The Sunyaev-Zel’dovich effect: background and issues Opening invited review for meeting “The Sunyaev-Zel’dovich effect and ALMA” IAS, Orsay – 7-8 April 2005 1. Simple observables based on simple cluster models 2. Simple observations 3. Simple science results 4. More complicated observables 5. Requirements on observations 6. Status at the time of ALMA Mark Birkinshaw University of Bristol

1. Simple observables: shape The SZ effects are the results of inverse-Compton scattering by hot electrons on cold CMB photons. The principal (thermal) SZ effect has an amplitude proportional to the Comptonization parameter, ye, the dimensionless electron temperature weighted by the scattering optical depth 7 April 2005 Mark Birkinshaw, U. Bristol

1. Simple observables: shape For a simple isothermal  model Typical central value ye0  10-4 SZE has larger angular size than X-ray image and weaker dependence on  7 April 2005 Mark Birkinshaw, U. Bristol

1. Simple observables: spectrum For clusters which aren’t too hot, or at low frequency, the thermal SZE has the Kompaneets spectrum x is the dimensionless frequency, h/kBTCMB = 0.0186(/GHz) I0 is the specific intensity scale from the thermal SZE 7 April 2005 Mark Birkinshaw, U. Bristol

1. Simple observables: spectrum spectrum related to gradient of CMB spectrum zero near peak of CMB spectrum (about 220 GHz) 7 April 2005 Mark Birkinshaw, U. Bristol

1. Simple observables: kinematic SZE If the cluster is moving, then in the cluster frame the CMB is anisotropic. Scattering isotropizes it by an amount  evz, giving kinematic SZE Same as spectrum of primordial CMB fluctuations: TCMB change. 7 April 2005 Mark Birkinshaw, U. Bristol

1. Simple observables: kinematic SZE spectrum related to gradient of CMB spectrum no zero small compared to thermal effect at low frequency confused by primordial structure 7 April 2005 Mark Birkinshaw, U. Bristol

2. Simple observations Prime focus: single on-axis feed symmetrical dual feeds Secondary focus: single on-axis feed symmetrical dual feeds array of feeds (large focal plane) Simplest: single-dish radiometers/radiometer arrays. 7 April 2005 Mark Birkinshaw, U. Bristol

2. Simple observations: radiometer sensitivity Always observe with beam-switching + position-switching, or scanning, or some other strategy to reduce systematic errors. Sensitivity expected to be (N > 1), but TA doesn’t reduce with time as -1/2 after some limiting time, because gain and Tsys are unsteady. 7 April 2005 Mark Birkinshaw, U. Bristol

2. 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 7 April 2005 Mark Birkinshaw, U. Bristol

2. Simple observations: radiometer results fast at measuring integrated SZ effect of given cluster multi-beam limits choice of cluster, but subtracts sky well radio source worries less used since early 1990s new opportunities, e.g. GBT, with radiometer arrays Birkinshaw 1999 7 April 2005 Mark Birkinshaw, U. Bristol

2. Simple observations: interferometers OVRO array in compact configuration (old site). 7 April 2005 Mark Birkinshaw, U. Bristol

2. 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. 7 April 2005 Mark Birkinshaw, U. Bristol

2. Simple observations: interferometer baselines restricted angular dynamic range set by baseline and antenna size good rejection of confusing radio sources (can use long baselines) available baselines Abell 665 model, VLA observation 7 April 2005 Mark Birkinshaw, U. Bristol

2. Simple observations: interferometer maps First interferometric detection of SZE: Ryle telescope, Abell 2218 Jones et al. (1993) 7 April 2005 Mark Birkinshaw, U. Bristol

2. Simple observations: interferometer maps restricted angular dynamic range high signal/noise (long integration possible) clusters easily detectable to z  1 Carlstrom et al. 1999 7 April 2005 Mark Birkinshaw, U. Bristol

2. Simple observations: interferometer maps VSA: low-z clusters About 100 hours/map High signal/noise detection Apparent noise is confusion from CMB primordial fluctuations – limitation of all single-frequency work Lancaster et al. (2004; astro-ph/0405582) 7 April 2005 Mark Birkinshaw, U. Bristol

2. Simple observations: bolometers A good alternative is bolometric observation using an array: e.g., BOLOCAM on CSO; ACBAR on Viper. Issues to do with the stability of the atmosphere. mm-wave data – good for looking at spectrum. 7 April 2005 Mark Birkinshaw, U. Bristol

2. Simple observations: bolometer maps A 3266: z = 0.06 VIPER +ACBAR Images at 150, 220, 275 GHz, 5 arcmin FWHM Remove CMB to leave thermal SZE (bottom right) Gómez et al. 2003 7 April 2005 Mark Birkinshaw, U. Bristol

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 7 April 2005 Mark Birkinshaw, U. Bristol

3. 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 7 April 2005 Mark Birkinshaw, U. Bristol

3. Simple science results: integrated SZE 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 7 April 2005 Mark Birkinshaw, U. Bristol

3. Simple science results: SZE structures Only crudely measured so far Relatively more sensitivity to outer parts of clusters than X-ray data Angular dynamic range issue: limitation of array sizes (radiometer, interferometer, bolometer), and CMB confusion Will need sensitivity at Jy level on 10 arcsec to 120 arcsec scales 7 April 2005 Mark Birkinshaw, U. Bristol

3. 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/ 7 April 2005 Mark Birkinshaw, U. Bristol

3. 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 7 April 2005 Mark Birkinshaw, U. Bristol

3. 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 7 April 2005 Mark Birkinshaw, U. Bristol

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. 7 April 2005 Mark Birkinshaw, U. Bristol

