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Seeing the beginning: the Cosmic Microwave Background and what it can tell us about our Universe

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ECL 2018 Autumn Workshop
Presentation by Prof. Blake D. Sherwin
University of Cambridge, UK

Published in: Science
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Seeing the beginning: the Cosmic Microwave Background and what it can tell us about our Universe

  1. 1. Cosmic Microwave Background Lensing: ! Fundamental Physics from Maps of the Invisible! Blake D. Sherwin ! Department of Applied Mathematics and Theoretical Physics / Kavli Institute for Cosmology! University of Cambridge!
  2. 2. But Galaxies Only Trace ! Even More Underlying Dark Matter! 2! Galaxies! Dark Matter! <20% of the mass! Galaxies Trace ! Large Amounts of Underlying Dark Matter! Galaxies, Gas: <20% of the mass!
  3. 3. 3! Dark Matter: >80% of the mass – invisible!! Galaxies Trace ! Large Amounts of Underlying Dark Matter! Image: Virgo Consortium!
  4. 4. Dark Matter! •  > 80 percent of matter is invisible dark matter, distributed in large structures across the universe. ! Image Credit:! Millenium Simulation (Springel et al 2005) ! 4!
  5. 5. Large Scale Dark Matter Structure! •  Want to probe distribution in detail, as contains much information on open questions in cosmology and physics –! ! ! •  Dark matter / mass distribution is what theory robustly predicts.!
  6. 6. Time! Many Open Questions in Cosmology •  We have a very successful theory – the standard (LCDM) cosmological model with 6 free parameters, tested to sub- percent precision.! ! dark matter structure forms through gravitational collapse! dark energy starts accelerating universe apart ! inflation: fast expansion in early universe!
  7. 7. Time! Many Open Questions in Cosmology •  We have a very successful theory – the standard (LCDM) cosmological model with 6 free parameters, tested to sub- percent precision. But: many parts not understood!! ! dark matter structure forms through gravitational collapse! dark energy starts accelerating universe apart ! inflation: fast expansion in early universe!
  8. 8. Large Scale Dark Matter Structure! •  Want to probe distribution in detail, as contains much information on open questions in cosmology and physics:! What is the physics of inflation and the early universe?!
  9. 9. Large Scale Dark Matter Structure! •  Want to probe distribution in detail, as contains much information on open questions in cosmology and physics:! What is dark energy?! ! What is the physics of inflation and the early universe?!
  10. 10. Large Scale Dark Matter Structure! •  Want to probe distribution in detail, as contains much information on open questions in cosmology and physics:! What is dark energy?! ! What are the properties / masses of neutrinos?! What is the physics of inflation and the early universe?!
  11. 11. Large Scale Dark Matter Structure! •  Want to probe distribution in detail, as contains much information on open questions in cosmology and physics:! What is dark energy?! ! What are the properties / masses of neutrinos?! Is standard cosmology correct?! What is the physics of inflation and the early universe?!
  12. 12. Outline! •  Introduction to CMB lensing: mapping cosmic dark matter! •  Lensing as a powerful signal for measuring neutrino masses (+…)! •  Lensing as noise for studying inflation and the early universe! 12!
  13. 13. Observing Dark Matter: Gravitational Lensing! 13! •  Gravity from all matter, including dark matter, deflects radiation that passes by! real! apparent! observer! dark matter! or mass!
  14. 14. Light Source for Studying Lensing: ! Cosmic Microwave Background (CMB) time (+ distance light travels!)! early universe is dense and hot plasma! History of the universe!
  15. 15. time (+ distance light travels!)! early universe is dense and hot plasma! afterglow radiation still visible today:! ! Cosmic! Microwave! Background! Light Source for Studying Lensing: ! Cosmic Microwave Background (CMB) History of the universe!
  16. 16. ! CMB temperature fluctuations (picture of the primordial plasma from the Planck Satellite)! “Light” Source for Lensing: ! The Cosmic Microwave Background (CMB) Radiation! hot/bright! only 1 part in 104! ! cold/dim!
  17. 17. we  are  here     ! !    d     (=projected   matter   density)   Primordial CMB (most distant and oldest source of radiation)! The observable universe:! CMB: A Distant Backlight ! On the Matter Distribution ! dark  ma*er  
  18. 18. CMB Gravitational Lensing! •  Distribution of dark matter deflects CMB light that passes through! 18!
  19. 19. “Light” Source for Lensing: ! The Cosmic Microwave Background (CMB)! •  CMB: leftover radiation from the hot primordial plasma – most distant observable source of light! •  Distribution of dark matter deflects light that passes through! 19!
  20. 20. Unlensed CMB! 10°   CMB Temp.! 20!
  21. 21. Lensed CMB! 10°   CMB Temp.! 21!
  22. 22. 22! ! •  Original, un-lensed, CMB fluctuations. Very well understood statistical properties, e.g., isotropy.! CMB Lensing: An Approximate Picture!
  23. 23. 23! •  Clump of dark matter in front…! CMB Lensing: An Approximate Picture!
  24. 24. 24! ! •  Dark matter causes lensing magnification feature in the CMB! CMB Lensing: An Approximate Picture!
  25. 25. 25! ! •  Dark matter causes lensing magnification feature in the CMB! CMB Lensing: An Approximate Picture! d! d! d! described by lensing deflection field: d! ! (very small: here exaggerated by x ~100, actually a few arcmins)!
  26. 26. CMB Lensing Measurement: ! An Approximate Picture! d: lensing deflection field! CMB!CMB! Temp.! Local CMB power spectrum!
