2. The “QUEST” for CMB Polarization Walter K. Gear Cardiff University

3. Talk Structure CMB ReviewCMB Review Why Polarization ?Why Polarization ? The QUEST ExperimentThe QUEST Experiment (Future Plans)(Future Plans)

4. Curtesy Wayne Hu htp:\\background.uchicago.edu

5. CMB: Cosmic Rosetta Stone... CMB arises from last-scattering surface ~300,000 years after the Big BangCMB arises from last-scattering surface ~300,000 years after the Big Bang This is the earliest direct image of the Universe we can ever obtain (EM anyway…)This is the earliest direct image of the Universe we can ever obtain (EM anyway…) The imprints of structure of the Universe today AND BigBang/inflation should also be imprinted there...The imprints of structure of the Universe today AND BigBang/inflation should also be imprinted there...

6. Constraining Inflation Accurate measurement of the CMB can constrain the nature of the inflationary potential in particular the ratio of scalar to tensor fluctuation amplitude r=T/S and the slope n of the assumed power- law spectrum P(k):

7. Scalars and Tensors Inflation predicts a mixture of scalar (pure density) and Tensor (gravity wave)fluctuations Inflation predicts a mixture of scalar (pure density) and Tensor (gravity wave)fluctuations The precise ratio is a function of the type of field which causes inflation The precise ratio is a function of the type of field which causes inflation Scalar fluctuations couple to matter and provide the “seeds” for structure formation Scalar fluctuations couple to matter and provide the “seeds” for structure formation Tensor perturbation causes a ‘background’ of gravity waves Tensor perturbation causes a ‘background’ of gravity waves

8. CMB: The Golden age….

9. Temperature power spectra

10. CMB: The Golden Age …..

11. Flat, n=1;  b = 0.021,  c = 0.196, H o = 47;  b = 0.022,  c = 0.132, H o = 68,  = 2/3

13. The MAP Temperature results…..

14. The anisotropy measurements have been a triumph, BUT …. “With temperature data alone, r of less than ~0.1 cannot be detected, no matter how accurate the measurement” (Kinney 1999 astroph/9806259 ) “With temperature data alone, r of less than ~0.1 cannot be detected, no matter how accurate the measurement” (Kinney 1999 astroph/9806259 ) With polarization data however we can break this degeneracy (amongst others) With polarization data however we can break this degeneracy (amongst others)

15. The power of polarization… Fundamental prediction of standard theory, if not detected at  then there would be real problemFundamental prediction of standard theory, if not detected at  then there would be real problem The extra information provided by polarization allows much better constraints on some vital cosmological parameters - 4 power spectra rather than 1.The extra information provided by polarization allows much better constraints on some vital cosmological parameters - 4 power spectra rather than 1. Combination of P and  T improves some parameter constraints by factors 2-3 in most models Combination of P and  T improves some parameter constraints by factors 2-3 in most models Break degeneracy between intrinsic fluctuation amplitude and re-ionization Break degeneracy between intrinsic fluctuation amplitude and re-ionization Separate scalar and tensor modes in the initial fluctuation spectra, if B as well as E modes can be detected Separate scalar and tensor modes in the initial fluctuation spectra, if B as well as E modes can be detected

16. Temperature is a scalar but Polarization is a second-rank Tensor It is convenient to write this is as the sum of the gradient and curl of a scalar and vector field E and B [but has nothing to do with E and B EM fields !!]

17. E and B modes The scalar function E represents pure density fluctuationsThe scalar function E represents pure density fluctuations The tensor function B represents metric fluctuations - gravity wavesThe tensor function B represents metric fluctuations - gravity waves

18. Polarisation of the CMB QU + Temperature Generated by Thompson scattering off electrons in quadrupolar motion.Generated by Thompson scattering off electrons in quadrupolar motion. P  Q  U Polarisation Matrix:

19. E/B Decomposition Can decompose Q,U into:Can decompose Q,U into: –E-modes (even-parity): –B-modes (odd-parity): E-modes generated by scalar & tensor perturbations.E-modes generated by scalar & tensor perturbations. B-modes generated by tensors & grav. lensing.B-modes generated by tensors & grav. lensing. B E B E Cold Spot Hot Spot

20. Pure E(left) & B(right)

21. CMB polarisation spectra Have 4 possible spectra:Have 4 possible spectra: TT, TE, EE, BB. by parity.TB = EB = 0 by parity. Gravitational Waves Reionisation Gravitational Lensing Silk Damping Sachs-Wolfe Acoustic Oscillations

22. 19/9/2002: DASI announces E-mode detection !!

23. WMAP Results Temp-Polzn Cross-Power spectra: (l+1)C l TE /2  High low-l modes. Adiabatic acausal perturbations. Line based on T-data only. (no free parameters.)

