Consortium, WA government, RRI (India)

24. MWA The VLA in a new way… Collecting area: 8000 m 2 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 deg 2 Angular resolution: 3 to 10 arcmin Sky noise dominated

25. MWA: Antenna Tile 25 1 2 3

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

27. MWA: EOR Observing Plan K 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

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

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

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

31. MWA Schedule 1/16 th 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. 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 (x i 2 @ z<13) Summary