  27. 27. CMB Lensing Measurement: ! An Approximate Picture! d: lensing deflection field! CMB! Temp.! Infer magnification and lensing from “stretching” of the local CMB power spectrum! shift to larger angular scales!
  28. 28. Lensing Reconstruction Details! •  Lensing changes known isotropic and Gaussian statistics: introduces non-Gaussian correlations! ! ! •  So: measure lensing by looking for these non-Gaussian correlations in the CMB two-point function! [Zaldarriaga, Seljak 1997, Hu, Okamoto 2002]! 28! hT(l)T⇤ (l L)i ⇠ d(L) ˆd(L) ⇠ Z d2 l T(l)T⇤ (l L) T: temperature (Fourier mode)! l: wavenumber!
  29. 29. CMB Polarization Lensing Measurement ! ! Characteristic polarization! indicates overdensity! CMB Polarization map! NO background fluctuations – all signals from lensing! No confusion, better measurement in polarization!! better lensing map!
  30. 30. What Does Lensing Tell Us?! •  Lensing probes the projected total mass density in each direction (of which most is dark matter), all the way out! ! ! ! ! ! : fractional mass overdensity! = (⇥ ¯⇥)/¯⇥ 30! lensing deflection! d(ˆn) = Z rCMB 0 drW(r) (ˆn, r) radial! distance! geometric projection kernel, peak at z~2!
  31. 31. •  Lensing probes the projected total mass density in each direction (of which most is dark matter), all the way out! •  (I think) this is remarkable!! ! ! ! ! : fractional mass overdensity! = (⇥ ¯⇥)/¯⇥ geometric projection kernel, peak at z~2! 31! lensing deflection! d(ˆn) = Z rCMB 0 drW(r) (ˆn, r) What Does Lensing Tell Us?! radial! distance!
  32. 32. ! While Galaxy Surveys Are Extremely Powerful, ! Much of the Dark Universe Remains Unexplored! Primordial CMB (most distant source of radiation)! galaxy ! survey (z<1)! The observable universe:!
  33. 33. ! ! Lensing Probes all the Mass ! Projected Back to the CMB Emission! " "d ! =projected! Matter! density! ! ! ! from z~0.5-5! Primordial CMB (most distant source of radiation)! The observable universe:!
  34. 34. !Illustration: future ! full sky lensing map of mass! CMB Lensing Maps Can Gravitationally Probe all the (Projected) Mass in the Observable Universe! Lensing maps of mass: a powerful new probe of cosmology and physics!
  35. 35. Outline! •  Introduction to CMB lensing: mapping cosmic dark matter! •  Lensing as a powerful signal for measuring neutrino masses (+…)! •  Lensing as noise for studying inflation and the early universe! 35!
  36. 36. Physics Lensing Can Tell Us:! Neutrinos!! 36! •  Neutrinos: 3/12 elementary particles. Have mass – associated physics not well understood! •  we don’t know:! –  absolute mass = new scale! ! ! ! !
  37. 37. Motivation: Measuring Neutrino Mass! 37! normal! ordering! inverted ordering! mass! •  Neutrinos have mass – associated physics not well understood! •  we don’t know:! –  absolute mass = new scale! –  order of neutrino masses (2 light, 1 heavy? 2 heavy 1 light?)! –  their own antiparticle?! –  what gives neutrinos mass? +…! •  Cosmology: measurement of mass sum " can give insights! ! ! X m⌫
  38. 38. Physics Lensing Can Tell Us:! Neutrinos!! 38! normal! ordering! inverted ordering! mass! X m⌫ •  If we measure mass sum, can get insight to some of the questions (scale, mass ordering, type)! ! ! ! •  Part of a big program to understand this new physics!! N.B. +look for extra neutrinos!! ! X m⌫ Target: mass at least >60meV !
  39. 39. •  Cosmic neutrino background affects how dark matter structure grows: νs fast so don’t clump (effect size determined by mass)! Neutrinos in Cosmology! Background of fast-moving neutrinos! Cosmic distribution of dark matter! [Yu++2016]!
  40. 40. •  The more massive neutrinos are, the more small scale dark matter structure is suppressed. ! ! ! ! ! ! •  Suppression also visible in lensing map – want to measure (and compare with primordial CMB amplitude)!!!! ! 40! Large-scale! mass distribution:   Neutrinos Affect How Cosmic Structure Grows (via gravitational collapse)! Image:! Viel++! 2013! Neutrino Mass Really Large ! (qualitative)! Neutrino Mass Negligible!
  41. 41. 41! Atacama Cosmology Telescope (ACT)! •  Arcminute resolution CMB telescope high in the Chilean Atacama desert, with arrays of sensitive (TES bolometer) detectors!
  42. 42.                               ACT CMB Temperature Map! ! ! ! ! ! ! CMB Lensing Reconstruction Pipeline for ACT Data! Statistical pipeline for CMB lensing measurement! ! Challenges: ! "- Noise bias measurement! "- Masks and missing data " " "-Bright radio galaxies! "- Astrophysical signal from clusters"-Infrared galaxy emission, …   [Sherwin & Das 2010]!
  43. 43.                               ACT CMB Lensing Dark Matter Map (12 degrees across)! First CMB-only Lensing Measurement: ! Mapping Dark Matter! brightness = density! [Das, Sherwin++ 2011! Sherwin, Dunkley, Das++2011]!
  44. 44.                               Overdensity!Matter underdensity! [Das, Sherwin++ 2011! Sherwin, Dunkley, Das++2011]! brightness = density!
