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SZ effect and ALMA The Sunyaev-Zel’dovich effect: background and issues Mark Birkinshaw University of Bristol.

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Presentation on theme: "SZ effect and ALMA The Sunyaev-Zel’dovich effect: background and issues Mark Birkinshaw University of Bristol."— Presentation transcript:

1 SZ effect and ALMA The Sunyaev-Zel’dovich effect: background and issues Mark Birkinshaw University of Bristol

2 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol2 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, y e, the dimensionless electron temperature weighted by the scattering optical depth

3 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol3 1. Simple observables: shape For a simple isothermal  model Typical central value y e0  SZE has larger angular size than X-ray image and weaker dependence on 

4 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol4 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 /k B T CMB = ( /GHz)  I 0 is the specific intensity scale from the thermal SZE

5 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol5 1. Simple observables: spectrum spectrum related to gradient of CMB spectrum zero near peak of CMB spectrum (about 220 GHz)

6 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol6 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   e v z, giving kinematic SZE Same as spectrum of primordial CMB fluctuations: T CMB change.

7 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol7 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

8 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol8 2. Simple observations Simplest: single-dish radiometers/radiometer arrays. Secondary focus: single on-axis feed symmetrical dual feeds array of feeds (large focal plane) Prime focus: single on-axis feed symmetrical dual feeds

9 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol9 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  T A doesn’t reduce with time as  -1/2 after some limiting time, because gain and T sys are unsteady.

10 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol10 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

11 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol11 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

12 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol12 2. Simple observations: interferometers OVRO array in compact configuration (old site).

13 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol13 2. Simple observations: interferometer sensitivity Sensitivity of interferometer N corr = number of antenna-antenna correlations used in making synthesized beam (solid angle  synth ).  source = solid angle of source.

14 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol14 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) Abell 665 model, VLA observation available baselines

15 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol15 2. Simple observations: interferometer maps First interferometric detection of SZE: Ryle telescope, Abell 2218 Jones et al. (1993)

16 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol16 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

17 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol17 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/ )

18 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol18 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.

19 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol19 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

20 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol20 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

21 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol21 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

22 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol22 3. Simple science results: integrated SZE Total SZ flux density If have X-ray temperature, then SZ flux density measures electron count, N e (and hence baryon count) Combine with X-ray derived mass to get f b

23 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol23 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

24 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol24 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 f b  S RJ / 

25 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol25 3. Simple science results: total, gas masses Inside 250 kpc: XMM +SZ M tot = (2.0  0.1)  M  Lensing M tot = (2.7  0.9)  M  XMM+SZ M gas = (2.6  0.2)  M  CL with XMM Worrall & Birkinshaw 2003

26 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol26 3. Simple science results: v z Kinematic effect separable from thermal SZE by different spectrum Confusion with primary CMB fluctuations limits v z 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

27 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol27 3. Simple science results: v z Need good SZ spectrum X-ray temperature Confused by CMB structure Sample   v z 2  Errors  1000 km s  so far A 2163; figure from LaRoque et al

28 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol28 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

29 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol29 3. Simple science results: cluster Hubble diagram X-ray surface brightness SZE intensity change Eliminate unknown n e to get cluster size L, and hence distance or H 0

30 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol30 3. Simple science results: cluster distances CL D A = 1.36  0.15 Gpc H 0 = 68  8  18 km s -1 Mpc -1 Worrall & Birkinshaw 2003

31 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol31 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

32 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol32 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

33 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol33 SZ sky predicted using structure formation code (few deg 2, y = 0 – ) Primordial fluctuations ignored Cluster counts strong function of cosmological parameters and cluster formation physics. 3. Simple science results: SZE sky

34 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol34 See talks of Stefano BorganiScott Kay Antonio da SilvaLauro Moscardini Jim BartlettJoseph Silk 3. Simple science results: SZE sky

35 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol35 3. Simple science results: f B S RJ  N e T e Total SZ flux  total electron count  total baryon content. Compare with total mass (from X-ray or gravitational lensing)  baryon mass fraction Figure from Carlstrom et al b/mb/m

36 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol36 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

37 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol37 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).

38 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol38 4. More complicated observables: detailed structures J z = Clearly disturbed, shock-like substructure, filament What will SZ image look like?

39 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol39 4. More complicated observables: detailed structures See talks by Monique ArnaudDoris Neumann Steen HansenTetsu Kitayama Christoph PfrommerAndrea Lapi

40 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol40 4. More complicated observables: detailed spectra Ratio of SZ effects at two different frequencies is a function of CMB temperature (with slight dependence on T e and cluster velocity) So can use SZ effect spectrum to measure CMB temperature at distant locations and over range of redshifts Test T CMB  (1 + z) Battistelli et al. (2002)

41 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol41 for low-T e gas effect is independent of T e T e > 5 keV, spectrum is noticeable function of T e non-thermal effect (high energies) gives distortion multiple scatterings give another distortion 5 keV 15 keV 4. More complicated observables: detailed spectra

42 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol42 4. More complicated observables: detailed spectra See talks by Francesco MelchiorriBjörn Schaeffer Diego HerranzSergio Colafrancesco Jens Chluba

43 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol43 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

44 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol44 4. More complicated observables: polarization See talks by Doris NeumannAsantha Cooray Jens Chluba

45 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol45 5. Requirements on observations UseSize (mK)Critical issues Energetics0.50 Absolute calibration Baryon count0.50 Absolute calibration; isothermal/spherical cluster; gross model Gas structure0.50 Beamshape; confusion Mass distribution0.50 Absolute calibration; isothermal/spherical cluster Hubble diagram0.50 Absolute calibration; gross model; clumping; axial ratio selection bias

46 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol46 5. Requirements on observations UseSize (mK)Critical issues Blind surveys0.10 Gross model; confusion Baryon fraction evolution 0.10 Absolute calibration; isothermal/spherical cluster; gross model CMB temperature 0.10 Absolute calibration; substructure Radial velocity0.05 Absolute calibration; gross model; bandpass calibration; velocity substructure

47 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol47 5. Requirements on observations UseSize (mK)Critical issues Cluster formation0.02 Absolute calibration Transverse velocity 0.01 Confusion; polarization calibration

48 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol48 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

49 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol49 6. Status at the time of ALMA: See talks by Rüdiger KneisslGuo-Chin Liu Katy LancasterPierre Cox Frank BertoldiJohn Carlstrom Björn Schaefer … and other SZ instrumentation projects

50 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol50 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

51 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol51 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

52 SZ effect and ALMA 7 April 2005Mark Birkinshaw, U. Bristol52 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.


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