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