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Nanjing, March 2003 Using the Sunyaev-Zeldovich effect to probe the gas in clusters Mark Birkinshaw University of Bristol.

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Presentation on theme: "Nanjing, March 2003 Using the Sunyaev-Zeldovich effect to probe the gas in clusters Mark Birkinshaw University of Bristol."— Presentation transcript:

1 Nanjing, March 2003 Using the Sunyaev-Zeldovich effect to probe the gas in clusters Mark Birkinshaw University of Bristol

2 Nanjing, March 2003 Mark Birkinshaw, U. Bristol2 Outline 1.The origin of the effect 2.SZ effect observations 3.SZ effect science: clusters 4.SZ effect science: cosmology 5.The future: dedicated SZ instruments 6.Summary

3 Nanjing, March 2003 Mark Birkinshaw, U. Bristol3 1. The origin of the effect Clusters of galaxies contain extensive hot atmospheres T e 6 keV n p 10 3 protons m -3 L 1 Mpc 2 Mpc

4 Nanjing, March 2003 Mark Birkinshaw, U. Bristol4 Inverse-Compton scatterings Cluster atmospheres scatter photons passing through them. Central iC optical depth e n p T L Scatterings changes the average photon frequency by a fraction k B T e /m e c 2

5 Nanjing, March 2003 Mark Birkinshaw, U. Bristol5 Microwave background spectrum I Fractional intensity change I/I = -2 ( / e 10 -4

6 Nanjing, March 2003 Mark Birkinshaw, U. Bristol6 Thermal SZ effect Fractional intensity change in the CMB I/I = -2 ( / e Effect in brightness temperature terms T RJ = -2 T r ( / e -300 K Brightness temperature effect, T RJ, is independent of redshift Flux density effect, S, decreases as D A -2, not D L -2, and depends on redshift

7 Nanjing, March 2003 Mark Birkinshaw, U. Bristol7 Spectrum of thermal effect spectrum related to gradient of CMB spectrum zero at peak of CMB spectrum (about 220 GHz) weak dependence on T e

8 Nanjing, March 2003 Mark Birkinshaw, U. Bristol8 SZ sky predicted using structure formation code (few deg 2, y = 0 – ) CMB primordial fluctuations ignored da Silva et al. Predicted SZ effect sky

9 Nanjing, March 2003 Mark Birkinshaw, U. Bristol9 SZ effect and CMB power spectrum Figure from Molnar & Birkinshaw 2000 thermal SZ kinematic SZ RS effect

10 Nanjing, March 2003 Mark Birkinshaw, U. Bristol10 Attributes of SZ effect T RJ is a redshift-independent function of cluster thermal energy, it is a calorimeter T RJ has a strong association with rich clusters of galaxies, it is a mass finder T RJ contains a weak redshift-independent kinematic effect, it is a radial speedometer T RJ has polarization with potentially more uses, but signal is tiny

11 Nanjing, March 2003 Mark Birkinshaw, U. Bristol11 2. SZ effect observations Interferometers: e.g., Ryle, BIMA, OVRO –structural information –baseline range Single-dish radiometers: e.g., OVRO 40-m, OCRA –speed –systematic errors from spillover Bolometers: e.g., SuZIE, SCUBA, ACBAR –speed –structural and spectral information –weather

12 Nanjing, March 2003 Mark Birkinshaw, U. Bristol12 Ryle telescope first interferometric map Abell 2218 brightness agrees with single-dish data limited angular dynamic range Figure from Jones et al. 1993

13 Nanjing, March 2003 Mark Birkinshaw, U. Bristol13 Interferometers restricted angular dynamic range high signal/noise (long integration possible) clusters easily detectable to z 1 Figure from Carlstrom et al. 1999

14 Nanjing, March 2003 Mark Birkinshaw, U. Bristol14 Interferometers restricted angular dynamic range set by baseline and antenna size good rejection of confusing radio sources Abell 665 model, VLA observation available baselines

15 Nanjing, March 2003 Mark Birkinshaw, U. Bristol15 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) Could be designed with better baseline range

16 Nanjing, March 2003 Mark Birkinshaw, U. Bristol16 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

17 Nanjing, March 2003 Mark Birkinshaw, U. Bristol17 Single-dish radiometers 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 Figure from Birkinshaw 1999