  45. 45.                               Y axis: “How much! lensing ….”! ! ! " " " " "X axis: “for a lens of this angular scale?”! Describe maps statistically with lensing power spectrum.! ACT CMB Lensing Dark Matter Map! brightness = density! Key Observable: CMB Lensing Power Spectrum ! Cdd
  46. 46. CMB lensing map d (e.g., ACT)!strength of lensing! angular wavenumber! Key Observable: CMB Lensing Power Spectrum ! Cdd neutrino mass! (>blurring)! Y axis: “How much! lensing2 ….”! ! ! " " " " " " " X axis: “for a lens of this angular scale?! Cdd L ⇠ hd2 i ⇠ hTTTTi NG! NG! Measurement: non-Gaussianity in four- point function  
  47. 47. 2011 (+2013), ACT! ACT(Pol)   •  Used to confirm: evidence for Dark Energy from CMB data alone! •  2015: POLARBEAR, first detection of lens power in polarization! [Das, Sherwin++ 2011! Sherwin, Dunkley, Das++2011! see also van Engelen++2013]! Detection of the CMB Lensing Power Spectrum! [Physical Review: listed as one of ≈30 landmark papers published in GR in last 100yrs]!
  48. 48. 2011 (+2013), ACT! ACT(Pol)   •  Used to confirm: evidence for Dark Energy from CMB data alone! •  2015: POLARBEAR, first detection of lens power in polarization! [Das, Sherwin++ 2011! Sherwin, Dunkley, Das++2011! see also van Engelen++2013]! Detection of the CMB Lensing Power Spectrum! [Physical Review: listed as one of ≈30 landmark papers published in GR in last 100yrs]!
  49. 49. 49! Progress in CMB Lensing Power Spectrum Measurements 2011-now! (+Pol.)! Planck, 2.5% precision! Planck! •  Rapid progress – but only just beginning!!
  50. 50. Rapid Progress: ! Upcoming Ground-Based CMB Experiments! 50! ACTPol / SPTPol ! POLARBEAR! AdvACT / SPT3G / PB2! Simons ! Observatory! ^4  CMB! Experiment! Noise! Level! ! !
  51. 51. Rapid Progress: ! Upcoming Ground-Based CMB Experiments! 51! ACTPol / SPTPol ! POLARBEAR! AdvACT / SPT3G / PB2! Simons ! Observatory! [Abazajian++ 2014]! ^4  CMB! Experiment! Noise! Level! CMB! Lensing! Becomes! Increasingly Powerful!!
  52. 52. ACTPol CMB Lensing Dark Matter Map! Now: ACTPol/AdvACT – polarization sensitive ACT! compare older ACT lensing map! [Sherwin et al. 2016]! ! •  New, fast, polarization lensing trispectrum pipeline. Results in a map of the dark matter (w. small-scale noise), 50 degs. across:! ACTPol!
  53. 53. ACTPol/AdvACT – ! Early Lensing Power Spectrum Results! [Sherwin et al. 2016, arXiv:1611.09753]! Amplitude relative to standard cosmology expectation – our lensing is consistent!! ! ! •  Lensing power is ~clean, few % level systematics (+can do more)!
  54. 54. ACTPol/AdvACT – ! Early Lensing Power Spectrum Results! [Sherwin et al. 2016, arXiv:1611.09753]! Amplitude relative to standard cosmology expectation – our lensing is consistent!! ! ! •  Constraint: ! X m⌫ < 396meV (95%C.L.)
  55. 55. ! ! ! •  Previously analyzed map – less than 10% of our data!! ! Now: Very Large ACTPol/AdvACT Lensing Maps! N.B. multiplied by mask weight > stripe!
  56. 56. ! ! ! •  Total observed through 2016: 15000 sq. deg. (1st release 500). >50 to <10uK-arcmin – working on lensing extraction now!! ! Now: Very Large ACTPol/AdvACT Lensing Maps! N.B. multiplied by mask weight > stripe! BOSS-N (~3000 sq. deg.) lens map (noisy) - preliminary!!   Sky projected to cylinder!
  57. 57. ! ! ! ! Preliminary Data Run on Small Sub-field! •  Early lensing run on 500 square degrees of deep data.! ! ! !
  58. 58. 58! Preliminary Data Run on Small Sub-field! ~16 sigma on small part of sky! caveat:! many approximations!
  59. 59. ACTPol/AdvACT – Next Paper (2018):! Expect around 3% precision (30-40 sigma)! [Sherwin++ in prep.]! c.f. lower limit, >60meV! •  4000-12000 square degrees, 170 million pixels, temperature and polarization – lensing analysis is a challenge! •  Potential to independently test Planck – e.g. Mv, tensions (?) in high vs. low z structure, H0…! ! [van Engelen++ in prep.]! ( X m⌫) ⇠ 100 meV
  60. 60. ALMA! ACT! CLASS! POLARBEAR!Existing! Notional Pads for Simons Observatory Phase 2 and CMB S4! Simons Observatory! Notional Simons Observatory Phase 1 ! Power! Control !Vehicle s! •  Next generation, funded CMB experiment, 2020-! •  Combines ACT, POLARBEAR collaborations!
  61. 61. 61!
  62. 62. 62!
  63. 63. The Future: Simons Observatory and CMB Stage-IV ! Precision Lensing Power Spectra! Errors inflated by 10x (for display)!! ( X m⌫) ⇠ 20meV•  Will determine unknown neutrino mass in any scenario! c.f. limit, >60meV! (Simons Obs.! / CMB-S4)! Simons Observatory: <1% precise lensing, half sky ! (2020-2025); CMB-S4: ~0.2% precise!
