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SZ/CMB models: Q-band science

SZ/CMB models: Q-band science. Mark Birkinshaw University of Bristol. 1. Simple observables: shape. SZ effects – from inverse-Compton scattering by hot electrons on cold CMB photons.

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SZ/CMB models: Q-band science

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  1. SZ/CMB models:Q-band science Mark Birkinshaw University of Bristol

  2. 1. Simple observables: shape SZ effects – from inverse-Compton scattering by hot electrons on cold CMB photons. Thermal SZ effect – los amplitude  Comptonization parameter, ye, the dimensionless electron temperature weighted by the scattering optical depth Mark Birkinshaw, U. Bristol

  3. Simple observables: shape For a simple isothermal  model • typical central value ye0  10-4 • SZ effect has angular size about 3 × X-ray angular size for  ~ 0.7 (typical for rich clusters) • at z = 0.2, θc~ 1 arcmin for rich cluster Mark Birkinshaw, U. Bristol

  4. Simple observables: spectrum • spectrum related to gradient of CMB spectrum • zero near CMB peak (about 220 GHz) • flux density effect small at long λ Q Mark Birkinshaw, U. Bristol

  5. Simple observables: spectrum If the cluster is moving, then in the cluster frame the CMB is anisotropic. Scattering isotropizes it by an amount  evz, giving kinematic SZE. Angular shape same as thermal SZ effect, if cluster is isothermal. Spectrum differs from thermal SZ effect, but same shape as the spectrum of primordial CMB fluctuations, so velocity information is obtained contaminated by the (lensed) primordial CMB. Mark Birkinshaw, U. Bristol

  6. Simple observables: kinematic SZE • spectrum related to gradient of CMB spectrum • no zero • small compared to thermal effect at low frequency • flux density effect small at long λ • confused by primordial structure Q Mark Birkinshaw, U. Bristol

  7. 2. Simple observations • Prime focus: • single on-axis feed • symmetrical dual feeds Simplest: single-dish radiometers/radiometer arrays. • Secondary focus: • single on-axis feed • symmetrical dual feeds • array of feeds (large focal plane) • e.g., OCRA series Mark Birkinshaw, U. Bristol

  8. Sample studies (X-ray/optical selection) Lancaster et al. (2009; in preparation) • 34 highest LX clusters from ROSAT BCS (Ebeling et al. 1998) at z > 0.2 • ‘fair’ sample with few biases • Complete subset of 18 with Chandra data • Study scaling relations: decode surveys • Statistically useful cluster parameters • OCRA-p on Toruń 32-m (OCRA-F now, OCRA-C possible) • noise~ 0.4 mJy [less than 1 hour/cluster] Mark Birkinshaw, U. Bristol

  9. Source contamination SZ effects evident in most clusters before source correction – compare cluster and trail statistics. Uncorrected: lose 20% of clusters. Corrected (GBT): lose 10% of clusters (lose 5% of trails). Mark Birkinshaw, U. Bristol

  10. Scaling relation: flux density/X-ray kT consistent with expected 3/2 scaling relation Mark Birkinshaw, U. Bristol

  11. Next step: blind survey Potential field: XMM-LSS. Survey blind in SZ, provides parallel X-ray, lensing, IR data. Too far south for Toruń: accessible to AMiBA. Mark Birkinshaw, U. Bristol

  12. AMiBA-13 Partially-completed AMiBA-13 interferometer on Mauna Loa (baselines to 6.5 m). Larger antennas than in first AMiBA season. 90 GHz: would need a larger system at 30 GHz. Mark Birkinshaw, U. Bristol

  13. SZ effect confusion on CMB Figure from Molnar & Birkinshaw 2000 thermal SZ kinematic SZ RS effect Mark Birkinshaw, U. Bristol

  14. Sensitivity of radiometer Single-dish and interferometers need to use switching strategies or extra filtering. Beam-switching + position-switching, or scanning for single dishes. Multi-field differencing or fringe rate filtering for interferometers. (N > 1), but TA doesn’t reduce with time as -1/2 after some time: unsteady gain and Tsysetc. Mark Birkinshaw, U. Bristol

  15. Simple observations: z dependence Angular size and separation of beams leads to redshift dependent efficiency Shape of curve shows redshift of maximum signal, long plateau. Similar for all types of observation. Mark Birkinshaw, U. Bristol