24. CMB Polzn exists! What now? Detection only so far, need to first map out the E-mode spectrum into the peak region& damping tail & properly measure reionization peak.Detection only so far, need to first map out the E-mode spectrum into the peak region& damping tail & properly measure reionization peak. Measure B-mode contamination from lensing => mass clumping history from LSS to now => dark energy?Measure B-mode contamination from lensing => mass clumping history from LSS to now => dark energy? Eventually measure primordial B-modes=> constrain inflationEventually measure primordial B-modes=> constrain inflation

25. How to measure polarization ? Measuring such tiny signals inevitably involves differencing to minimize systematics and multiple levels of modulationMeasuring such tiny signals inevitably involves differencing to minimize systematics and multiple levels of modulation Broad bandwidths also generally required for sensitivity => BolometersBroad bandwidths also generally required for sensitivity => Bolometers Need careful foreground identification and subtraction => multi-frequencyNeed careful foreground identification and subtraction => multi-frequency

26. Planck Surveyor Planck-HFI will conduct all-sky survey to 5’ in 2007-2009Planck-HFI will conduct all-sky survey to 5’ in 2007-2009

27. Why do it from the ground ? Can in principle obtain much smaller angular scales than from satelliteCan in principle obtain much smaller angular scales than from satellite Can concentrate on smaller pieces of sky than MAP or Planck and go deeper quickerCan concentrate on smaller pieces of sky than MAP or Planck and go deeper quicker Can concentrate on range of multi-poles that offer largest predicted amplitude and best parameter discriminationCan concentrate on range of multi-poles that offer largest predicted amplitude and best parameter discrimination Differencing means both polzns go through same column of atmosphere - not so sensitive to atm noise as  T ground-based experimentsDifferencing means both polzns go through same column of atmosphere - not so sensitive to atm noise as  T ground-based experiments Can upgrade and repair instrument, more flexibility and (a lot!) less costCan upgrade and repair instrument, more flexibility and (a lot!) less cost

28. THE QUEST Project There is a need for a deep (~  K), small area (10s to 100s sq. deg) polzn experiment which will report on a short timescaleThere is a need for a deep (~  K), small area (10s to 100s sq. deg) polzn experiment which will report on a short timescale. The Q and U E xtragalactic S ubmm T elescope project aims to fill this gap.The Q and U E xtragalactic S ubmm T elescope project aims to fill this gap. It is a joint UK/US project capitalising on expertise and heritage of SCUBA, SuZie, BOOMERANG and Herschel/Planck, amongst many.It is a joint UK/US project capitalising on expertise and heritage of SCUBA, SuZie, BOOMERANG and Herschel/Planck, amongst many.

29. QUEST Collaboration: Cardiff: W. Gear, P.Ade, L. Piccirillo- telescope, cryogenics, filters Stanford: Sarah Church - Focal plane & electronics JPL/Caltech: Jamie Bock & Andrew Lange - detectors + K. Ganga (JPL), A. Taylor (Edin) + associates Q and U Extragalactic Submm Telescope

30. Flexibility of QUEST A real experiment has a sensitivity of: (Knox 1995)  T – sensitivity/pixel/Stokes parameter  pix – pixel size Optimum

31. Normally in a ground-based CMB experiment one has to chop to remove atmosphere. However there is always a residual uncancelled emission which often dominates the noise

32. For a polarization experiment however we difference two polarizations which travel through the same column of atmosphere - no need to chop - and also makes dish simpler and cheaper

33. Choice of Filter Bands Motivated by science – avoid and remove foregroundsMotivated by science – avoid and remove foregrounds Only two frequencies simplifies the design of the refracting reimaging opticsOnly two frequencies simplifies the design of the refracting reimaging optics 25.0 Bandwidth (%) 165128147Band 2 1058193Band 1 Upper edge (GHz) Lower edge (GHz) Center (GHz)

34. Predicted sensitivities For 1mm PWV NETs :- 100 GHz~0.3 150 GHz~0.4mK

35. The QUEST Focal Plane Design n Each channel will use a PSB 419143 612100 Beam size (arcmin) Number of Feeds Frequency (GHz)

36. QUEST OPTICAL DESIGN Wide-field (1.5 degrees), good optical quality (strehl >0.9), broadband (90-220 GHz)Wide-field (1.5 degrees), good optical quality (strehl >0.9), broadband (90-220 GHz) On-axis and symmetricOn-axis and symmetric Cold pupil-stop, small in order to fit waveplateCold pupil-stop, small in order to fit waveplate

37. QUEST OPTICAL DESIGN

38. Cold Optics Overview The lenses and waveplate are cooled to 4KThe lenses and waveplate are cooled to 4K All components have a broad-band anti- reflection coatingAll components have a broad-band anti- reflection coating sapphire waveplate is located close to the cold stopsapphire waveplate is located close to the cold stop The cold stop is located at an image of the primary mirrorThe cold stop is located at an image of the primary mirror Lens 1 Lens 2 Sapphire achromatic waveplate