  64. 64. •  CMB lensing maps are unique probes of mass at high z>1! ! ! ! ! ! ! ! ! ! •  Can correlate maps of luminous objects (galaxies, quasars, gas) with lensing/dark matter maps (z~0.5-5, peak z~2)! Great Potential in Astrophysics for Correlating Galaxies, Quasars… with CMB Lensing! Contours: CMB lensing! Color: Density of infrared galaxies! [SPT, Holder++ 2013]!
  65. 65. •  Correlation restores distance / redshift information. ! •  Can probe structure growth and probe DE, … (w. sample variance cancellation!)! ! Structure growth! Redshift! Great Potential in Cosmology for Correlating Galaxies, Quasars… with CMB Lensing!
  66. 66. Rapid Progress in CMB Lensing Measurements! •  Working to solve challenges with students and S.O. lensing group! ! •  Many challenges will be solved with novel theoretical work! ! *   *   *   *  -­‐  B.  Sherwin  playing  a  leading  role  in  analysis  /  planning   Signal-to-noise ratio for temperature and polarization expts. ! *   *   *   now   •  Improved estimators! •  Higher order corrections! •  Astrophysical and instrumental systematics! (…)! [e.g., Sherwin, Boehm, Hill in prep., Boehm, Schmittfull, Sherwin 2016;]! [Horowitz, Ferraro, Sherwin 2017]!
  67. 67. Example Challenge I: ! Astrophysical Systematics! •  Multiplicative and additive systematic biases from bi-/ trispectra of foregrounds! ! •  Typical picture: when nothing is done, ~few percent effect. Multifrequency data and estimator “hardening” should make these unobservable! ! •  …But work still required for new high-precision regimes and polarization!! ! [Sherwin++ in prep. 2016b]! [Liu, Hill, Sherwin++ 2016]! [van Engelen++ 2013, Osborne+ +2013]! N-­‐body  simulated  CMB  lensing  
  68. 68. •  CMB lensing map assumed linear & Gaussian, but it is not!! ! ! •  Structure formation non-linear: neglect gives %-level bias! 68! big cluster! N-body simulated lensing! Gaussian lensing! [Boehm, Schmittfull, Sherwin 2016]! Example Challenge II: ! The Impact of Non-linear Structure ! [Sherwin, Boehm, Liu, Hill in prep.]! N-body simulated CMB lensing! Gaussian CMB lensing! Cdd ` ⇠ h ˜T ˜T ˜T0 ˜T0 i ⇠ hTTT0 T0 i + hT,ijdidjTT0 ,kdkT0 i
  69. 69. time (+ distance light travels!)! Lensing of CMB lets us map dark matter to study neutrino mass +… ! CMB light! Recap! CMB Lensing dark matter map: a signal to study neutrinos, +… CMB!
  70. 70. time (+ distance light travels!)! But if we are interested in the early universe! Now lensing is a problem!! CMB light! CMB Lensing as Noise for Early Universe Cosmology
  71. 71. Outline! •  Introduction to CMB lensing: mapping cosmic dark matter! •  Lensing as a powerful signal for measuring neutrino masses (+…)! •  Lensing as noise for studying inflation and the early universe! 71!
  72. 72. Big Questions •  What happened at the beginning?! ! •  What expanded and flattened the universe?! •  What set up the first fluctuations in density (that turned into galaxies)?! !
  73. 73. Inflation CMB! •  Inflation: initial accelerated cosmic expansion. ! ! •  Creates the initial differences in density (>galaxies) from primordial quantum vacuum fluctuations!! !
  74. 74. Inflation CMB! •  Inflation: initial accelerated cosmic expansion. ! ! •  Good evidence for idea – but we don’t know for sure! ! •  Many (simple) models make inflationary gravity waves*! ! ! *N.B. Some other models also produce GWs!
  75. 75. Inflation CMB! ! •  Probe physics at ultra-high energy (at the doorstep of the Planck scale)! ! ! •  The strength of the waves - tensor-to- scalar ratio r - tells us about the energy at which inflation happened! ! ! N.B. Even improved "! upper limits interesting. ! !
  76. 76. Inflation •  Leaves a characteristic pattern in the CMB polarization! ! ! ! ! CMB!
  77. 77. CMB Polarization Basics! •  Any polarization map can be decomposed into E and B mode fields! •  B-mode: contains signals from inflation, if there! [Image credit: CMBPol]! 77! B mode map! E mode map! ~known physics! new inflation physics!
  78. 78. 10°   78! B   E   B-mode polarization: no background from better known physics! *ignoring  lensing  for  now   CMB B-polarization with no inflationary signal!
  79. 79. 10°   79! B   E   *ignoring  lensing  for  now   CMB B-polarization with no inflationary signal! B-mode polarization: no background from better known physics!
  80. 80. 10°   80! B   E   See signal clearly as there is no background! ! B-modes are a “null channel”! *ignoring  lensing  and  dust  for  now   CMB B-polarization* with small inflationary signal!
  81. 81. Lensed CMB B-Polarization! 10°   81! B   E   Gravitational lensing converts E- to B- polarization! B ⇠ E ⇤ d
  82. 82. Lensed CMB B-Polarization! 10°   82! B   E   Lensing-B noise obscures the inflation signal in the early universe! ! ! ! ! This has already begun to limit constraints!! B ⇠ E ⇤ d Gravitational lensing converts E- to B- polarization!
