Judd D. Bowman Arizona State University Alan Rogers MIT/Haystack Observatory May 26, 2011 Experiment to Detect the Global EoR Signature (EDGES)

Outline 1.Brief motivation 2.Instrument Overview 3.Results a.Reionization b.Galactic synchrotron spectral index c.Radio Frequency Interference 4.Looking ahead

The global 21 cm signal Pritchard & Loeb (2011)

EDGES

EDGES – Experiment to Detect the Global EoR Signature CSIRO support trailer Antenna Murchison Radio-astronomy Observatory (MRO), Western Australia

in from antenna to 2 nd stage calibration source 2 nd stage amp dithering noise source to digitizer LNA switch

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

EDGES measured spectrum Murchison Radio-astronomy Observatory (MRO) Aug 20 – Oct 20, wall-clock hours on sky 500 hours after RFI cuts 50 hours eff. integration +15 dB Bowman & Rogers (Nature, 2010)

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!!)

EDGES lower limit on duration Bowman & Rogers (Nature, 2010)  z r > 0.06 for 6 < z r < 13 (95% confidence)

EDGES absolute calibration T gal = 237  10 K (3 150 MHz MHz:  = 2.5  0.1 (3 sigma) MHz:  = 2.52  0.04 (3 sigma) Rogers & Bowman 2008

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

Orbcomm LEO satellite constellation

Outline 1.Brief motivation 2.Instrument Overview 3.Results a.Galactic synchrotron spectral index b.Reionization c.Radio Frequency Interference 4.Looking ahead

EDGES reionization forecast Pritchard & Loeb (2010)

EDGES reionization forecast Morandi & Barkana (2011)

Physical model templates EOR absorption x 10 4 Data deviates from power law primarily due to the antenna mismatch factor 1 - |G| 2 AEER

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