39. QUEST TELESCOPE QUEST telescope is 2.6m Cassegrain with foam-cone supporting secondaryQUEST telescope is 2.6m Cassegrain with foam-cone supporting secondary Designed to rotate around 3 axes - Az, El and also centreline of primary (‘Z’)Designed to rotate around 3 axes - Az, El and also centreline of primary (‘Z’) Will point and track +/- 45 deg from Zenith with 0.3 arcmin rmsWill point and track +/- 45 deg from Zenith with 0.3 arcmin rms Because of novel optical design, cryostat is mounted through centre of primaryBecause of novel optical design, cryostat is mounted through centre of primary

41. QUEST Site and schedule Officially begin operations in Chile spring 2004Officially begin operations in Chile spring 2004 But …….But …….

42. QUEST on DASI We have been approached by and are in detailed discussion with the DASI teamWe have been approached by and are in detailed discussion with the DASI team Which is likely to result to a late switch to the South Pole….Which is likely to result to a late switch to the South Pole….

43. QUEST Science Goals n n To map CMB polarization on angular scales > 3 n n Optimized to map E-modes, and B-modes produced by gravitational lensing and gravity waves Hu et al. 2002 Planned l -space coverage of QUEST the largest scales will be determined by scan strategy and the exact science goals

44. Survey Strategy Two major surveys for separate goalsTwo major surveys for separate goals ~1000 sq. deg survey for detailed E-mode measurement (~6 months)~1000 sq. deg survey for detailed E-mode measurement (~6 months) ~30 sq.deg survey for detailed B-mode measurement (~18 months) to detect lensing signal and possibly primordial gravity waves…..~30 sq.deg survey for detailed B-mode measurement (~18 months) to detect lensing signal and possibly primordial gravity waves…..

45. E-Modes Maximum (S/N) EE ~100.Maximum (S/N) EE ~100. 1000 sq degs, 2000hrs1000 sq degs, 2000hrs. EE BB, GL BB, GW

46. TE-Correlation 1000 sq degs1000 sq degs Cross-correlate QUEST & WMAP. Cross-correlate QUEST & WMAP. TT

47. B-Modes Maximum (S/N) BB > 5, detection of B-modes.Maximum (S/N) BB > 5, detection of B-modes. 2 x 30 sq degs, 2000hrs.2 x 30 sq degs, 2000hrs. EE BB, GL BB, GW

48. Comparing QUEST with other experiments EE BB, GW

49. Cosmological Parameter Forecasts  m h   Matter density  b h   Baryon density h  Hubble parameter  Reionisation optical depth n s  Scalar spectral index  Scalar amplitude (~  8 ) r  Ratio of scalar to tensors Fisher Information Matrix analysis of cosmological parameters.Fisher Information Matrix analysis of cosmological parameters. Use a 7 parameter set:Use a 7 parameter set:

50. Cosmological Parameter Forecasts  b h   h  n s  r  m h   b h   h   n s  2 yr QUEST + 4 yr WMAP 4 yr WMAP

51. Cosmological Parameter Forecasts Factor 3 improvement in r.Factor 3 improvement in r. Factor 2 improvement in n sFactor 2 improvement in n s. 4 yr WMAP 2 yrs QUEST + 4 yrs WMAP

52. Science Summary QUEST will measure EE-Power with s/n=100 over very large l-range – reionisation? Neutrinos? Should detect and measure BB-Power Spectrum. Cosmological Parameters: 2 yr QUEST will improve 4 yr WMAP by factors 2-3. Main improvement on n s & r, so stronger constraints on inflation. Test isocurvature modes from Inflation. Test for non-Gaussianity. Direct measure of P(k) from grav lensing. Due to start early 2005 & run for 2 yrs.

53. Future Plans …. QUEST and other plannned experiments will only measure T/S~0.05-0.1QUEST and other plannned experiments will only measure T/S~0.05-0.1 To go deeper requires more sensitivity and systematic rejectionTo go deeper requires more sensitivity and systematic rejection Lensing contamination probably means a limit >0.001Lensing contamination probably means a limit >0.001 NASA already planning a dedicated B- mode satellite ~2015NASA already planning a dedicated B- mode satellite ~2015

54. Future Plans These ‘4th generation’ experiments will require ~x100 improvement in sensitivity and systematic rejectionThese ‘4th generation’ experiments will require ~x100 improvement in sensitivity and systematic rejection We (Cardiff&Cambridge) planning a UK programme of ground-based and possibly balloon- borne B-mode experimentsWe (Cardiff&Cambridge) planning a UK programme of ground-based and possibly balloon- borne B-mode experiments We believe a combination of the existing bolometer technology with interferometric imaging is the way to achieve this……… but that is another seminar entirely !We believe a combination of the existing bolometer technology with interferometric imaging is the way to achieve this……… but that is another seminar entirely !