  16. Simple observations: interferometers SZA (2008) Mark Birkinshaw, U. Bristol

  17. Simple observations: interferometer sensitivity Sensitivity of interferometer Ncorr = number of antenna-antenna correlations used in making synthesized beam (solid angle synth). source = solid angle of source. Built-in rejection of many systematic errors. Mark Birkinshaw, U. Bristol

  18. Simple observations: angular dynamic range • restricted angular dynamic range set by baseline and antenna size • good rejection of confusing radio sources (use long baselines) • even tightly packed arrays trade sensitivity for resolution available baselines Abell 665 model, VLA observation Mark Birkinshaw, U. Bristol

  19. Simple observations: interferometer maps • restricted angular dynamic range • high signal/noise (long integration possible) • clusters easily detectable to z 1 • better for structure studies? Carlstrom et al. 1999 Mark Birkinshaw, U. Bristol

  20. 3. Simple science results • Integrated SZ effects • total thermal energy content • total hot electron content • SZ structures • not as sensitive as X-ray data • need for gas temperature • Mass structures and relationship to lensing • Radial peculiar velocity via kinematic effect Mark Birkinshaw, U. Bristol

  21. Simple science results: integrated SZE Total SZ flux density Thermal energy content immediately measured in redshift-independent way Virial theorem: SZ flux density should be good measure of gravitational potential energy Mark Birkinshaw, U. Bristol

  22. Simple science results: integrated SZE Total SZ flux density With X-ray temperature, SZ flux density measures electron count, Ne (hence baryon count) and total gas mass Combine with X-ray derived mass to get fb Mark Birkinshaw, U. Bristol

  23. Some rough Q-band numbers These total flux densities are integrated out to the virial radius: most observations cannot go out that far. Note that the total flux densities are highly distance dependent – the detectable signals in a single beam (radiometer/interferometer) are less so because of the z-dependence of the efficiency. Mark Birkinshaw, U. Bristol

  24. Simple science results: SZE and lensing Weak lensing measures ellipticity field e, and so Surface mass density as a function of position can be combined with SZ effect map to give a map of fb SRJ/ Mark Birkinshaw, U. Bristol

  25. Simple science results: total, gas masses Inside 250 kpc: XMM +SZ Mtot = (2.0  0.1)1014 M Lensing Mtot = (2.7  0.9)1014 M XMM+SZ Mgas = (2.6  0.2)  1013 M CL 0016+16 with XMM Worrall & Birkinshaw 2003 Mark Birkinshaw, U. Bristol

  26. z=0.68 z=0.68 z=0.58 z=0.14 z=0.25 z=0.73 z=0.29 z=0.14 z=0.25 Lensing and the thermal SZ effect pixel data from simulations 4.25 clusters identified in simulations × Noise dominated region 4.5 Mark Birkinshaw, U. Bristol

  27. Simple science results: vz • Kinematic effect separable from thermal SZE by different spectrum • Confusion with primary CMB fluctuations limits vz accuracy (typically to 150 km s-1) • Velocity substructure in atmospheres will reduce accuracy further • Statistical measure of velocity distribution of clusters as a function of redshift in samples Mark Birkinshaw, U. Bristol

  28. 3. Simple science results: vz Need • good SZ spectrum • X-ray temperature Confused by CMB structure Sample  vz2 Errors  1000 km s so far A 2163; figure from LaRoque et al. 2002. Mark Birkinshaw, U. Bristol

  29. 3. Simple science results: cosmology • 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

  30. 3. Simple science results: cluster distances X-ray surface brightness SZE intensity change Eliminate unknown ne to get cluster size L, and hence distance or H0 Mark Birkinshaw, U. Bristol

  31. Simple science results: cluster distances CL 0016+16 DA = 1.36  0.15 Gpc H0 = 68  8  18 km s-1 Mpc-1 Worrall & Birkinshaw 2003 Mark Birkinshaw, U. Bristol

  32. Simple science results: cluster Hubble diagram • poor leverage for other parameters • need many clusters at z > 0.5 • need reduced random errors • ad hoc sample • systematic errors Carlstrom, Holder & Reese 2002 Mark Birkinshaw, U. Bristol

