SZ review

The microwave background radiation and the Sunyaev-

Zel’dovich effect

Mark Birkinshaw

31-October-2002 Mark Birkinshaw, U. Bristol 2

SZ review

Outline

1. The microwave background

2. The origin of the SZ effect

3. SZ observations today

4. Cluster structures and SZ effects

5. Cosmology and SZ effects

6. AMiBA and OCRA

7. Summary

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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

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SZ review

COBE/FIRAS spectrum

FIRAS results: T = 2.728 ± 0.002 K, |y| < 15 10-6, || < 9 10-5 (Fixsen et al. 1996)

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COBE/FIRAS+DMR dipole

FIRAS and DMR measured the dipole:amplitude = 3.372 ± 0.007 mKdirection (l,b) = (264.14° ± 0.15°, 48.26° ± 0.15°)

(FIRAS values, consistent with DMR, but more precise)

Can ignore deviation from monopole temperature.

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BOOMERanG power spectrumPredicted power spectra (MAP errors)

Hu & White (1997)

Temperature power spectrum

BOOMERanGNetterfield et al. (2002)

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Power spectrum interpretation

• Peak locations show Universe is flatk = –0.02 ± 0.06

• Fluctuations close to Harrison-Zel’dovich–ns = 0.96 ± 0.10

• Peak heights give matter contentsb = (0.022 ± 0.004) h2

CDM = (0.13 ± 0.05) h2

• Cosmological concordance still goodNetterfield et al. (2002)

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Polarization

E-mode polarization detection

DASI

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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

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Inverse-Compton scatterings

• Cluster atmospheres scatter photons passing through them. Central iC optical depth

enpT L

• Each scattering changes the photon frequency by a fraction

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Single-scattering frequency shift

5 keV 15 keV

s = log()

P1(s)

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Thermal SZ effect• The fractional intensity change in the background

radiation

I/I = -2 (/ e 10-4

• Effect in brightness temperature terms is

TRJ = -2 Tr (/ e -300 K

• Brightness temperature effect, TRJ, is

independent of redshift

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Microwave background spectrum

I

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Spectrum of thermal effect

• effect caused by small frequency shifts, so spectrum related to gradient of CMB spectrum

• zero at peak of CMB spectrum

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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 keV15 keV

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Spectrum of kinematic effect

• effect caused by reference frame change, related to CMB spectrum

• maximum at peak of CMB spectrum

• negative of CMB spectrum

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Attributes of SZ effect

TRJ is a redshift-independent function of cluster properties only. If the gas temperature is known, it is a leptometer

TRJ contains a weak redshift-independent kinematic effect, it is a radial speedometer

TRJ has a strong association with rich clusters of galaxies, it is a mass finder

TRJ has polarization with potentially more uses, but signal is tiny

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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

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Interferometers

• restricted angular dynamic range set by baseline and antenna size

• good rejection of confusing radio sources

Abell 665 model, VLA observation

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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)

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Ryle telescope

• first interferometric map• Abell 2218• brightness agrees with

single-dish data• limited angular dynamic

range

Figure from Jones et al. 1993

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BIMA/OVRO

• limited angular dynamic range

• high signal/noise (with enough tint)

• clusters easily detectable to z 1

Figure from Carlstrom et al. 1999

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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

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OVRO 40-m

• Crude mapping possible• Difficulties with

variable sources• Relatively fast for

detections of SZ effects

Figure from Birkinshaw 1999

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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

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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.

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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.

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SCUBA

850 µm images: SZ effect measured in one; field too small

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MITO

• MITO experiment at Testagrigia

• 4-channel photometer: separate components

• 17 arcmin FWHM• Coma cluster detection

Figure from De Petris et al. 2002

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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.

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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

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Integrated SZ effects• Total SZ flux density

thermaleeRJ UdzTndS Thermal energy content immediately measured in redshift-independent wayVirial theorem then suggests SZ flux density is direct measure of gravitational potential energy

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Integrated SZ effects• Total SZ flux density

eeeeRJ TNdzTndS 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

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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

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Cluster velocitiesNeed• 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.