  83. 83. Future: Simons Observatory / CMB-S4 Error Budget for Measuring Inflationary Grav. Wave Signal! error from instrument noise only (1uK-arcmin)! 1-sigma! Error! On ! Strength! Of ! Inflation! Signal! [i.e. σ(r)]! ! !
  84. 84. error from instrument noise only (1uK-arcmin)! error including lensing noise! Removing lensing is essential for future experiments!!!!!! %   1-sigma! Error! On ! Strength! Of ! Inflation! Signal! [i.e. σ(r)]! ! ! Future: Simons Observatory / CMB-S4 Error Budget for Measuring Inflationary Grav. Wave Signal!
  85. 85. error from instrument noise only (1uK-arcmin)! error including lensing noise! Removing lensing is essential for future experiments!!!!!! %   1-sigma! Error! On ! Strength! Of ! Inflation! Signal! [i.e. σ(r)]! ! ! Future: Simons Observatory / CMB-S4 Error Budget for Measuring Inflationary Grav. Wave Signal! •  Reduction in error is essential to ruling out broad class of large-field inflation models (with super-Planckian field range) ! "– or confirming one of them!!
  86. 86. Delensing the CMB: Lensing Removal! 10°   86! B   E   Gravitational lensing converts E- to B- polarization!
  87. 87. Delensing the CMB: Lensing Removal! 10°   87! B   E   Know lensing, so can reverse it (=delens) and remove lensing from the B-modes! delensing! Gravitational lensing converts E- to B- polarization!
  88. 88. 10°   88! B   E   Delensing the CMB: Lensing Removal!
  89. 89. New Method: Cosmic Infrared Background Delensing! error from instrument noise only (1uK-arcmin)! error with full lensing noise! %! CIB delensing! [Sherwin, Schmittfull 2015]! 1-sigma! Error! On ! Strength! Of ! Inflation! Signal! [i.e. σ(r)]! ! !
  90. 90. New Method: Cosmic Infrared Background Delensing! error from instrument noise only (1uK-arcmin)! error with full lensing noise! %! CIB delensing! -  use maps of cosmic infrared background (CIB) [=galaxy emission] to infer and remove the lensing (used by SPT/BICEP now, main method for LiteBIRD satellite)! [Sherwin, Schmittfull 2015]! 1-sigma! Error! On ! Strength! Of ! Inflation! Signal! [i.e. σ(r)]! ! !
  91. 91. New Method: Cosmic Infrared Background Delensing! error from instrument noise only (1uK-arcmin)! error with full lensing noise! %! CIB delensing! -  use maps of cosmic infrared background (CIB) [=galaxy emission] to infer and remove the lensing (used by SPT/BICEP now, main method for LiteBIRD satellite)! -  make multitracer delensing map! [Sherwin, Schmittfull 2015]! 1-sigma! Error! On ! Strength! Of ! Inflation! Signal! [i.e. σ(r)]! ! ! [Yu, Sherwin, Hill 2017]!
  92. 92. New Method: Cosmic Infrared Background Delensing! error from instrument noise only (1uK-arcmin)! error with full lensing noise! %! CIB delensing! -  use maps of cosmic infrared background (CIB) [=galaxy emission] to infer and remove the lensing (used by SPT/BICEP now, main method for LiteBIRD satellite)! -  make multitracer delensing map! [Sherwin, Schmittfull 2015]! 1-sigma! Error! On ! Strength! Of ! Inflation! Signal! [i.e. σ(r)]! ! ! [Yu, Sherwin, Hill 2017]!
  93. 93. Demonstrating Delensing with (Temp.) Data! Planck CMB Temperature Data ! - lensed, so blurred (cartoon)! Delensed! Planck CMB Temperature Data! (sharper) ! “Lensing Map” from Cosmic Infrared Background! [Larsen, Challinor, Sherwin, Mak 2016]! [Sherwin, Schmittfull 2015]! Reverse Lensing! Deflections!
  94. 94. [Larsen, Challinor, Sherwin, Mak 2016]! [Sherwin, Schmittfull 2015]! Checking Success of Delensing – ! Lensing in CMB Temperature Power Spectrum! CMB Temperature Power Spectrum [uK2]! 1 / angular scale!
  95. 95. [Larsen, Challinor, Sherwin, Mak 2016]! [Sherwin, Schmittfull 2015]! Checking Success of Delensing – ! Lensing in CMB Temperature Power Spectrum! Lensing blurs out features / wiggles in the power. Use to show de-lensing!! ! ! ! ! (effect x10 shown)! CMB Temperature Power Spectrum [uK2]! 1 / angular scale!
  96. 96. CMB Temperature Power [uK2]! 1 / angular scale! Planck CMB Temp. Data ! Delensed! Planck CMB Temp. Data ! Reverse Lensing! Deflections! “Lensing Map” from Cosmic Infrared Background! take difference of power spectrum after delensing ! –! before delensing! Demonstrating Delensing with (Temp.) Data!
  97. 97. Demonstrating Delensing: ! Difference of Delensed - Lensed Temp. Spectra! Red line shows expected un-blurring of the CMB (De- lensing sharpens features)! ! ! ! ! ! ! ! ! ! Flat / zero if lensing removal not working!
  98. 98. Demonstrating Delensing: ! Difference of Lensed and Delensed Temp. Spectra! [Larsen, Challinor, Sherwin, Mak 2016]! [Sherwin, Schmittfull 2015]! Planck data result! 16 sigma detection!