  33. Simple science results: SZE surveys • SZ-selected samples • almost mass limited and orientation independent • Large area surveys • 1-D interferometer surveys slow, 2-D arrays better • radiometer arrays fast, but radio source issues • bolometer arrays fast, good for multi-band work • Survey in regions of existing X-ray/optical surveys • Expect SZ to be better than X-ray at high z Mark Birkinshaw, U. Bristol

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

  35. 4. More complicated observables • Detailed structures • Gross mass model • Clumping • Shocks and cluster substructures • Detailed spectra • Temperature-dependent/other deviations from Kompaneets spectrum • CMB temperature • Polarization • Multiple scatterings • Velocity term Mark Birkinshaw, U. Bristol

  36. Detailed structures Clumping induced by galaxy motions, minor mergers, etc. affects the SZE/X-ray relationship More extreme structures caused by major mergers, associated with shocks, cold fronts Further SZE (density/temperature-dominated) structures associated with radio sources (local heating), cooling flows, large-scale gas motions (kinematic effect). SZ effects are more relatively sensitive to outer parts of clusters than X-ray surface brightness. Mark Birkinshaw, U. Bristol

  37. Detailed structures J0717.5+3745 z = 0.548 Clearly disturbed, shock-like substructure, filament What will SZ image look like? Mark Birkinshaw, U. Bristol

  38. Detailed structures Bullet cluster, Laboca (extensively filtered). High-frequency structure affected by bright point source Many other point sources; SZ effect also detected – easier in Q band, probably. (Lopez-Cruz et al.) Mark Birkinshaw, U. Bristol

  39. Detailed spectra • 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 TCMB  (1 + z) Battistelli et al. (2002) Mark Birkinshaw, U. Bristol

  40. Detailed spectra • for low-Te gas effect is independent of Te • Te > 5 keV, spectrum is noticeable function of Te • non-thermal effect (high energies) gives distortion • multiple scatterings give another distortion • hard to measure 5 keV 15 keV Mark Birkinshaw, U. Bristol

  41. Polarization Polarization signals are O(z) or O(e) smaller than the total intensity signals: this makes them extremely hard to measure. Interferometers help by rejecting much of the resolved signal, since some of the polarization signal has smaller angular size than I. Still need excellent common-mode rejection to remove systematic errors in polarization. Mark Birkinshaw, U. Bristol

  42. 5. Requirements on observations Mark Birkinshaw, U. Bristol

  43. Requirements on observations Mark Birkinshaw, U. Bristol

  44. Requirements on observations Mark Birkinshaw, U. Bristol

  45. 6. Status of SZ effects • Hundreds of cluster detections • many high significance (> 10) detections • multi-telescope confirmations • poor interferometer maps, structures usually from X-rays • Spectral measurements still rudimentary • no kinematic effect detections • Preliminary blind and semi-blind surveys • a few detections (not at Q band, yet) Mark Birkinshaw, U. Bristol

  46. Status at the time of early ALMA • 10 × more cluster detections • Planck catalogue, low-z not yet available • high-resolution surveys (AMiBA-13, SZA, SPT, APEX-SZ, etc.; Q-band selected fraction?) • About 100 images with > 100 resolution elements • mostly interferometric, tailored arrays, 10 arcsec FWHM • some bolometric maps, 15 arcsec FWHM • angular dynamic range, structure indications poor • A few integrated spectral measurements • Still confusion limited • Still problems with absolute calibration Mark Birkinshaw, U. Bristol

  47. ALMA possibilities • Q band good for SZ studies • ALMA: 1 μJy in 10 arcsec FWHM over 145 arcsec primary beam in 12 hours: cluster substructure mapping with main array (loses largest scales) • quality of mosaics? • 7-m antennas in compact configuration more effective on angular scales of most interest • Blind surveys using ALMA band-1 not likely – wrong angular scales (OCRA-F/AMiBA/APEX-SZ/…) • Fortunately, Chandra and XMM-Newton still working Mark Birkinshaw, U. Bristol

  48. Possible SZ unique studies • Hot outflows around ionizing objects at recombination (or later) may show kinematic with little thermal SZ. • SZ spectral inversion into electron distribution function – 100-400 GHz range critical. • Information on developing cluster velocity field. • Non-thermal SZ effect in large radio sources to test equipartition (c.f., X-ray inverse-Compton studies). Leverage on relativistic electron populations? Mark Birkinshaw, U. Bristol

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