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C anadian
H ydrogen
I ntensity
M apping
E xperiment
z
0
Age of
Universe
Big Bang
CMB
CHIME
∞
9
5
3
2
1
13.7Gy
SDSS
WiggleZ
Reionization
Keith Vanderlinde
CIfAR C&G 2012 AGM
C anadian
H ydrogen
I ntensity
M apping
E xperiment
Outline
• Cosmo Context
• HI Mapping of BAO
• FFT Telescopes
• CHIME
Keith Vanderlinde
CIfAR C&G 2012 AGM
Composition of the Universe
-4
-3
Log (a)
-2
-1
1
0
Frieman et
al. 2008
?
w = -1 ± 0.2
• Can study via growth of space.
• Need standard ruler over wide z range!
Composition Images from
NASA / WMAP Science Team
• Photons
• Neutrinos
• Dark Matter
• Electrons + Baryons
Hu & White, Scientific American, 2004
The
Primordial
Plasma
Baryon Acoustic Oscillations
• random background of primordial fluctuations
• each fluctuation emits a pressure wave
• at decoupling, the size of this wave is frozen
Measured in the CMB
Cold Stack
(Eisenstein)
Hot Stack
Komatsu et al. 2010
Post-Decoupling Radial Profile
Eisenstein
BAO peak
BAO are “frozen in,” ~150 co-moving Mpc.
BAO Observations
Detected in galaxy correlations!
Buetler et al, 2011
Eisenstein et al, 2005
SDSS
6dFGS
Blake et al, 2011
WiggleZ
mh2 = 0.12, mh2 = 0.024
mh2 = 0.13, mh2 = 0.024
mh2 = 0.14, mh2 = 0.024
mh2 = 0.105, mh2 = 0.0
Sanchez et al, 2012
BOSS-CMASS
BAO as a standard ruler
Anderson et al. 2012
BAO “Size” at z
WMAP
...
...
1100
How do we fill this in?
Optical Maps
of Structure
Get spectroscopic
redshifts on lots
of galaxies.
Works!
BAO
Scale
But:
• expensive
• hard at z>1
Blanton et al. (2003)
Sloan Digital
Sky Survey (SDSS)
Hydrogen Intensity
Mapping
(See Ue-Li’s talk!)
For BAO, no need
to resolve galaxies
individually. Use
21cm HI line.
For 15 co-moving
Mpc resolution at
z~1-2 (~20’), need:
a) 100m telescope +
decades of survey
b) Interferometer +
HUGE correlator
c) FFT telescope
BAO
Scale
Unresolved
galaxies,
resolved BAO.
FFT Telescope
+++++++
+++++++
+++++++
+++++++
+++++++
+++++++
+++++++
Sampled
Ground
Ground E
Sky
Measured
Sky
Haslam et al. 1982
Normal Telescope
noise ~ Tsky + Tamp
x
Use a mirror (or lens) to focus
light onto a detector.
Phased Array Interferometer
noise ~ Tsky + Tamp sqrt(Namp)
x
x
x
x
x
x
x
x
x
Record signals at the dish,
add delay to mimic reflection,
sum recorded signals.
Phased Array Interferometer
noise ~ Tsky + Tamp sqrt(Namp)
x
x
x
x
x
x
x
x
x
Throw away the dish.
Save a big pile of money.
“Pointing” a Phased Array
noise ~ Tsky + Tamp sqrt(Namp)
x
x
x
x
x
x
x
x
x
Add delays with cabling to mimic pointing.
Spend your pile of money on a computer, do this digitally.
Beam-forming Telescopes
Record signals on the ground, digitally delay and add.
noise ~ Tsky + Tamp sqrt(Nant)
-- per beam! --
x
x
x
x
x
x
x
x
x
N beams, without aliasing, for spacing < /2.
Mapping speed ~ Nant x single-dish. (N2 for Tsky >> Tamp)
Cylinder Telescopes
Hybrid: 1D Dish + 1D FFT
Single
Antenna
Long
Narrow
Beam
Cylinder Telescopes
Hybrid: 1D Dish + 1D FFT
N
“Formed
Beams”
N antennas
Canadian Hydrogen Intensity Mapping Experiment
100m
100m
• 400-800MHz band
21cm from z ~ 0.8 - 2.5
• Resolution: 1MHz, 13-26’
<10% BAO scale
•Drift scan, no moving parts
20,000 deg2 coverage
Readout & Correlator
1
1) Sample & channelize
• 1 ADC per antenna
• 8-bit @ 800MSPS
2
2) Correlate
Record Data
• 1 node per freq band
• N2 is tricky: Pflops of processing, Exabytes of storage (!!)
• Do FFT beamforming, plus partial N2 to calibrate
CHIME Sensitivity to BAO
spectrum w/ BAO
spectrum w/o BAO
CHIME Cosmology Forecast
(1+z)3
^
(Preliminary!)
Pulsars & Radio Transients
Every 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.
0
Mapping the
Observable
Universe
Age of
Universe
Big Bang
CMB
CHIME
(400 co-moving Gpc3)
z
∞
CHIME will:
• survey BAO
• measure the
growth of space
• from 0.8<z<2.5
• over a volume of
~400 co-moving Gpc3
9
5
Reionization
3
2
1
13.7Gy
SDSS
WiggleZ
CHIME Survey Volume
For cosmic variance limited survey, sensitivity ~ volume.
CHIME’s sensitivity to D.E. within ~2x of c.v. limited.
The End