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Judd D. Bowman Arizona State University Alan Rogers MIT/Haystack Observatory May 26, 2011 Experiment to Detect the Global EoR Signature (EDGES)
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Outline 1.Brief motivation 2.Instrument Overview 3.Results a.Reionization b.Galactic synchrotron spectral index c.Radio Frequency Interference 4.Looking ahead
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The global 21 cm signal Pritchard & Loeb (2011)
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EDGES
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EDGES – Experiment to Detect the Global EoR Signature CSIRO support trailer Antenna Murchison Radio-astronomy Observatory (MRO), Western Australia
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in from antenna to 2 nd stage calibration source 2 nd stage amp dithering noise source to digitizer LNA switch
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Technical challenges Cannot (easily) create external calibrator, difficult matching sky temperature across band Cannot fully characterize antenna in lab – Beam pattern changes with frequency – Antenna and LNA impedance change with frequency, in general poor match – Receiver noise reflections Multi-path reflections Non-linear effects prevent ideal comparison- switch calibration
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EDGES measured spectrum Murchison Radio-astronomy Observatory (MRO) Aug 20 – Oct 20, 2009 1440 wall-clock hours on sky 500 hours after RFI cuts 50 hours eff. integration +15 dB Bowman & Rogers (Nature, 2010)
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EDGES parameter estimation #1: 21 cm reionization model #2: Foreground model Pritchard & Loeb (2010, submitted) 2 science parameters: z and z r 4-19 nuisance parameters: a n (ACKK!!)
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EDGES lower limit on duration Bowman & Rogers (Nature, 2010) z r > 0.06 for 6 < z r < 13 (95% confidence)
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EDGES absolute calibration T gal = 237 10 K (3 sigma) @ 150 MHz 100-200 MHz: = 2.5 0.1 (3 sigma) 150-408 MHz: = 2.52 0.04 (3 sigma) Rogers & Bowman 2008
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Integrated RFI (time excision only – by broadband power level in FM, Orbcomm, DTV bands: 30% removal) Note: shows every channel that ever had RFI over 3 months
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Orbcomm LEO satellite constellation
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Outline 1.Brief motivation 2.Instrument Overview 3.Results a.Galactic synchrotron spectral index b.Reionization c.Radio Frequency Interference 4.Looking ahead
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EDGES reionization forecast Pritchard & Loeb (2010)
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EDGES reionization forecast Morandi & Barkana (2011)
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Physical model templates EOR absorption x 10 4 Data deviates from power law primarily due to the antenna mismatch factor 1 - |G| 2 AEER
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Summary Identified key technical challenges and viable approaches – See AEER talk tomorrow morning – CoRE (RRI), Bighorns (Curtin University), DARE (U. Colorado), LWA cosmic dawn, Peterson Beginning to rule out rapid reionization histories – z>0.06 between 6<z<13 – First reionization science from any redshifted 21 cm experiment Ancillary science and supporting measurements – Galactic synchrotron spectral index – Deepest broadband spectrum ever acquired at 5 mK rms – RFI properties of remote sites in US and Australia (more to come) More compelling 21 cm science in the near future – Constrain derivative of neutral fraction for generic reionization histories – Attempt first detection of z=15-25 absorption feature to probe UV emission from first stars and early IGM heating
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