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 7 April 2005 Mark Birkinshaw, U. Bristol

3. Simple science results: cluster Hubble diagram X-ray surface brightness SZE intensity change Eliminate unknown ne to get cluster size L, and hence distance or H0 7 April 2005 Mark Birkinshaw, U. Bristol

3. Simple science results: cluster distances DA = 1.36  0.15 Gpc H0 = 68  8  18 km s-1 Mpc-1 Worrall & Birkinshaw 2003 7 April 2005 Mark Birkinshaw, U. Bristol

3. 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 7 April 2005 Mark Birkinshaw, U. Bristol

3. 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 7 April 2005 Mark Birkinshaw, U. Bristol

3. Simple science results: SZE sky SZ sky predicted using structure formation code (few deg2, y = 0 – 10-4) Primordial fluctuations ignored Cluster counts strong function of cosmological parameters and cluster formation physics. 7 April 2005 Mark Birkinshaw, U. Bristol

3. Simple science results: SZE sky See talks of Stefano Borgani Scott Kay Antonio da Silva Lauro Moscardini Jim Bartlett Joseph Silk 7 April 2005 Mark Birkinshaw, U. Bristol

3. 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. 7 April 2005 Mark Birkinshaw, U. Bristol

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 7 April 2005 Mark Birkinshaw, U. Bristol

4. More complicated observables: 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 likely), cooling flows, large-scale gas motions (kinematic effect). 7 April 2005 Mark Birkinshaw, U. Bristol

4. More complicated observables: detailed structures J0717.5+3745 z = 0.548 Clearly disturbed, shock-like substructure, filament What will SZ image look like? 7 April 2005 Mark Birkinshaw, U. Bristol

4. More complicated observables: detailed structures See talks by Monique Arnaud Doris Neumann Steen Hansen Tetsu Kitayama Christoph Pfrommer Andrea Lapi 7 April 2005 Mark Birkinshaw, U. Bristol

4. More complicated observables: 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) 7 April 2005 Mark Birkinshaw, U. Bristol

4. More complicated observables: 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 15 keV 5 keV 7 April 2005 Mark Birkinshaw, U. Bristol

4. More complicated observables: detailed spectra See talks by Francesco Melchiorri Björn Schaeffer Diego Herranz Sergio Colafrancesco Jens Chluba 7 April 2005 Mark Birkinshaw, U. Bristol

4. More complicated observables: 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 7 April 2005 Mark Birkinshaw, U. Bristol

4. More complicated observables: polarization See talks by Doris Neumann Asantha Cooray Jens Chluba 7 April 2005 Mark Birkinshaw, U. Bristol

5. Requirements on observations Use Size (mK) Critical issues Energetics 0.50 Absolute calibration Baryon count Absolute calibration; isothermal/spherical cluster; gross model Gas structure Beamshape; confusion Mass distribution Absolute calibration; isothermal/spherical cluster Hubble diagram Absolute calibration; gross model; clumping; axial ratio selection bias 7 April 2005 Mark Birkinshaw, U. Bristol

5. Requirements on observations Use Size (mK) Critical issues Blind surveys 0.10 Gross model; confusion Baryon fraction evolution Absolute calibration; isothermal/spherical cluster; gross model CMB temperature Absolute calibration; substructure Radial velocity 0.05 Absolute calibration; gross model; bandpass calibration; velocity substructure 7 April 2005 Mark Birkinshaw, U. Bristol

5. Requirements on observations Use Size (mK) Critical issues Cluster formation 0.02 Absolute calibration Transverse velocity 0.01 Confusion; polarization calibration 7 April 2005 Mark Birkinshaw, U. Bristol

6. Status at the time of ALMA: 2005 Current status About 100 cluster detections high significance (> 10) detections multi-telescope confirmations interferometer maps, structures usually from X-rays Spectral measurements still rudimentary no kinematic effect detections Preliminary blind and semi-blind surveys a few detections 7 April 2005 Mark Birkinshaw, U. Bristol

6. Status at the time of ALMA: 2005-2010 See talks by Rüdiger Kneissl Guo-Chin Liu Katy Lancaster Pierre Cox Frank Bertoldi John Carlstrom Björn Schaefer … and other SZ instrumentation projects 7 April 2005 Mark Birkinshaw, U. Bristol

6. Status at the time of ALMA: 2010 About 5000 cluster detections Most from Planck catalogue, low-z 10% from high-resolution surveys (AMiBA, SZA, BOLOCAM, etc.) About 100 images with > 100 resolution elements Mostly interferometric, tailored arrays, 10 arcsec FWHM Some bolometric maps, 15 arcsec FWHM About 50 integrated spectral measurements Still confusion limited Still problems with absolute calibration 7 April 2005 Mark Birkinshaw, U. Bristol

6. Status at the time of ALMA: ALMA, 2010 ALMA band 1 suitable for SZE 1 microJy in 10 arcsec FWHM over 145 arcsec primary beam in 12 hours Cluster substructure mapping (loses largest scales) Quality of mosaics still uncertain Band 1 is not likely to be available in 2010 Blind surveys using ALMA band-1 not likely – wrong angular scales See talks by Robert Laing, Steve Myers 7 April 2005 Mark Birkinshaw, U. Bristol

6. Status at the time of ALMA: X-ray context: 2010 No XMM or Chandra Constellation-X/XEUS not available Working with archival X-ray surveys X-ray spectra of high-z clusters of relatively poor quality Optical/IR survey follow-up in SZE, or order of follow-ups reversed: SZE before X-ray. 7 April 2005 Mark Birkinshaw, U. Bristol