anadian ydrogen ntensity apping xperiment chimechime chimechime wigglez dark ages stars 13.7gy cmb...
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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
Outline
• Cosmo Context• HI Mapping of BAO• FFT Telescopes• CHIME
anadian
ydrogen
ntensity
apping
xperiment
Keith VanderlindeCIfAR C&G 2012 AGM
CHIME
CHIME
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!
The Primordial Plasma
• Photons• Neutrinos• Dark Matter• Electrons + Baryons
Hu
& W
hite
, Sci
entif
ic A
mer
ican
, 200
4
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
Post-Decoupling Radial Profile
BAO are “frozen in,” ~150 co-moving Mpc.
BAO peak
Eisenstein
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
BAO as a standard ruler
1100
WMAP
. . .
. . .
BA
O “
Siz
e” a
t z
How do we fill this in?
Anderson et al. 2012
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
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!)
FFT TelescopeHaslam et al. 1982
+ + + + + + ++ + + + + + ++ + + + + + ++ + + + + + ++ + + + + + +
+ + + + + + ++ + + + + + +
Sky
Gro
und
E
Sam
pled
G
roun
dM
easu
red
Sky
Normal Telescope
x
Use a mirror (or lens) to focus light onto a detector.
noise ~ Tsky + Tamp
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)
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)
“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)
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! --
Cylinder TelescopesHybrid: 1D Dish + 1D FFT
Single Antenna
Long Narrow Beam
Cylinder TelescopesHybrid: 1D Dish + 1D FFT
N antennas
N “Formed Beams”
FFT
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
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
CHIME Sensitivity to BAO
spectrum w/ BAOspectrum w/o BAO
CHIME Cosmology Forecast
(1+z)3
^
(Preliminary!)
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.
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
CHIME Survey Volume
For cosmic variance limited survey, sensitivity ~ volume.CHIME’s sensitivity to D.E. within ~2x of c.v. limited.
The End