18 Nanjing, March 2003 Mark Birkinshaw, U. Bristol18 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

19 Nanjing, March 2003 Mark Birkinshaw, U. Bristol19 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.

20 Nanjing, March 2003 Mark Birkinshaw, U. Bristol20 SCUBA 850 µm images: SZ effect measured in one; field too small

21 Nanjing, March 2003 Mark Birkinshaw, U. Bristol21 MITO MITO experiment at Testagrigia 4-channel photometer: separate components 17 arcmin FWHM Coma cluster detection Figure from De Petris et al. 2002

22 Nanjing, March 2003 Mark Birkinshaw, U. Bristol22 Viper + ACBAR Since 2001: 16-pixel bolometer (ACBAR); 150, 220, 280 GHz (+350 GHz in 2001) Dry air, 3º chopping tertiary, large ground shield 4 – 5 arcmin FWHM Excellent for SZ work

23 Nanjing, March 2003 Mark Birkinshaw, U. Bristol23 A CBAR cluster observations 2002 cluster observations: three of nine objects detected?

24 Nanjing, March 2003 Mark Birkinshaw, U. Bristol24 SZ effect status About 100 cluster detections –high significance (> 10 ) measurements –multi-telescope confirmations –interferometer maps, structures usually from X-rays Spectral measurements improving but still rudimentary –no kinematic effect detections Preliminary blind and semi-blind surveys

25 Nanjing, March 2003 Mark Birkinshaw, U. Bristol25 3. SZ effect science: clusters 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

26 Nanjing, March 2003 Mark Birkinshaw, U. Bristol26 Integrated SZ effects 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

27 Nanjing, March 2003 Mark Birkinshaw, U. Bristol27 Integrated SZ effects 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

28 Nanjing, March 2003 Mark Birkinshaw, U. Bristol28 SZ effect structures Currently only crudely measured by SZ methods (restricted angular dynamic range) X-ray based structures superior Structure more extended in SZ than X-ray: n e rather than n e 2 dependence. SZ should show more about outer gas envelope, but need better sensitivity

29 Nanjing, March 2003 Mark Birkinshaw, U. Bristol29 SZ effects 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 /

30 Nanjing, March 2003 Mark Birkinshaw, U. Bristol30 Total and gas masses Inside 250 kpc: XMM +SZ M tot = ( ) M Lensing M tot = ( ) M XMM+SZ M gas = ( ) M CL with XMM Worrall & Birkinshaw 2002

31 Nanjing, March 2003 Mark Birkinshaw, U. Bristol31 Cluster radial peculiar 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 Velocity substructure in atmospheres will reduce accuracy further Statistical measure of velocity distribution of clusters as a function of redshift in samples

32 Nanjing, March 2003 Mark Birkinshaw, U. Bristol32 Cluster radial peculiar velocity Need good SZ spectrum X-ray temperature Confused by CMB structure Sample v z 2 Three clusters so far, v z 1000 km s A 2163; figure from LaRoque et al

33 Nanjing, March 2003 Mark Birkinshaw, U. Bristol33 4. SZ effect science: 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

34 Nanjing, March 2003 Mark Birkinshaw, U. Bristol34 Cluster Hubble diagram X-ray surface brightness X n e 2 T e ½ L SZ effect intensity change I n e T e L Eliminate unknown n e L I 2 X 1 T e 3/2 H 0 X I 2 T e 3/2

35 Nanjing, March 2003 Mark Birkinshaw, U. Bristol35 Cluster distances and masses CL D A = Gpc H 0 = km s -1 Mpc -1 Worrall & Birkinshaw 2002

36 Nanjing, March 2003 Mark Birkinshaw, U. Bristol36 Hubble diagram poor leverage for other parameters need many clusters at z > 0.5 need reduced random errors ad hoc sample systematic errors From Carlstrom, Holder & Reese 2002

37 Nanjing, March 2003 Mark Birkinshaw, U. Bristol37 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

38 Nanjing, March 2003 Mark Birkinshaw, U. Bristol38 Blind 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 surveys –XMM-LSS survey region ideal, many deg 2

39 Nanjing, March 2003 Mark Birkinshaw, U. Bristol39 Cluster counts and cosmology Cluster counts and redshift distribution provide strong constraints on 8, m, and cluster heating. z dN/dz m =1.0 m =0.3 Figure from Fan & Chiueh 2000

40 Nanjing, March 2003 Mark Birkinshaw, U. Bristol40 A CBAR blind survey CMB5 field, filtered, pointing source blanked. Features at s/n > 4.

