Judd D. BowmanArizona State University

Alan RogersMIT/Haystack Observatory

May 26, 2011

Experiment to Detect the Experiment to Detect the Global EoR Signature (EDGES)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

CSIROsupport trailerAntenna

Murchison Radio-astronomy Observatory (MRO), Western Australia

in from antenna

to 2nd stage

calibration source

2nd 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, 2009

1440 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

m

n

nnF zaT

0

)1(

Pritchard & Loeb (2010, submitted)

2 science parameters: z and zr 4-19 nuisance parameters: an (ACKK!!)

EDGES lower limit on duration

Bowman & Rogers (Nature, 2010)

zr > 0.06 for 6 < zr < 13 (95% confidence)

EDGES absolute calibration

Tgal = 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

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 104

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