  99. 99. [Larsen, Challinor, Sherwin, Mak 2016]! [Sherwin, Schmittfull 2015]! Planck data result! 16 sigma detection! First Demonstration of Delensing in Data – it works!! !
  100. 100. ! •  SO/CMB-S4: Can discover / constrain much smaller inflation (r~0.001) signals by delensing! ! ! •  Excellent delensing is crucial for future CMB – more research needed, but method should work!! Great Potential: ! Simons Observatory / CMB-S4 Delensing! error, instrument noise only! no delensing! CMB Stage-IV delensing (r~0.001)! %   1-sigma! Error! On ! Strength! Of ! Inflation! Signal! [i.e. σ(r)]! ! !
  101. 101. Future B Mode Map – ! Lensing-Dominated! 10°   101! B  
  102. 102. Delensed B Map – Inflation Signal?! 10°   102! B   a signal from the beginning of the universe?!
  103. 103. Summary! •  With new lensing and delensing analyses, CMB lensing has rapidly progressed. With new experiments (AdvACT / Simons Observatory / CMB-S4) and advances in theory, it will soon be even more powerful!! ! •  With upcoming CMB lensing, we will! –  determine neutrino masses (+study dark energy / astrophysics…)! –  enable powerful probes of inflation and the early universe! –  map all the mass and dark matter in the observable universe!
  104. 104. Summary! Thanks for your attention!! •  With new lensing and delensing analyses, CMB lensing has rapidly progressed. With new experiments (AdvACT / Simons Observatory / CMB-S4) and advances in theory, it will soon be even more powerful!! ! •  With upcoming CMB lensing, we will! –  determine neutrino masses (+study dark energy / astrophysics…)! –  enable powerful probes of inflation and the early universe! –  map all the mass and dark matter in the observable universe! ! Also happy to talk about my work on other areas in cosmology theory / data analysis:! Baryon Acoustic Oscillations! Large scale structure theory! New approaches to galactic dust removal ! New methods in cluster cosmology +…! !
  105. 105. Bonus  slides…  
  106. 106. Backup Slides! 107!
  107. 107. CMB Lensing + lensing auto
  108. 108. •  Lensing maps probe matter density, projected over a wide redshift range peaking at z~2:! ! ! ! ! ! Properties of Future / S4 CMB Lensing Maps!
  109. 109. ACTPol Lensing! 110!
  110. 110. ACTPol Lensing! 111!
  111. 111. ACTPol Lensing! 112!
  112. 112. ACTPol Lensing! 113!
  113. 113. 0.0 0.4 0.8 1.2 1.6 ⌦m 0.50 0.75 1.00 1.25 8 ACT+BAO KIDS ACTPol – Early Lensing Power Spectrum Results ! 114! •  We are consistent with Planck – mild tension with KiDS?! [Sherwin et al. 2016]!matter density! sizeoffluctuations!
  114. 114. Example: Biases from Non-Linear Large Scale Structure! 115! ! •  Higher order terms in lensing estimator (theory 8pt. function)! ! [Boehm, Schmittfull, Sherwin 2016; Sherwin, Boehm++ in prep.]! lensing signal! neglected higher order correction! (will soon matter!)! theory!
  115. 115. Example: Biases from Non-Linear Large Scale Structure! 116! ! •  Higher order terms in lensing estimator (ray-traced N-body sim.)! ! [Boehm, Schmittfull, Sherwin 2016; Sherwin, Boehm++ in prep.]! lensing signal! neglected higher order correction! (will soon matter!)! simulation!
  116. 116. CMB Lensing Systematics! •  Multiplicative and additive biases from bi/trispectra of foregrounds (+lensing itself) ! ! •  Typical picture: when nothing is done, ~few percent effect.! ! •  Multifrequency data and estimator “hardening” should make these unobservable – but work still required for new regimes! [Sherwin++  in  prep.  2016b]   [Liu,  Hill,  Sherwin++  2016]   [van  Engelen++  2013,  Osborne+ +2013]   N-­‐body  simulated  CMB  lensing  
  117. 117. CMB Lensing Cross-correlations
  118. 118. •  Lensing maps probe matter density, projected over a wide redshift range peaking at z~2:! ! •  Information clean: mainly on linear or quasi-linear scales! ! Properties of Future / S4 CMB Lensing Maps! [S4  Science  Book]  
  119. 119. •  SO/CMB S4 (wide survey – half sky?) could target overlap with lots of upcoming and future surveys:! •  Wide range of applications: Astrophysics at high-z, modified gravity, non-Gaussianity, r via delensing… ! What science can we target with ! CMB lensing + LSS?!
  120. 120. •  Astrophysics: Cross-correlations give a new window on high-z, probing relation of dark matter to tracers to get:! ! ! •  Cosmology: CMB lensing can be used to calibrate systematic / galaxy biases in lensing and galaxy surveys! Why cross-correlate CMB lensing with matter tracers?! - Quasar halo properties, evolution, activity (lensing x quasars)! - Bias of galaxies and evolution (lensing x galaxies)! - Star-formation history (e.g. lensing x Cosmic Infrared Background)! - Baryon-dark matter relation (lensing x Sz or Ly-alpha)! [e.g. Sherwin et al. 2012; Ferrarro et al 2015; POLARBEAR 2014b; van Engelen, Sherwin et al. 2015, Hill+Spergel 2014]! 121! ⇥|d(l)| q⇤ (l0 )⇤ = (2⇥)2 Cdq l (l0 l) Cross-­‐power  spectrum  tracer  map  lensing  map  
  121. 121. 122! Lots of Recent Work on CMB Lensing Correlations! 122! ACTPol x Planck CIB! [v.Engelen, Sherwin++ 2015]! First lensing from individual halos (CMASS)! [Madhavach eril++ incl. Sherwin 2015]! Planck x WISE! [Ferraro, Sherwin 2015]! POLARBEAR pol. lensing x! Herschel! [Sherwin corr. auth., 15]!
