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The microwave background radiation and the Sunyaev-Zel’dovich effect

The microwave background radiation and the Sunyaev-Zel’dovich effect. Mark Birkinshaw. Outline. The microwave background The origin of the SZ effect SZ observations today Cluster structures and SZ effects Cosmology and SZ effects AMiBA and OCRA Summary. 1. The microwave background.

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The microwave background radiation and the Sunyaev-Zel’dovich effect

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  1. The microwave background radiation and the Sunyaev-Zel’dovich effect Mark Birkinshaw

  2. Outline • The microwave background • The origin of the SZ effect • SZ observations today • Cluster structures and SZ effects • Cosmology and SZ effects • AMiBA and OCRA • Summary Mark Birkinshaw, U. Bristol

  3. 1. The microwave background • Provides an intense background thermal radiation • illuminates foreground structures • Has significant structure itself • limits “shadowology” • Has polarization structure • limits foreground polarization studies Mark Birkinshaw, U. Bristol

  4. COBE/FIRAS spectrum FIRAS results: T = 2.728 ± 0.002 K, |y| < 15  10-6, || < 9  10-5 (Fixsen et al. 1996) Mark Birkinshaw, U. Bristol

  5. COBE/FIRAS+DMR dipole FIRAS and DMR measured the dipole: amplitude = 3.372 ± 0.007 mK direction (l,b) = (264.14° ± 0.15°, 48.26° ± 0.15°) (FIRAS values, consistent with DMR, but more precise) Can ignore deviation from monopole temperature. Mark Birkinshaw, U. Bristol

  6. BOOMERanG power spectrum Predicted power spectra (MAP errors) Hu & White (1997) Temperature power spectrum BOOMERanG Netterfield et al. (2002) Mark Birkinshaw, U. Bristol

  7. Power spectrum interpretation • Peak locations show Universe is flat • k = –0.02 ± 0.06 • Fluctuations close to Harrison-Zel’dovich • ns = 0.96 ± 0.10 • Peak heights give matter contents • b = (0.022 ± 0.004) h2 • CDM = (0.13 ± 0.05) h2 • Cosmological concordance still good Netterfield et al. (2002) Mark Birkinshaw, U. Bristol

  8. Polarization E-mode polarization detection DASI Mark Birkinshaw, U. Bristol

  9. 2. The origin of the SZ effect Clusters of galaxies contain extensive hot atmospheres Te 6 keV np 103 protons m-3 L  1 Mpc 2 Mpc Mark Birkinshaw, U. Bristol

  10. Inverse-Compton scatterings • Cluster atmospheres scatter photons passing through them. Central iC optical depth tenp sT L 10-2 • Each scattering changes the photon frequency by a fraction    Mark Birkinshaw, U. Bristol

  11. Single-scattering frequency shift P1(s) s = log() 5 keV 15 keV Mark Birkinshaw, U. Bristol

  12. Thermal SZ effect • The fractional intensity change in the background radiation I/I = -2 (n/n)te 10-4 • Effect in brightness temperature terms is DTRJ = -2 Tr(n/n)te -300 K • Brightness temperature effect, DTRJ, is independent of redshift Mark Birkinshaw, U. Bristol

  13. Microwave background spectrum I  Mark Birkinshaw, U. Bristol

  14. Spectrum of thermal effect • effect caused by small frequency shifts, so spectrum related to gradient of CMB spectrum • zero at peak of CMB spectrum Mark Birkinshaw, U. Bristol

  15. Temperature sensitivity • Te < 5 keV: e– non-relativistic, effect independent of Te • Te > 5 keV: enough e– relativistic that spectrum is function of Te • Te > 1 GeV: spectrum independent of Te, negative of CMB (non-thermal SZ effect) 5 keV 15 keV Mark Birkinshaw, U. Bristol

  16. Spectrum of kinematic effect • effect caused by reference frame change, related to CMB spectrum • maximum at peak of CMB spectrum • negative of CMB spectrum Mark Birkinshaw, U. Bristol

  17. Attributes of SZ effect • TRJ is a redshift-independent function of cluster properties only. If the gas temperature is known, it is aleptometer • TRJ contains a weak redshift-independent kinematic effect, it is aradial speedometer • TRJ has a strong association with rich clusters of galaxies, it is amass finder • TRJ has polarization with potentially more uses, but signal is tiny Mark Birkinshaw, U. Bristol