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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 ne rather than ne

2 dependence, so good SZ structure should extend out further and show more about halo

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Cluster distances and massesDA = 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+SZCL 0016+16 with XMM; Worrall & Birkinshaw 2002

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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

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Cluster Hubble diagram

X-ray surface brightness

X ne2 Te

½ L SZ effect intensity change

I ne Te L

Eliminate unknown ne

L I2 X1 Te

3/2

H0 X I2 Te

3/2

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Hubble diagram

• poor leverage for other parameters

• need many clusters at z > 0.5

• need reduced random errors

• ad hoc sample • systematic errors

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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

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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

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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

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Cluster counts and cosmologyCluster counts and redshift distribution provide strong constraints on 8, m, and cluster heating.

z

dN/dzm=1.0

m=0.3

m=0.3

Figure from Fan & Chiueh 2000

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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

Figure from Carlstrom et al. 1999.

b/m

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Cluster velocities

Confused by CMB structure, cluster velocity errors of 150 km s-1 at best

(currently worse)

Sample could give z

2(z): dynamics A 2163; figure from LaRoque et al. 2002.

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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)

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Microwave background temperature• Test T (1 + z)

• SZ results for two clusters plus results from molecular excitation

Battistelli et al. (2002)

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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

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New SZ facilities• AMiBA• OCRA (-p, -F, -)• AMI• MAP• Planck• SuZIE-n• BOLOCAM• CARMA• ALMA

• SZA• ACBAR• MITO/MAD• APEX

etc., etc., etc.

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Survey speeds

• OCRA will be fastest survey radiometer

• AMiBA will be fastest survey interferometer

• Frequencies complementary

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AMiBA

• ASIAA/NTU-led project• Operational in 2004, prototype

2002• 19 dishes, 1.2/0.3 m diameters,

1.2 – 6 m baselines = 95 GHz, = 20 GHz• Dual polarization• 1.3 mJy/beam in 1 hr

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Visibility curves• AMIBA 90 GHz• SZA 30 GHz• AMI 15 GHz

Complementary frequencies

Solid: nearby, high-MDashed: distant, low-M

AMiBASZAAMI

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AMiBA confusion• Discrete radio sources

– scaled from 8.4 GHz and 30 GHz counts – expect 1 source >1 mJy per 3 fields: not a problem

• CMB primary anisotropy– most can be filtered out in mosaic mode , < 0.3 mJy

• Faint SZ clusters– cluster counts expect ~ 1 source >1 mJy per field– cluster counts don’t tell the full story since clusters are

clustered. Simulations suggest < 0.3 mJy.

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AMiBA imaging

Simulated AMiBA field from deep survey: two SZ effects detected

Based on da Silva et al. simulations

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AMiBA survey sensitivity

• 5 mass limits in survey modes

• Shallow: 175 deg2 in 6 mon, 100 clusters

• Medium: 70 deg2 in 1 year, 350 clusters

• Deep: 3 deg2 in 6 mon, 100 clusters

shallow

medium

deepM = 214 M

z = 1

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OCRA

Torun Observatory, Jodrell Bank, Bristol, …

OCRA-p

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OCRA

• 30 GHz

• Tsys = 40 K

• 1 arcmin FWHM beam

• 5 mJy sensitivity in 10 sec

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XMM + AMiBA survey aims

• Map large-scale structure of Universe to z = 1 using cluster and quasar populations.

• Cluster formation and evolution will be traced.• Cluster Hubble diagram:

– Compare H0 with value from local Universe standard candles

– Compare with CMB results to check SN Ia results on

• Use cluster z distrubution to get and m

• Cluster physics and baryon fraction at z = 0 – 1

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Cluster finding: XMM and AMiBA

• AMiBA is better than XMM for finding clusters at z > 0.7

• AMiBA surveys will provide an almost mass limited catalogue

LX(5)

z

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7. Summary (1)

• SZ effects are now easily measurable to z = 1

• Individual cluster SZ effects give– total thermal energy contents– total electron contents– structural information (especially on large scales)– peculiar radial velocities– cluster masses

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7. Summary (2)

• Sample studies give– Hubble diagram and cosmological parameters– cluster number counts and cosmological parameters– baryon mass fraction– evolution of cluster atmospheres– evolution of radial velocities– microwave background temperature in distant

Universe

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7. Summary (3)

• Improved SZ data may give– radio source energetics (non-thermal SZ effect)– transverse velocities of clusters (polarization effect)– detections of gas in in-falling filaments