Mark Birkinshaw University of Bristol

Name: Mark Birkinshaw University of Bristol
Uploaded: 2017-11-29T18:50:39+00:00
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Description: Mark Birkinshaw University of Bristol

Mark Birkinshaw University of Bristol
SZ – overview SZ overview for CMB B-mode and SZ experiment meeting Cambridge, July 2009 Mark Birkinshaw University of Bristol

Mark Birkinshaw, U. Bristol
Thermal SZ effect Photons gain energy, spectrum depressed at low  I  Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

tSZ effect – Kompaneets spectrum
for non-relativistic electrons, effect is independent of Te at Te > 5 keV enough electrons relativistic that spectrum varies at high : relativistic corrections measure mass-weighted Te Kompaneets form useful approximation at low  for all Te 15 keV 5 keV Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

The ye parameter The Comptonization parameter At low frequency the tSZ effect has amplitude ΔTRJ = -2ye  10-4 for the centre of a rich cluster. CMB photons are far from equilibrium with cluster gas after scattering. ye defines the angular shape of the cluster SZ effect – it is a function of position on the sky, measures line-of-sight averaged pressure, and is redshift independent. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

The Ye parameter A survey usually measures an integrated tSZE flux density, proportional to the integrated Comptonization in the survey beam An observation will measure only some fraction of the integrated flux density because of the implicit spatial filtering. Ye is redshift dependent but a strong indicator of cluster binding energy (mass). Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Angular structure X-ray (L), SZ effect (R) ellipsoidal models for Abell 665: note difference in angular structures – tSZ effect is far more extended. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

The kSZ effect If the cluster is moving along the line of sight, then in the cluster frame the CMB is anisotropic. Scattering isotropizes it by an amount  evz, giving kinematic SZE This makes the kinematic effect hard to see against the brighter thermal effect – it’s necessary to use spectral differences to separate the effects. Even then, the kinematic effect is heavily confused by primordial CMB structures – has same spectrum. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

kSZ effect kinematic spectrum related to temperature gradient of CMB spectrum no zero small compared to thermal effect at low frequency confused by primordial structure Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Polarization effects There are three contributions to the polarization signal scattering the quadrupole in the primordial CMB, effect ~ 0.1 K in either the E or B modes and coherent shape across the cluster multiple scatterings inside the cluster, effect ~ 0.1 K in a ring about the cluster centre transverse velocity of the cluster, effect ~ 10× smaller (easier to measure through transverse lensing effect in intensity, ~ 0.1 K) These effects are confused by the cluster lensing the primordial CMB polarization, causing a signal ~ 3 K Spectral and spatial structures of these effects differ, may allow separation, though lensing effect dominates. All effects beyond current capabilities. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Levels of study of SZ effect
First level: detection of integrated effect Complete since mid 1980s 200+ clusters well detected Narrow band of cluster properties (selection effect imposed by sensitivity, resolution) Cluster energy contents, mass measurements, baryon mass fractions, Hubble constant Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

tSZE distribution: X-ray selected clusters
Lancaster et al., in prep. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Scaling relations: tSZ/kTe
Close to self-similar slope. Cluster scaling relation at z ~ 0.2. Mass probe to z > Lancaster et al., in prep. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster energy content
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 Flux density indicates mass and degree of organization of cluster atmosphere. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster energy content
Useful measurement requires absolute calibration of flux density scale – still an issue in radio astronomy at 5% level. Comparisons with galaxy kinematics at 5% level valuable but little work so far. Requires integration over entire cluster – high level of confusion for low-z clusters unless the cluster is mapped and point sources (AGN at cm , star-forming or dusty galaxies at mm ) and primordial CMB are removed Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster baryonic content
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 Redshift-independence of ye should allow baryon content to be measured to large z. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster baryonic content
Effective measurement of electron number in cluster requires absolute calibration of SZ data and adequacy of isothermal model over full SZ extent accurate electron temperature from X-ray Technique avoids assumptions on cluster shape, or hydrostatic equilibrium. Compare with X-ray data to test cluster model. Integral over cluster, subject to confusion problems at low z. Much of SZ effect comes from outer gas where Te is poorly measured in the X-ray. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Baryon mass fraction Inside 250 kpc: XMM +SZ Mtot = (2.0  0.1)1014 M Mgas = (2.6  0.2)  1013 M Combine results: fb = 0.13 ± 0.02 (distance-independent) WMAP: fb = 0.12 ± 0.02 CL with XMM Worrall & Birkinshaw 2003 Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Baryon mass fraction evolution
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 Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster Hubble diagram
X-ray surface brightness SZE intensity change Eliminate unknown ne to get cluster size L, and hence distance or H0 Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