  18. 3. SZ observations today • Interferometers: Ryle, BIMA, OVRO, … • Structural information • Baseline range • Single-dish radiometers: 40-m, Corona, … • Speed • Systematic effects • Bolometers: SuZIE, MAD, ACBAR, … • Frequency coverage • Weather Mark Birkinshaw, U. Bristol

  19. Interferometers • restricted angular dynamic range set by baseline and antenna size • good rejection of confusing radio sources Abell 665 model, VLA observation Mark Birkinshaw, U. Bristol

  20. Interferometers • good sky and ground noise rejection because of phase data • long integrations and high signal/noise possible • 10 years of data, tens of cluster maps • SZ detected for cluster redshifts from 0.02 (VSA) to 1.0 (BIMA) Mark Birkinshaw, U. Bristol

  21. Ryle telescope • first interferometric map • Abell 2218 • brightness agrees with single-dish data • limited angular dynamic range Figure from Jones et al. 1993 Mark Birkinshaw, U. Bristol

  22. BIMA/OVRO • limited angular dynamic range • high signal/noise (with enough tint) • clusters easily detectable to z 1 Figure from Carlstrom et al. 1999 Mark Birkinshaw, U. Bristol

  23. Single-dish radiometers • Potentially fast way to measure SZ effects of particular clusters • Multi-beams better than single beams at subtracting atmosphere, limit cluster choice • Less fashionable now than formerly: other techniques have improved faster • New opportunities: e.g., GBT Mark Birkinshaw, U. Bristol

  24. OVRO 40-m • Crude mapping possible • Difficulties with variable sources • Relatively fast for detections of SZ effects Figure from Birkinshaw 1999 Mark Birkinshaw, U. Bristol

  25. Viper telescope at the South Pole • 1998-2000: 1-pixel receiver (Corona); 40 GHz • Since 2001: 16-pixel bolometer (ACBAR); 150, 220, 275 GHz • Dry air, 3º chopping tertiary, large ground shield • Excellent for SZ work Mark Birkinshaw, U. Bristol

  26. 1999 Corona observation of A3667 • A 3667: brightest z < 0.1 REFLEX cluster far enough South for Viper • 3.6 º 2.0º raster scan shows cold spot at the X-ray centroid and hot regions at the radio halo • H0=64 km s-1 Mpc-1 Cantalupo, Romer, et al. Mark Birkinshaw, U. Bristol

  27. Bolometers • Should be fast way to survey for SZ effects • Wide frequency range possible on single telescope, allowing subtraction of primary CMB structures • Atmosphere a problem at every ground site • Several experiments continuing, SuZIE, MITO, ACBAR, BOLOCAM, etc. Mark Birkinshaw, U. Bristol

  28. SCUBA 850 µm images: SZ effect measured in one; field too small Mark Birkinshaw, U. Bristol

  29. MITO • MITO experiment at Testagrigia • 4-channel photometer: separate components • 17 arcmin FWHM • Coma cluster detection Figure from De Petris et al. 2002 Mark Birkinshaw, U. Bristol

  30. ACBAR cluster observations • ACBAR produces simultaneous 3-frequency images, subtracts primary CMB fluctuations • Observing complete luminosity-limited sample (~10 REFLEX clusters) with Viper • XMM/Chandra and weak lensing data • AS1063, 0658-556, A3667, A3266, A3827, A3112, A3158 already imaged Romer, Gomez, Peterson, Holzapfel, Ruhl et al. Mark Birkinshaw, U. Bristol

  31. 4. Cluster structures and SZ effects • Integrated SZ effects • total thermal energy content • total hot electron content • SZ structures • not as sensitive as X-ray data • need for gas temperature • Radial velocity of clusters via kinematic effect • Mass structures and relationship to lensing Mark Birkinshaw, U. Bristol

  32. Integrated SZ effects • Total SZ flux density Thermal energy content immediately measured in redshift-independent way Virial theorem then suggests SZ flux density is direct measure of gravitational potential energy Mark Birkinshaw, U. Bristol

  33. Integrated SZ effects • Total SZ flux density If have X-ray temperature, then SZ flux density measures electron count, Ne (and hence baryon count) Combine with X-ray derived mass to get fb Mark Birkinshaw, U. Bristol

  34. Radial velocity • Kinematic effect separable from thermal SZ effect because of different spectrum • Confusion with primary CMB fluctuations limits velocity accuracy to about 150 km s-1 • If velocity substructure in atmospheres, even less accuracy will be possible • Statistical measure of velocity distribution of clusters as a function of redshift in samples Mark Birkinshaw, U. Bristol