  122. 122. Example Astrophysical Cross-correlation: ! Quasars x CMB lensing! •  Lensing depends on the matter distribution. QSOs trace the matter distribution, and their redshift distribution matches the lensing kernel.! •  This implies both are correlated! 123! A  quasar  density   map   CMB Lensing Kernel! QSO redshift distribution!
  123. 123. Example Astrophysical Cross-correlation: ! Quasars x CMB lensing! •  This implies both are correlated! 124! A  quasar  density   map   Figure  from   Geach  et  al.  2014   quasar  density   CMB  lensing  
  124. 124.   Cross-power with SDSS photometric quasars:! 4 sigma detection! ! Constraint on bias: ! b(z~1.4)=2.5 ± 0.6 (or halo mass)! ! DiPompeo et al. 2015: extend this to obscured quasars, compare different populations. (Obscured quasars seem more biased; may live in higher-mass halos?)! ! [Sherwin, Das, Hajian et al. 2012 125! First Measurement:! Quasar-CMB lensing Cross-correlation! Cdq amplitude determined by bias! Cdq
  125. 125. •  Astrophysics: Cross-correlations give a new window on high-z, probing relation of dark matter to tracers to get:! ! ! •  Cosmology: CMB lensing can be used to calibrate systematic / galaxy biases in lensing and galaxy surveys! Why cross-correlate CMB lensing with matter tracers?! [e.g. Sherwin et al. 2012; Ferrarro et al 2015; POLARBEAR 2014b; van Engelen, Sherwin et al. 2015, Hill+Spergel 2014]! 126! ⇥|d(l)| q⇤ (l0 )⇤ = (2⇥)2 Cdq l (l0 l) Cross-­‐power  spectrum  tracer  map  lensing  map  
  126. 126. ! Optical Weak Lensing x CMB Lensing! 127! CFHT (CS82) ! galaxy lensing! "X ! ACT CMB Lensing! detected at 4.2 sigma!     [Hand, Das, Leautheaud, Sherwin et al 2015]! •  Can cross-correlate CMB lensing with another kind of lensing measurement: galaxy weak lensing (also a direct mass probe). First detection with ACT.!  = r · d/2 l3 Cdd l/4
  127. 127. Near Future: ! CMB Lensing x Weak Lensing as a Calibrator! 128! •  Example: AdvancedACT x LSST forecast, 100 sigma…! ! •  Use CMB lensing as a calibrator for systematic biases!! •  Dark energy figure of merit much improved! l3 Cdd l/4
  128. 128. CMB Lensing As a Weak Lensing Bias Calibrator! •  Future combinations for systematics calibration are very promising for dark energy and neutrino mass! ! ! ! •  Dark energy FoM: joint analysis, factor of 2 improvement! Core  x  Euclid  Weak  Lensing  [S4  similar]   [Kitching,  Heavens,  Das  2014]  
  129. 129. Near Future, AdvancedACT and CMB Stage IV: ! Great Potential for Cross-Correlation Science! •  Extremely powerful lensing maps over much of the sky, with lots of overlap with other surveys!! •  Useful for astrophysics and weak lensing calibration! (near) full sky lensing mass map!
  130. 130. Bonus  slides…   Neutrino synergy and axion constraints! !
  131. 131. 133!
  132. 132. Bonus  slides…   Light Particles! !
  133. 133. Light Particles and Cosmology! •  Cosmic Neutrino Background: in radiation era, very large part of the energy density - 41% of total!! •  Influences expansion rate H (as extra form of radiation): ! ! ! 136!
  134. 134. Light Particles and Cosmology! •  Cosmic Neutrino Background: in radiation era, very large part of the energy density - 41% of total!! •  Influences expansion rate H (as extra form of radiation): ! ! ! ! •  Energy density parameterized via number of effective neutrino species Neff. Measure via CMB! –  Measure this with Planck:! –  So what? We have Z-decay measurements.! 137!
  135. 135. Neff from Cosmology:! A Universal Probe for Light Relics! •  Not just sensitive to particles with the SM couplings of neutrinos! •  Gravity sees everything: cosmology probes all that is neutrino like (radiation, free-streaming)! •  Can hunt for any new light (relativistic, weakly coupled) particles!! ! ! 138!
  136. 136. History of an Extra Light Particle! •  At high energies, weakly interacting particle is produced in thermal equilibrium. It freezes out at Tfreeze-out. At first, ΔNeff~1.! ! •  Universe cools. Phase transition! (e.g. muons/anti- muons annihilate).! ! ! 139!
  137. 137. History of an Extra Light Particle! •  At high energies, weakly interacting particle is produced in thermal equilibrium. It freezes out at Tfreeze-out. At first, ΔNeff~1.! •  Universe cools. Phase transition! (e.g. muons/anti- muons annihilate).! •  Annihilating particles dump energy into photons not particle. ΔNeff goes DOWN for every phase transition after freeze out.! 140! Impact on energy gets diluted !
  138. 138. A Particle Freezes Out. ! How Much Neff Does it Contribute?! •  Freeze out late / low energy: " "ΔNeff ~1! ! 141!