DA = 1.36  0.15 Gpc H0 = 68  8  18 km s-1 Mpc-1 Worrall & Birkinshaw 2003 XMM gave temperature of 9.13  0.23 keV, central electron density of (8.8  0.5)  103 m -3, abundance 0.22  0.04 solar, beta = 0.70  0.01, core radius 36.6  1.1 arcsec (geometric mean) SZ gives central SZ effect of –1.26  0.07 mK Gas is 0.13  0.02 of total mass within 250 kpc of core. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

poor leverage for other parameters need many clusters at z > 0.5 need reduced random errors ad hoc sample systematic errors cluster evolution should not affect method, can extend to higher z Picture is from Carlstrom, Holder & Reese (2002; ARAA 40, 643). 38 distances for 26 clusters exist: figure shows the high s/n results. Three results: solid line H0 = 60 km s-1 Mpc-1, m = 0.3,  = 0.7, dashed line m = 0.3,  = 0, dash-dot line m = 1.0,  = 0. From Carlstrom, Holder & Reese 2002 Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Levels of study First level: detection of integrated effect Second level: structure of integrated effect Still rudimentary (compare X-ray images) Low dynamic range of data in contrast (20:1 about best) Low dynamic range of data in angular scale (5:1 about best) Astrophysics of cluster structure formation, thermalization of gas, cluster mergers Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster gas structures
Better measured in the X-ray, since higher signal/noise. But in principle the ne dependence of the SZ effect gives higher sensitivity to cluster edges than ne2. Gas structure poorly sampled by current tSZ data: few map points (radiometer arrays), poor angular dynamic range (interferometers). New bolometer data (MUSTANG, APEX-SZ) better. Aim: go beyond global models to astrophysics of gas structures – atmosphere assembly physics, feedback. NFW  Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster gas structures
Effective use of SZ to get gas structures requires high sensitivity (long integrations/low systematic errors) good beamshape knowledge (hard for arrays) excellent angular dynamic range (hard for interferometers) good avoidance of confusion and cluster AGN Variety of cluster substructures (shocks, etc.) will also affect interpretation of large-scale structure. Future of SZ effect may be in finding pressure substructures. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Lensing and SZ effect Weak lensing measures ellipticity field e, and so surface mass density Surface mass density map combined with SZ effect map gives a map of fb  SRJ/, and shows distribution of baryons relative to dark matter in clusters. Integrated over solid angle gives measure of fb. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Lensing and SZ effect 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 XMM gave temperature of 9.13  0.23 keV, central electron density of (8.8  0.5)  103 m -3, abundance 0.22  0.04 solar, beta = 0.70  0.01, core radius 36.6  1.1 arcsec (geometric mean) SZ gives central SZ effect of –1.26  0.07 mK Gas is 0.13  0.02 of total mass within 250 kpc of core. CL with XMM Worrall & Birkinshaw 2003 Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Lensing and the tSZ effect
pixel data from simulations 4.25 clusters identified in simulations × Noise dominated region 4.5 Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Levels of study First level: detection of integrated effect Second level: structure of integrated effect Third level: use of integrated effect to find clusters Focus of most new instruments: SZA, SPT, APEX/LABOCA, AMI, OCRA-F, AMiBA, … Extensive low-z sample from Planck Emphasis on cosmology via cluster counts: redshift distribution sensitive to σ8 (or Λ) Generally rely on multi-band separation of SZ and primary CMB signals Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster surveys: X-ray
XMM-LSS field Contains many cluster candidates at z > 1 Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster counts SZ-selected samples almost mass limited and orientation independent potentially more sensitive than X-ray at high z 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 surveys First large survey results starting to emerge (Bonn meeting, last week) Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster counts Cluster counts and redshift distribution provide strong constraints on 8, m, and cluster heating. dN/dz 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 2001 Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster counts SZ-selected samples limited by changing cluster linear size (and temperature) and coherence at high z since selection is by thermal energy content maximum detectable redshift probably  2 evolution little constrained by SZ data – observations over a wide range of redshift, but insufficient angular dynamic range; need ye distribution at several z need for good follow-up SZ imaging of cluster samples, including multi-band removal of CMB (10 arcsec or better angular resolution; 10 μK or better noise; μJy sensitivities) beware Malmquist bias – flux density surveys Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Levels of study First level: detection of integrated effect Second level: structure of integrated effect Third level: use of integrated effect to find clusters Fourth level: spectral studies Extend cluster surveys to lower temperatures Few attempts at cluster velocities, cluster velocity evolution No serious work on multi-phase plasmas and non-thermal SZ effect Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Cluster radial velocity
kinematic effect z-independent in I() separable from thermal SZ effect by spectrum confusion with primary CMB limits velocity accuracy to about 150 km s-1 velocity substructure in atmospheres will reduce accuracy further statistical measure of velocity distribution of clusters as a function of redshift from cluster samples Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Need good SZ spectrum X-ray temperature Confused by CMB structure Sample  vz2 Few clusters so far, vz  1000 km s A 2163; figure from LaRoque et al Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Extracting the kinematic SZ effect requires spectral separation, so absolute calibration to high precision over range of wavelengths excellent bandpass calibration to fit spectrum well knowledge of cluster thermal structure – also requires precision calculation of spectrum including relativistic and multiple-scattering effects Expect velocity substructure in cluster gas from mergers and infall – might be observable in future If can detect statistically in samples of clusters at different redshifts, can get measure of kinematic evolution of clustering (new datum for cluster formation studies) Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

