Angiola Orlando for the BICEP2 Collabora7on

Transcription

1 Angiola Orlando for the BICEP2 Collabora7on

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3 History of the Universe Universe becomes transparent 3

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6 Next few slides are placeholders for Chao Lin s slides on what is inflation, why do we believe it, GWs as smoking gun, how GW's make the B-mode pattern, it is very faint! (1/20,000,000, i.e. for every 20,000,000 photons oriented like his, on average you may get 20,000,001 oriented the other.)

7 Next few slides are placeholders for Chao Lin s slides on what is inflation, why do we believe it, GWs as smoking gun, how GW's make the B-mode pattern, it is very faint! (1/20,000,000, i.e. for every 20,000,000 photons oriented like his, on average you may get 20,000,001 oriented the other.)

8 The Cosmic Microwave Background (CMB) Planck Collaboration & ESA Planck I 2013 All sky CMB temperature map Angiola Orlando for The Bicep2 Collaboration

9 The Cosmic Microwave Background (CMB) The CMB traces the conditions of the universe at the time when atoms first began to form. Precision measurements of the CMB temperature have provided a wealth of cosmological information consistent with the inflationary paradigm. FFT Angular power spectrum describes correlations in temperature anisotropies across the sky as function of angular scale ~ 1 degree ~ 0.1 degree Planck Collaboration & ESA Angiola Orlando for The Bicep2 Collaboration

10 CMB Polarization From Thomson scattering wherever there is ionized gas and quadrupole anisotropy Quadrupole Anisotropy ' arises at last scattering from local radiation quadrupole ' e Thomson Scattering Linear Polarization Angiola Orlando for The Bicep2 Collaboration Wayne Hu ( A CMB Polarization Primer )

11 Tensor and scalar modes produce local quadrupoles Quadrupoles generated by: o Velocity gradients in the photon-baryon fluid (density waves) SCALAR MODES o Gravitational redshifts associated with gravitational waves TENSOR MODES Quadrupole Anisotropy ' e ' Thomson Scattering Linear Polarization Wayne Hu

12 Patterns of CMB Polarization Polariza7on parallel or perpendicular to wave vector No curl component Density (scalar) fluctua7ons generate only E- mode polariza7on 12

13 Patterns of CMB Polarization Polariza7on oriented at 45 degrees to wave vector Curl component Density fluctua7ons cannot make B- mode panerns 13

14 CMB Polarization The plasma physics of the early universe causes the CMB to become slightly polarized. E-mode Polarization can be described as the sum of E-modes and B-modes. Density fluctuations cannot make B- mode patterns. Only inflationary gravitational waves can induce significant B-mode polarization on degree angular scales. B-mode A measurement of degree-scale B- modes would be direct evidence for the gravitational wave background. Angiola Orlando for The Bicep2 Collaboration

15 CMB Polarization Temperature spectrum In standard ΛCDM only E-modes are present at last scattering E- mode During propagation some of the E- modes are confused into B- modes by lensing Inflationary gravitational waves are unique source of B-modes peaking at l 100 : degree scales Angiola Orlando for The Bicep2 Collaboration

16 The Long Search for B- modes In simple infla7onary gravita7onal wave models the tensor- to- scalar ra:o r lensing is the only parameter to the B- mode spectrum. Un:l March 17 only upper limits ~ 1 degree Best previous limit on r from BICEP1: r < 0.7 (95% CL) Lensing deflects CMB photons, slightly mixing the dominant E- modes into B- modes - - dominant at high mul7poles 16

17 B- modes from the ground Deep, Concentrated coverage Foreground avoidance (limited frequency) Systema7c control with in- situ calibra7on Large detector count, rapid technology cycle Relentless observing & large number of null tests powerful recipe for high- confidence ini7al discovery

18 BICEP2 Strategy: Unique Optics Telescope as compact as possible while still having the angular resolution to observe degree-scale features (target the 2 degree peak of the B- mode) On-axis, refractive optics allow the entire telescope to rotate around boresight for polarization modulation. Liquid helium cools the optical elements to 4.2 K. A 3-stage helium sorption refrigerator further cools the detectors to 0.27 K. 1.2 m Camera tube Optics tube Lens Nylon filter Lens Nb magnetic shield Focal plane assembly Passive thermal filter Flexible heat straps Fridge mounting bracket Refrigerator Camera plate Angiola Orlando for The Bicep2 Collaboration

19 BICEP2 Strategy: Revolutionary detectors JPL : antenna-coupled TES arrays BICEP1 BICEP GHz detectors GHz detectors

20 Superconducting detector arrays Focal plane Planar antenna array Slot antennas Transition edge sensor Polarimeter unit (two orthogonal linear polarizations)

21 Superconduc7ng thermometer Detec:ng CMB Radia:on BICEP2 Detector: Transi:on- Edge Sensor Thermal isola7on Radia7on From Antenna Printed Antenna Gathers CMB Light CMB 0.1 mm Radia7on converted to heat x 32 SQUIDs Amplify and Mul:plex Signals Sensors cooled to 0.27 K to reduce thermal noise SQUIDs developed at NIST

22 BICEP2 Frequency Response The dry South Pole atmosphere provides excellent observing conditions most of the year. The 28% fractional bandwidth fits within an atmospheric transmission window straddled by oxygen and water lines. In this window, the atmosphere is transparent to microwaves. The detector passband is defined by a filter printed directly onto the focal plane wafers. Angiola Orlando for The Bicep2 Collaboration

23 Sensitivity through detector count increase

24 BICEP2 Observational Strategy Example: FDS dust model Target the Southern Hole - a region of the sky exceptionally free of dust and synchrotron foregrounds. Detectors tuned to 150 GHz, near the peak of the CMB s 2.7 K blackbody spectrum. At 150 GHz the combined dust and synchrotron spectrum is predicted to be at a minimum in the Southern Hole. Expected foreground contamination of the B-mode power: r ~0.01. Angiola Orlando for The Bicep2 Collaboration

25 The Bicep2 Collaboration BICEP2 Strategy: the South Pole

26 South Pole CMB telescopes 10m South Pole Telescope BICEP1 BICEP2 DASI QUAD Keck Array NSF s South Pole Station: A popular place with CMB Experimentalists! Super dry atmosphere and 24h coverage of Southern Hole. Also power, LHe, LN 2, 200 GB/day, 3 square meals, bingo night...

