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 CMB discovered in 1964 by Penzias and Wilson COBE 1989: perfect blackbody to 1/10 5, primary anisotropies measured However, in 1970 Sunyaev & Zel’dovich predicted the SZ effect: secondary anisotropies in the CMB T CMB = K

Physics of the SZ Effect Mechanism & Thermal Effect last scattering surface z ~ 1100 CMB photons T = (1 + z) 2.725K galaxy cluster with hot ICM z ~ scattered photons (hotter) observer z = 0 Sunyaev & Zeldovich (1970) Spectral shift CMB photons have a ~1% chance of inverse Compton scattering off of the ICM electrons; photon number is conserved

Physics of the SZ Effect Functional Form Temperature shift proportional to the gas pressure, n e T e, & mass  dl CMB photon energies boosted by ~kT e /(m e c 2 ) kT e ~ 10 keV, Te ~ 10 8 K  relativistic x = h /(kT e ) f(x) is the spectral dependence Notice that the temperature shift is redshift independent  unbiased surveys for clusters y parameter

Physics of the SZ Effect The Kinetic Effect: a Doppler boost from the peculiar velocity of the cluster Spectral distortion: Kinetic effect is small Null in thermal  measure kinetic Increment Decrement

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

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: T 2 – power usually measured as an excess variance above the noise, C l is per l – there are more independent multipoles at high l Dashed and dotted lines are models The signals are small: ~ GHz, ~ GHz Tentative detections so far (more on this Friday) Green is 30 GHz, or 1 cm Pink is 150 GHz, or 2 mm

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

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

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

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

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.

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.

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.

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.

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.

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!

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

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…) The sky over Mauna Kea Emission = 1 - Transmission 300  m 1 mm2 mm cm band Bolocam

Physics of the SZ Effect The Angular Power Spectrum Green is 30 GHz, or 1 cm Pink is 150 GHz, or 2 mm We need more high-l data!

Si 3 N 4 micromesh “spider web” bolometer JPL Micro Devices Lab Absorber Weak Thermal Link Bath (T ≤ 270 mK) Q Incoming Photons Bolocam Detectors

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 kilometer 1. 1 Anonymous In 1878, Samuel Pierpont Langley invented the bolometer. Bolocam Bolometers

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 kilometer 1. 1 Anonymous In 1878, Samuel Pierpont Langley invented the bolometer. 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 time 2. 2 (In good weather!) Bolocam Bolometers

Focal Plane Bolometer Array 5 in. 144 bolometers = 1.1, 2.1 mm 300 mK CSO CU Caltech JPL Cardiff Cryostat 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 Bolocam Instrument Thanks to Sunil for some graphics in this lecture!

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) “White” noise: ultimate sky subtraction Residual noise and itsy-bitsy SZ signal!

Imminent MM-Wave Experiments High-l Anisotropies Nils

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 H0: Cluster mass fraction: Cluster peculiar velocities:

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