J at z = 0.548 Particularly interesting in mergers such as this. Clearly disturbed, shock-like structure, filament. Hot! Structure on few arcsec scale, large field map needed. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

SZ effect confusion on CMB
thermal SZ kinematic SZ RS effect Figure from Molnar & Birkinshaw 2000 Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

SZ effect confusion on CMB
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. Need new technology to perform surveys to low-mass, high-z clusters. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

CMB properties Ratio of SZ effects at two ν is a function of TCMB (some dependence on Te and cluster velocity) Use SZ effect spectrum to measure CMB temperature at distant locations and over range of redshifts Test Trad  (1 + z) SZ results plus molecular excitation Battistelli et al. (2002) Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Levels of study First level: detection of integrated effect Second level: structure of integrated effect Third level: use of integrated effect to find clusters Fourth level: spectral studies Fifth level: polarization No useful work to date Access to 3-D velocity field, remote measure of Q Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

CMB properties CMB power spectrum shows low quadrupolar power r Measure quadrupole at other places in Universe SZ effect polarization, important term is conversion of CMB quadrupole to linear polarization Polarization signal small, confused by larger effect of cluster lensing CMB polarization Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

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 Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

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 Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Use Size (mK) Critical issues Cluster formation 0.02 Absolute calibration Transverse velocity 0.01 Confusion; polarization calibration Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Things to shoot for First level: detection of integrated effect. Simple for high-temperature clusters Second level: structure of integrated effects. Depends on noise characteristics, sensitivity, CMB removal Third level: use integrated effect to find clusters. Similar requirements to structure, but on large sky areas Fourth level: spectral studies. Essentially new contribution of current and next generation Velocity information requires significant cluster sample Multi-component study requires high signal/noise Fifth level: polarization. Would be completely new Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

Possible SZ unique studies
Fast hot outflows around ionizing objects at recombination (or later) may show kinematic SZ with little thermal SZ. Information on multiple components in cluster atmospheres via spectral studies. Inversion of spectrum into electron distribution function. Information on developing cluster velocity field. Non-thermal SZ effect in large-scale radio sources to test equipartition (c.f., X-ray inverse-Compton studies). Also issue of non-standard electron populations seen in hot spots and jets. Cambridge; 20 July 2009 Mark Birkinshaw, U. Bristol

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