The Sunyaev-Zel’dovich Effect
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The Sunyaev-Zel’dovich Effect. Jason Glenn APS Historical Perspective Physics of the SZ Effect -------------------------------------------- Previous Observations & Results Bolocam Imminent Experiments Future Work References. Historical Perspective.

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The Sunyaev-Zel’dovich Effect

Jason Glenn

APS

Historical Perspective

Physics of the SZ Effect

--------------------------------------------

Previous Observations & Results

Bolocam

Imminent Experiments

Future Work

References


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Historical Perspective

  • CMB discovered in 1964 by Penzias and Wilson

  • COBE 1989: perfect blackbody to 1/105, primary anisotropies measured

  • However, in 1970 Sunyaev & Zel’dovich predicted the SZ effect: secondary anisotropies in the CMB

TCMB = 2.725 K


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Physics of the SZ Effect

Mechanism & Thermal Effect

CMB photons

T = (1 + z) 2.725K

galaxy cluster

with hot ICM

z ~ 0 - 3

observer

z = 0

scattered

photons

(hotter)

Spectral

shift

Sunyaev & Zeldovich (1970)

last scatteringsurface

z ~ 1100

CMB photons have a ~1% chance of inverse Compton scattering off of the ICM electrons; photon number is conserved


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Physics of the SZ Effect

Functional Form

y parameter

  • Temperature shift proportional to the gas pressure, neTe, & mass dl

  • CMB photon energies boosted by ~kTe/(mec2)

  • kTe ~ 10 keV, Te ~ 108 K  relativistic

  • x = h/(kTe)

  • f(x) is the spectral dependence

  • Notice that the temperature shift is redshift independent  unbiased surveys for clusters


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Physics of the SZ Effect

The Kinetic Effect: a Doppler boost from the peculiar velocity of the cluster

Spectral distortion:

Null in thermal  measure kinetic

Increment

Kinetic effect is small

Decrement


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Physics of the SZ Effect

What the thermal effect looks like

  • Simulations, of course!

  •  = 2 mm

  • “Maps” are 1° on a side

  • SZ effect is an increment at 2 mm


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Physics of the SZ Effect

The Angular Power Spectrum

  • Secondary anisotropies can be measured independent of cluster detection

  • l is the multipole number (as in quantum mechanics); (°) ~ 200°/l

  • Vertical units: T2 – power usually measured as an excess variance above the noise, Cl is per l – there are more independent multipoles at high l

  • Dashed and dotted lines are models

  • The signals are small: ~ 15 mK @ 30 GHz, ~ 5 mK @ 150 GHz

  • Tentative detections so far (more on this Friday)

Green is 30 GHz, or 1 cm

Pink is 150 GHz, or 2 mm


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Physics of the SZ Effect

Cosmological Utility

  • What can be measured when combined with other observations:

  • H0

  • Cluster masses

  • Cluster abundance as a function of redshift

  • , , w

  • Spectral index of initial perturbations (non-Gaussianity)

  • Cluster evolution

  • Next, we’ll discuss SZ observations and some results


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Previous Observations

Images from Interferometers

  • Image from Carlstrom group using OVRO/BIMA interferometer at 30 GHz

  • Spectral measurements a compendium – confirms spectrum through RJ tail

  • To date, only pointed observations toward massive clusters

  • Measurements of the kinetic effect will be very hard, depending on precision of multiband calibration


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Some Questions

  • What are the tradeoffs between 30 GHz (1 cm) and 150/270 GHz (2mm/1mm) observations?


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Some Questions

  • What are the tradeoffs between 30 GHz (1 cm) and 150/270 GHz (2mm/1mm) observations?

    • The amplitude of the SZ thermal effect is larger at 30 GHz


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Some Questions

  • What are the tradeoffs between 30 GHz (1 cm) and 150/270 GHz (2mm/1mm) observations?

    • The amplitude of the SZ thermal effect is larger at 30 GHz

    • Contamination by cluster, foreground, and background radio point sources (quasars) would be a problem at 30 GHz.


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Some Questions

  • What are the tradeoffs between 30 GHz (1 cm) and 150/270 GHz (2mm/1mm) observations?

    • The amplitude of the SZ thermal effect is larger at 30 GHz

    • Contamination by cluster, foreground, and background radio point sources (quasars) would be a problem at 30 GHz.

    • Contamination by dust from background, lensed galaxies is a potential problem at 1 mm.


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Some Questions

  • What are the tradeoffs between 30 GHz (1 cm) and 150/270 GHz (2mm/1mm) observations?

    • The amplitude of the SZ thermal effect is larger at 30 GHz

    • Contamination by cluster, foreground, and background radio point sources (quasars) would be a problem at 30 GHz.

    • Contamination by dust from background, lensed galaxies is a potential problem at 1 mm.

    • In practice, the angular resolution achievable with each is about the same because bolometer arrays are used for short-wavelength observations and interferometers are used for long-wavelength observations.


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Some Questions

  • What are the tradeoffs between 30 GHz (1 cm) and 150/270 GHz (2mm/1mm) observations?

