judd d. bowman arizona state university alan rogers mit/haystack observatory may 26, 2011
DESCRIPTION
Experiment to Detect the Global EoR Signature (EDGES). Judd D. Bowman Arizona State University Alan Rogers MIT/Haystack Observatory May 26, 2011. Outline. Brief motivation Instrument Overview Results Reionization Galactic synchrotron spectral index Radio Frequency Interference - PowerPoint PPT PresentationTRANSCRIPT
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