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The Sunyaev-Zel’dovich Effect

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

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

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

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

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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!

  18. Some Questions • What are the tradeoffs between 30 GHz (1 cm) and 150/270 GHz (2mm/1mm) observations? • Clearly, we need both.

  19. 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

  20. 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

  21. Bolocam Detectors Incoming Photons Absorber Weak Thermal Link Q Si3N4 micromesh “spider web” bolometer JPL Micro Devices Lab Bath (T ≤ 270 mK)

  22. 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

  23. 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!)

  24. 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!

  25. 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

  26. Imminent MM-Wave Experiments High-l Anisotropies Nils

  27. 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:

  28. Long-Term Future Work Probing the physics of galaxy cluster evolution Hallman & Burns, et al.

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