27 photo: Keith Vanderlinde"

28 BICEP2 on the Sky Projec7on of the BICEP2 focal plane on the sky The focal plane is 20 degrees across Background is the CMB temperature map as measured with BICEP2

29 South Pole: Relentless Observing

30 Raw Data Perfect Weather Time 50 mins Telescope Movement Sum of detector pairs Difference of detector pairs Cover the whole CMB field in 60 such scans Angiola Orlando for The Bicep2 Collaboration Difference detectors in each pair to remove atmospheric noise before making polarization maps

31 BICEP2 3-year Data Set Live Time on source after cuts Instantaneous Sensitivity Cumulative Map Depth Final map depth: Angiola Orlando for The Bicep2 Collaboration

32 BICEP2 T and Stokes Q/U Maps Angiola Orlando for The Bicep2 Collaboration Signal Maps Difference ( Jackknife ) Maps

33 Total Polarization Scale: B-modes of r=0.1 contribute ~1/10 of the total polarization amplitude at l=100

34 B-mode Contribution Scale: B-modes of r=0.1 contribute ~1/10 of the total polarization amplitude at l=100

35 B-mode Contribution Scale: Zoom in by factor 6 see swirly B-mode

36 Angiola Orlando for The Bicep2 Collaboration BICEP2 E- and B-mode Maps

37 Angiola Orlando for The Bicep2 Collaboration BICEP2 E- and B-mode Maps

38 BICEP2 B-mode Power Spectrum B-mode power spectrum temporal split jackknife lensed-λcdm r=0.2 B-mode power spectrum estimated from Q&U maps Consistent with lensing expectation at higher l. At low l clear detection of B-modes over lensing floor. For the hypothesis that the measured band powers come from lensed-λcdm we find: Angiola Orlando for The Bicep2 Collaboration χ2 PTE significance

39 Polarized Dust Foreground Projections FDS Model The BICEP2 region is chosen to have extremely low foreground emission. Use various models of polarized dust emission to estimate foregrounds. Dashed: Dust auto spectra Solid: BICEP2xDust cross spectra Data driven models (DDM) use Planck dust model (2013) and 47ESLAB (2013) a. All dust auto spectra well below observed signal level. a Session07_Galactic_Science/47ESLAB_April_04_11_25_Bernard.pdf Cross spectra consistent with zero.

40 Cross Spectra between 3 Experiments Form cross spectrum between BICEP2 and BICEP1 combined ( GHz): BICEP2 auto spectrum compatible with B2xB1c cross spectrum ~3σ evidence of excess power in the cross spectrum Additionally form cross spectrum with 2 years of data from Keck Array, the successor to BICEP2 Excess power is also evident in the B2xKeck cross spectrum Cross spectra: Powerful additional evidence against a systematic origin of the apparent signal

41 Constraint on Tensor-to-scalar Ratio r Uncertainties here include sample variance at r=0.2 best fit Substantial excess power in the region where the inflationary gravitational wave signal is expected to peak Find the most likely value of the tensor-to-scalar ratio r Apply direct likelihood method, uses: lensed-λcdm + noise simulations weighted version of the 5 bandpowers B-mode sims scaled to various levels of r (n T =0) Within this simplistic model we find: with uncertainties dominated by sample variance PTE of fit to data: 0.9 model is perfectly acceptable fit to the data r = 0 disfavored at 7.0σ

42 Compatibility with Indirect Limits on r Constraint on r with running allowed: Indirect limit on r from combination of temperature data over a wide range of angular scales: SPT+WMAP+BAO+H 0 Planck+SPT+ACT+WMAP pol : r < 0.11 : r < 0.11 This apparent tension can be relieved with various extensions to lensed ΛCDM. Example: running of the spectral index Planck likelihood chains for lensed ΛCDM + tensors + running Same chains, importance sampled with the BICEP2 r likelihood Other possibilities within ΛCDM?...

43 Compatibility with Indirect Limits on r Using temperature data over a wide range of angular scales limits on r have been set: SPT+WMAP+BAO+H 0 : r < 0.11 Planck+SPT+ACT+WMAP pol : r < 0.11 (95% CL) However, r=0.2 just makes a small change to the temperature spectrum. (In this plot r=0.2 simply added to Planck best fit model with no re-optimization of other parameters) The Bicep2 Collaboration

44 Conclusions BICEP2 and upper limits from other experiments: Most sensitive polarization maps ever made Power spectra perfectly consistent with lensed ΛCDM except: 5.2σ excess in the B-mode spectrum at low multipoles (l~100)! 7σ preference for non-zero r above lensed ΛCDM Extensive studies and jackknife test strongly argue against systematics as the origin Polarbear SPT x-corr Consistent with expectations for primordial gravitational waves from inflation Foregrounds do not appear to be a large fraction of the signal: foreground projections lack of cross correlations CMB-like spectral index shape of the B-mode spectrum Constraint on tensor-to-scalar ratio r in simple inflationary gravitational wave model: