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anadian
ydrogen
ntensity
apping
xperiment
CHIME
CHIME
WiggleZ
Dark
Ages
Stars
13.7Gy
CMB Big Bang
Reionization
110
0
z ∞ 50 9 5 3 2 1
SDSS
7GyCHIME
300ky
0
500My
Age of Universe
Keith VanderlindeCIfAR C&G 2012 AGM
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Outline
• Cosmo Context• HI Mapping of BAO• FFT Telescopes• CHIME
anadian
ydrogen
ntensity
apping
xperiment
Keith VanderlindeCIfAR C&G 2012 AGM
CHIME
CHIME
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Composition of the Universe
Composition Images fromNASA / WMAP Science Team
w = -1 ± 0.2
Frieman et al. 2008
-4 -3 -2 -1 0 1Log (a)
?
• Can study via growth of space.• Need standard ruler over wide z range!
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The Primordial Plasma
• Photons• Neutrinos• Dark Matter• Electrons + Baryons
Hu
& W
hite
, Sci
entif
ic A
mer
ican
, 200
4
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Baryon Acoustic Oscillations• random background of primordial fluctuations
• each fluctuation emits a pressure wave
• at decoupling, the size of this wave is frozen
(Eisenstein) Komatsu et al. 2010
Cold Stack Hot Stack
Measured in the CMB
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Post-Decoupling Radial Profile
BAO are “frozen in,” ~150 co-moving Mpc.
BAO peak
Eisenstein
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Buetler et al, 2011
6dFGS
BAO Observations
Blake et al, 2011
WiggleZ
Detected in galaxy correlations!
SDSS
Eisenstein et al, 2005
mh2 = 0.12, mh2 = 0.024mh2 = 0.13, mh2 = 0.024mh2 = 0.14, mh2 = 0.024mh2 = 0.105, mh2 = 0.0
Sanchez et al, 2012
BOSS-CMASS
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BAO as a standard ruler
1100
WMAP
. . .
. . .
BA
O “
Siz
e” a
t z
How do we fill this in?
Anderson et al. 2012
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Optical Maps of Structure
Sloan DigitalSky Survey (SDSS)
Blanton et al. (2003)
Get spectroscopic redshifts on lots of galaxies.
Works!
But:• expensive• hard at z>1
BAOScaleBAOScale
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Hydrogen Intensity Mapping
For BAO, no need to resolve galaxies individually. Use 21cm HI line.
For 15 co-moving Mpc resolution at z~1-2 (~20’), need:
Unresolved galaxies,
resolved BAO.
BAOScaleBAOScale
a) 100m telescope + decades of survey
b) Interferometer + HUGE correlator
c) FFT telescope
(See Ue-Li’s talk!)
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FFT TelescopeHaslam et al. 1982
+ + + + + + ++ + + + + + ++ + + + + + ++ + + + + + ++ + + + + + +
+ + + + + + ++ + + + + + +
Sky
Gro
und
E
Sam
pled
G
roun
dM
easu
red
Sky
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Normal Telescope
x
Use a mirror (or lens) to focus light onto a detector.
noise ~ Tsky + Tamp
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x
x
x
x
x
x
xxx
Phased Array Interferometer
Record signals at the dish,add delay to mimic reflection,
sum recorded signals.
noise ~ Tsky + Tamp sqrt(Namp)
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Phased Array Interferometer
x
x
x
x
x
x
xx
x
Throw away the dish.Save a big pile of money.
noise ~ Tsky + Tamp sqrt(Namp)
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“Pointing” a Phased Array
x
x
x
x
x
x
xx
x
Add delays with cabling to mimic pointing.Spend your pile of money on a computer, do this digitally.
noise ~ Tsky + Tamp sqrt(Namp)
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Beam-forming Telescopes
xxxxxx
xx
x
Record signals on the ground, digitally delay and add.
N beams, without aliasing, for spacing < /2.Mapping speed ~ Nant x single-dish. (N2 for Tsky >> Tamp)
noise ~ Tsky + Tamp sqrt(Nant)
-- per beam! --
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Cylinder TelescopesHybrid: 1D Dish + 1D FFT
Single Antenna
Long Narrow Beam
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Cylinder TelescopesHybrid: 1D Dish + 1D FFT
N antennas
N “Formed Beams”
FFT
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100m
100m
• 400-800MHz band21cm from z ~ 0.8 - 2.5
• Resolution: 1MHz, 13-26’ <10% BAO scale
•Drift scan, no moving parts20,000 deg2 coverage
Canadian Hydrogen Intensity Mapping Experiment
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1
2
Record Data
Readout & Correlator
1) Sample & channelize• 1 ADC per antenna• 8-bit @ 800MSPS
2) Correlate• 1 node per freq band• N2 is tricky: Pflops of processing, Exabytes of storage (!!)• Do FFT beamforming, plus partial N2 to calibrate
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CHIME Sensitivity to BAO
spectrum w/ BAOspectrum w/o BAO
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CHIME Cosmology Forecast
(1+z)3
^
(Preliminary!)
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Pulsars & Radio TransientsEvery day, CHIME observes:• every point in the northern celestial hemisphere• across an octave in frequency (400-800MHz)• for between 5 minutes and hours (depending on Decl.)• with s timing resolution & accuracy
Can’t actually process every point at that rate.
Tee data off to monitor known locations,systematically search for new sources.
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Mapping the Observable
Universe
Dark
AgesWiggleZ
Stars
13.7Gy
CMB Big Bang
Reionization
SDSS
110
0
z ∞ 50 9 5 3 2 1
7GyCHIME
(400 co-moving Gpc3)
300ky
0
500My
Age of Universe
CHIME will:• survey BAO• measure thegrowth of space• from 0.8<z<2.5• over a volume of ~400 co-moving Gpc3
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CHIME Survey Volume
For cosmic variance limited survey, sensitivity ~ volume.CHIME’s sensitivity to D.E. within ~2x of c.v. limited.
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The End