The Sunyaev-Zel

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The Sunyaev-Zeldovich effectbackground and
issues

• Mark Birkinshaw
• University of Bristol

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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

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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 ?

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1. Simple observables spectrum

• For clusters which arent 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
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1. Simple observables spectrum

• spectrum related to gradient of CMB spectrum
• zero near peak of CMB spectrum (about 220 GHz)

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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.
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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

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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.

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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 gt 1), but ?TA doesnt reduce with time as
?-1/2 after some limiting time, because gain and
Tsys are unsteady.
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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

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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

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2. Simple observations interferometers

• OVRO array in compact configuration (old site).

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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.
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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
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2. Simple observations interferometer maps

• First interferometric detection of SZE Ryle
  telescope, Abell 2218
• Jones et al. (1993)

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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

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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)

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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.

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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

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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

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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
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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
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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

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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/?
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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?
• XMMSZ
• Mgas (2.6 ? 0.2) ? 1013 M?

CL 001616 with XMM Worrall Birkinshaw 2003
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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

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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.
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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

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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

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3. Simple science results cluster distances

• CL 001616
• DA 1.36 ? 0.15 Gpc
• H0 68 ? 8 ? 18 km s-1 Mpc-1
• Worrall Birkinshaw 2003

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3. Simple science results cluster Hubble diagram

• poor leverage for other parameters
• need many clusters at z gt 0.5
• need reduced random errors
• ad hoc sample
• systematic errors

Carlstrom, Holder Reese 2002
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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

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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.
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3. Simple science results SZE sky
See talks of Stefano Borgani Scott
Kay Antonio da Silva Lauro Moscardini Jim
Bartlett Joseph Silk
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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.
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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

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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).

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4. More complicated observables detailed
structures

• J0717.53745
• z 0.548
• Clearly disturbed, shock-like substructure,
  filament
• What will SZ image look like?

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4. More complicated observables detailed
structures

• See talks by
• Monique Arnaud Doris Neumann
• Steen Hansen Tetsu Kitayama
• Christoph Pfrommer Andrea Lapi

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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)

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4. More complicated observables detailed spectra

• for low-Te gas effect is independent of Te
• Te gt 5 keV, spectrum is noticeable function of Te
• non-thermal effect (high energies) gives
  distortion
• multiple scatterings give another distortion

5 keV
15 keV
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4. More complicated observables detailed spectra

• See talks by
• Francesco Melchiorri Björn Schaeffer
• Diego Herranz Sergio Colafrancesco
• Jens Chluba

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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

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4. More complicated observables polarization

• See talks by
• Doris Neumann Asantha Cooray
• Jens Chluba

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5. Requirements on observations
Use Size (mK) Critical issues
Energetics 0.50 Absolute calibration
Baryon count 0.50 Absolute calibration isothermal/spherical cluster gross model
Gas structure 0.50 Beamshape confusion
Mass distribution 0.50 Absolute calibration isothermal/spherical cluster
Hubble diagram 0.50 Absolute calibration gross model clumping axial ratio selection bias
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5. Requirements on observations
Use Size (mK) Critical issues
Blind surveys 0.10 Gross model confusion
Baryon fraction evolution 0.10 Absolute calibration isothermal/spherical cluster gross model
CMB temperature 0.10 Absolute calibration substructure
Radial velocity 0.05 Absolute calibration gross model bandpass calibration velocity substructure
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5. Requirements on observations
Use Size (mK) Critical issues
Cluster formation 0.02 Absolute calibration
Transverse velocity 0.01 Confusion polarization calibration
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6. Status at the time of ALMA 2005

• Current status
• About 100 cluster detections
• high significance (gt 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

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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

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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 gt 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

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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

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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.