41 Nanjing, March 2003 Mark Birkinshaw, U. Bristol41 Baryon mass fraction 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 fraction Figure from Carlstrom et al b / m

42 Nanjing, March 2003 Mark Birkinshaw, U. Bristol42 Microwave background temperature 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 (1 + z)

43 Nanjing, March 2003 Mark Birkinshaw, U. Bristol43 Microwave background temperature Test T (1 + z) SZ results for two clusters plus results from molecular excitation Battistelli et al. (2002)

44 Nanjing, March 2003 Mark Birkinshaw, U. Bristol44 5. The future: dedicated SZ instruments TodayFuture CBIMITO/MADAMiBAAPEX OVRO 40-mRyleOCRAALMA VSAACBARAMIetc. MAPBOLOCAMPlanck SuZIEetc.SZA

45 Nanjing, March 2003 Mark Birkinshaw, U. Bristol45 Survey speeds OCRA will be fastest survey radiometer AMiBA will be fastest survey interferometer Frequencies complementary

46 Nanjing, March 2003 Mark Birkinshaw, U. Bristol46 New SZ interferometers AMiBA SZA AMI solidnearby high-M cluster dashedhigh-z low-M cluster AMIBA90 GHz SZA30 GHz AMI15 GHz Complementary spectral coverage Short baselines crucial for SZ detection Long baselines for radio sources

47 Nanjing, March 2003 Mark Birkinshaw, U. Bristol47 AMiBA ASIAA/NTU project Operational in 2004, prototype (?) 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

48 Nanjing, March 2003 Mark Birkinshaw, U. Bristol48 XMM-LSS survey SZ follow-up XMM survey of 64 deg 2 to erg cm -2 s -1 (0.5 – 2.0 keV) Expect 300 sources deg -2, 12% clusters 2000 clusters SZ imaging will give Hubble diagram to z = 1 Combining X-ray, SZ, shear mapping at z < 0.5 will give baryon fraction and total masses possible SZ detection of IGM filaments?

49 Nanjing, March 2003 Mark Birkinshaw, U. Bristol49 Cluster finding: X-ray vs SZ AMiBA is better than XMM for clusters at z > 0.7 interferometers provide almost mass limited catalogues may find X-ray dark clusters L X (5 ) z

50 Nanjing, March 2003 Mark Birkinshaw, U. Bristol50 OCRA Torun Observatory, Jodrell Bank, Bristol, Bologna OCRA-p

51 Nanjing, March 2003 Mark Birkinshaw, U. Bristol51 OCRA 30 GHz T sys = 40 K 1 arcmin FWHM beam 5 mJy sensitivity in 10 sec now on telescope OCRA-F in progress

52 Nanjing, March 2003 Mark Birkinshaw, U. Bristol52 APEX MPI project at Chajnantor 300-element bolometer array at 870 m ideal for SZ (117-element prototype shown)

53 Nanjing, March 2003 Mark Birkinshaw, U. Bristol53 6. Summary (1) SZ effect is a major cluster and cosmological probe SZ maps dominated by massive objects at z 0.5, filaments and groups tend to average out SZ effect easily detectable to z > 1 SZ effects appear on lumpy background, adds noise

54 Nanjing, March 2003 Mark Birkinshaw, U. Bristol54 Summary (2) Individual cluster SZ effects give –total thermal energy contents –total electron contents –structural information (especially on large scales) –cluster masses –microwave background temperature at distant points

55 Nanjing, March 2003 Mark Birkinshaw, U. Bristol55 Summary (3) 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 –redshift-dependence of microwave background temperature

56 Nanjing, March 2003 Mark Birkinshaw, U. Bristol56 Summary (4) Improved SZ data could give –radio source energetics (non-thermal SZ effect) –radial velocities of clusters (kinematic effect) –transverse velocities of clusters (polarization effect) –detections of gas in in-falling filaments Many new SZ facilities will come on-line in the next 5 – 10 years

57 Nanjing, March 2003 Mark Birkinshaw, U. Bristol57 Attributes of SZ effect T RJ is a redshift-independent function of cluster thermal energy, it is a calorimeter T RJ has a strong association with rich clusters of galaxies, it is a mass finder T RJ contains a weak redshift-independent kinematic effect, it is a radial speedometer T RJ has polarization with potentially more uses, but signal is tiny


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