  35. Cluster velocities Need • good SZ spectrum • X-ray temperature Confused by CMB structure Sample  vz2 Three clusters so far, vz  1000 km s A 2163; figure from LaRoque et al. 2002. Mark Birkinshaw, U. Bristol

  36. SZ effect structures • Currently only crudely measured by any method (restricted angular dynamic range) • X-ray based structures superior • Structure should be more extended in SZ than in X-ray because of nerather than ne2dependence, so good SZ structure should extend out further and show more about halo Mark Birkinshaw, U. Bristol

  37. Cluster distances and masses DA = 1.36  0.15 Gpc H0 = 68  8  18 km s-1 Mpc-1 Mtot(250 kpc) = (2.0  0.1)  1014 M XMM+SZ Mtot(250 kpc) = (2.7  0.9)  1014 M lensing Mgas(250 kpc) = (2.6  0.2)  1013 M XMM+SZ CL 0016+16 with XMM; Worrall & Birkinshaw 2002 Mark Birkinshaw, U. Bristol

  38. 5. Cosmology and SZ effects • Cosmological parameters • cluster-based Hubble diagram • cluster counts as function of redshift • Cluster evolution physics • evolution of cluster atmospheres via cluster counts • evolution of radial velocity distribution • evolution of baryon fraction • Microwave background temperature elsewhere in Universe Mark Birkinshaw, U. Bristol

  39. Cluster Hubble diagram X-ray surface brightness X  ne2 Te½ L SZ effect intensity change I  ne Te L Eliminate unknown ne • L  I2 X1 Te3/2  H0  XI2 Te3/2  Mark Birkinshaw, U. Bristol

  40. Hubble diagram • poor leverage for other parameters • need many clusters at z > 0.5 • need reduced random errors • ad hoc sample • systematic errors Mark Birkinshaw, U. Bristol

  41. Critical assumptions • spherical cluster (or randomly-oriented sample) • knowledge of density and temperature structure to get form factors • clumping negligible • selection effects understood need orientation-independent sample Mark Birkinshaw, U. Bristol

  42. SZ effect surveys • SZ-selected samples needed for reliable cosmology • almost mass limited • flat redshift response • X-ray samples • SZ follow-ups for ROSAT-derived samples • selects more stratified clusters • Optical samples • much used in past, line-of-sight confusion problem Mark Birkinshaw, U. Bristol

  43. Distribution of central SZ effects • Mixed sample of 37 clusters • OVRO 40-m data, 18.5 GHz • No radio source corrections • 40% of clusters have observable T < –100 K Mark Birkinshaw, U. Bristol

  44. Cluster counts and cosmology dN/dz Cluster counts and redshift distribution provide strong constraints on 8, m, and cluster heating. Wm=1.0 WL=0 s8=0.52 Wm=0.3 WL=0.7 s8=0.93 Wm=0.3 WL=0 s8=0.87 z Figure from Fan & Chiueh 2000 Mark Birkinshaw, U. Bristol

  45. Baryon mass fraction SRJ Ne Te Total SZ flux  total electron count  total baryon content. Compare with total mass (from X-ray or gravitational lensing)  baryon fraction b/m Figure from Carlstrom et al. 1999. Mark Birkinshaw, U. Bristol

  46. Cluster velocities Confused by CMB structure, cluster velocity errors of 150 km s-1 at best (currently worse) Sample could give z2(z): dynamics A 2163; figure from LaRoque et al. 2002. Mark Birkinshaw, U. Bristol

  47. Microwave background temperature • Ratio of SZ effects at two different frequencies is a function of CMB temperature (with slight dependence on Te and cluster velocity) • So can use SZ effect spectrum to measure CMB temperature at distant locations and over range of redshifts • Test T  (1 + z) Mark Birkinshaw, U. Bristol

  48. Microwave background temperature • Test T  (1 + z) • SZ results for two clusters plus results from molecular excitation Battistelli et al. (2002) Mark Birkinshaw, U. Bristol

  49. 6. AMiBA and OCRA • Many new SZ facilities under development • bolometers and interferometers most popular • south pole, Chile, Mauna Kea, Tenerife • AMiBA • ASIAA/NTU development • operational in 2003 • OCRA • -p operational in 2003, -F in 2005 Mark Birkinshaw, U. Bristol

  50. New SZ facilities • AMiBA • OCRA (-p, -F, -) • AMI • MAP • Planck • SuZIE-n • BOLOCAM • CARMA • ALMA • SZA • ACBAR • MITO/MAD • APEX • etc., etc., etc. Mark Birkinshaw, U. Bristol

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