    • The amplitude of the SZ thermal effect is larger at 30 GHz

    • Contamination by cluster, foreground, and background radio point sources (quasars) would be a problem at 30 GHz.

    • Contamination by dust from background, lensed galaxies is a potential problem at 1 mm.

    • In practice, the angular resolution achievable with each is about the same because bolometer arrays are used for short-wavelength observations and interferometers are used for long-wavelength observations.

    • 1 mm and 2 mm observations are necessary to measure the kinetic SZ effect.


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Some Questions

  • What are the tradeoffs between 30 GHz (1 cm) and 150/270 GHz (2mm/1mm) observations?

    • The amplitude of the SZ thermal effect is larger at 30 GHz

    • Contamination by cluster, foreground, and background radio point sources (quasars) would be a problem at 30 GHz.

    • Contamination by dust from background, lensed galaxies is a potential problem at 1 mm.

    • In practice, the angular resolution achievable with each is about the same because bolometer arrays are used for short-wavelength observations and interferometers are used for long-wavelength observations.

    • 1 mm and 2 mm observations are necessary to measure the kinetic SZ effect.

    • Emission/absorption by the atmosphere is not a huge problem at long wavelengths for interferometers because the noise between telescopes is not highly correlated.


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Some Questions

  • What are the tradeoffs between 30 GHz (1 cm) and 150/270 GHz (2mm/1mm) observations?

    • The amplitude of the SZ thermal effect is larger at 30 GHz

    • Contamination by cluster, foreground, and background radio point sources (quasars) would be a problem at 30 GHz.

    • Contamination by dust from background, lensed galaxies is a potential problem at 1 mm.

    • In practice, the angular resolution achievable with each is about the same because bolometer arrays are used for short-wavelength observations and interferometers are used for long-wavelength observations.

    • 1 mm and 2 mm observations are necessary to measure the kinetic SZ effect.

    • Emission/absorption by the atmosphere is not a huge problem at long wavelengths for interferometers because the noise between telescopes is not highly correlated.

    • In contrast, atmospheric noise is much worse at short wavelengths – much worse than anticipated!


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Some Questions

  • What are the tradeoffs between 30 GHz (1 cm) and 150/270 GHz (2mm/1mm) observations?

    • Clearly, we need both.


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Atmospheric Noise

Emission, rather than absorption, is the primary problem: fluctuation in the arrival rate of background photons from water molecules in the sky (and the telescope, the ground, the instrument…)

300 m

cm band

The sky over Mauna Kea

Emission = 1 - Transmission

2 mm

1 mm

Bolocam


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Physics of the SZ Effect

The Angular Power Spectrum

We need more high-l data!

Green is 30 GHz, or 1 cm

Pink is 150 GHz, or 2 mm


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Bolocam

Detectors

Incoming Photons

Absorber

Weak Thermal

Link

Q

Si3N4 micromesh “spider web” bolometer

JPL Micro Devices Lab

Bath

(T ≤ 270 mK)


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Bolocam

Bolometers

In 1878, Samuel Pierpont Langley invented the bolometer.

Oh, Langley devised a bolometer:

It’s really a kind of thermometer

Which measures the heat

From a polar bear’s feet

At a distance of half a kilometer1.

1Anonymous


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Bolocam

Bolometers

In 1878, Samuel Pierpont Langley invented the bolometer.

Oh, Langley devised a bolometer:

It’s really a kind of thermometer

Which measures the heat

From a polar bear’s feet

At a distance of half a kilometer1.

1Anonymous

With Bolocam on the CSO, we can detect a polar bear’s foot with a S/N of one at a distance of 3 km in one second of integration time2.

2(In good weather!)


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Bolocam

Cryostat

Instrument

CSO

5 in.

Focal Plane

Bolometer Array

Collaborators

(Cardiff, Caltech, JPL, & CU)

P.A.R. Ade, J.E. Aguirre, J.J. Bock, S.F. Edgington, A. Goldin, S.R. Golwala, D. Haig, A.E. Lange, G.T. Laurent, P.R. Maloney, P.D. Mauskopf, P. Rossinot, J. Sayers, P. Stover, H. Nguyen

  • 144 bolometers

  •  = 1.1, 2.1 mm

  • 300 mK

CU

Caltech

JPL

Cardiff

Thanks to Sunil for some graphics in this lecture!


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Bolocam

The reality of sky noise (a must read for theorists)

“Average” subtraction takes out 90% of the noise, but we need >99% with retention of large-scale structure

Bolocam is a bolometer-array pioneer and the other groups are looking to us; we’re only in the lead by ~12 months!(this part is for you, Andrew)

Residual noise and itsy-bitsy SZ signal!

“White” noise: ultimate sky subtraction


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Imminent MM-Wave Experiments

High-l Anisotropies

Nils


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References

  • An excellent review from an observer’s perspective and the source of some of the graphics in this lecture: “Cosmology with the Sunyaev-Zel’dovich Effect”, Carlstrom, Holder, & Reese, ARAA, 2002, Vol. 40, pp. 643-680

    • H0:

    • Cluster mass fraction:

    • Cluster peculiar velocities:


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Long-Term Future Work

Probing the physics of galaxy cluster evolution

Hallman & Burns, et al.