  139. 139. ! •  Here, some muons (e,g.) will annihilate after freeze out: ΔNeff ~0.5! ! 142! [Baumann++ 2015]! A Particle Freezes Out. ! How Much Neff Does it Contribute?!
  140. 140. ! •  At high freeze-out temperature, the particle misses out on lots of energy from the QCD phase transition, so ΔNeff is very small.! 143! A Particle Freezes Out. ! How Much Neff Does it Contribute?!
  141. 141. Neff: What is the Target?! ! ! ! ! ! ! ! ! ! •  If we can measure this: target sensitivity, can see any new light particle that was ever in equilibrium (out to reheating temp.!)! 144!
  142. 142. Probing Neff in the CMB Power Spectra! •  Change in early expansion rate > change in diffusion time > small change in damping seen in CMB power spectrum. ! •  Also: small shift in phases (free-streaming). Delensing helps! ! 145! Cl TT   multipole  l  0   2000   [Hou++ 2013]!
  143. 143. Challenges / Requirements: ! High Precision Small-scale CMB Spectra! ! •  Requirement to hit targets: Very low noise (~uK’) and large sky areas (fsky~1)! •  Good beam systematics control! •  Or lower noise: 2 sigma, room for improvement! 146!
  144. 144. Bonus  slides…   Cosmology from Non-Gaussian SZ Statistics!
  145. 145. ACT Data: Measuring Skewness (<T3>) due to tSZ! tSZ Decrements! Observed CMB Temperature! IR Sources removed! First detection (5 sigma):! Wilson, Sherwin, Hill et al (2012)!
  146. 146. First Cosmological and Cluster Physics Constraints from the Data! •  Can show: skewness proportional to σ8 10.5 (c.f. power spec. σ8 7)! •  Obtain constraint on σ8 from this measurement! •  In future, constrain cluster physics with skewness/power spec. combination! Hill & Sherwin (2012)!
  147. 147. Binned ACT 148 GHz PDF!
  148. 148. ACT 220 GHz PDF!
  149. 149. Best Fit Model and Constraints! •  New theory and data analysis framework developed to model, measure, and extract cosmology from full PDF! •  Next steps: add lensing information!
  150. 150. Likelihood for Amplitude of Structure!
  151. 151. Bonus  slides…   ACT I Lensing Power!
  152. 152. Bonus  slides…   CIB  Delensing  
  153. 153. JHU CAS Seminar! 156!B. D. Sherwin - CMB Lensing with ACT and ACTPOL!
  154. 154. CMB  lensing  is  a  probe   of  the  projected   mass  distribution   1)  Reconstruct  lensing  from   changes  in  background  CMB   Problem:  need  high   resolution,  low  noise,   polarized  data  for  delensing   To Delens, Need To Measure Lensing - How?! 157! 2)  Estimate  lensing   from  Large  Scale   Structure  tracers  of   lensing,  e.g.  CIB    = Z dzW(z) (z)
  155. 155. Cross-correlations have found ! excellent LSS tracers of lensing! •  CMB  lensing  κ  traces   same  mass  distribution   δ  as  large-­‐scale   structure  tracers   •  Best  lensing  proxy   found:  cosmic  infrared   background  (CIB).   •  Diffuse  emission  from   dusty  star-­‐forming   galaxies     [Planck  2015;  van  Engelen,  Sherwin  et   al.  2014]   high-­‐significance  lensing-­‐ CIB  cross-­‐correlation   CI l  = Z dzW(z) (z)
  156. 156. The Cosmic Infrared Background: ! An Excellent Lensing Tracer! •  ~80%    correlated  with   lensing!     •  Due  to  similar  high-­‐ redshift  origin  as  CMB   lensing,  from  z~2                   Redshi]  origin  of  CIB   Redshi]  origin  of  CMB  Lensing   Planck  lens  deflection  data   stacked  on  CIB  bright  spot  
  157. 157. Simple idea: use (Planck) CIB maps ! as lensing tracers to delens! Planck  CIB  map  at  857  GHz  Planck  CIB  map  at  545  GHz   +  Planck  maps  at  217  GHz,  353  GHz  
  158. 158. Delensing The CMB! measured  B  map  –  tensors  +  lensing   •  How  to  reduce  lensing  noise?       •  Delensing:  make  Blensing  map   from  E+κ  and  subtract:  B  –  Blensing   •  How  do  we  use  a  CIB  map,  I,  to   make  a  lensing  estimate?     es`mate  of  lensing  B  (from  k+E)   _   subtract   lensing   es`mate     from  CIB,  I   E  mode  map   deflect   ˆBlens (r) ⇠ hCBB,lens l + NBB,lens l il<100 B
  159. 159. How to Delens Using the CIB - I! •  To  use  CIB  as  proxy   for  lensing:   normalize  with   function  f,  then   construct  lensing  B   estimate   •  Choose  weight  f   such  that  residual   delensed  B-­‐mode   is  minimized:  f   depends  only  on   observables     min[CB ˆBlens l ] ! f = CI l CII l ˆBlens CIB = Z d2 l0 (2⇡)2 E(l0 )f(l0 , l)I(l l0 ) CIB  map   CIB-­‐lensing  cross-­‐power   CIB  power  
  160. 160. ! •  Scaled CIB : best current lensing map over most scales. Example with Planck 545 GHz:! •  Use this map to estimate lensing B-mode, subtract from data:! ! How to Delens Using the CIB - II! fl ⇥ Il B ˆBlens CIB
  161. 161. CIB-­‐lensing  correla`ons   which  scales  ma*er  most?   Delensing The CMB with the CIB: ! Forecasting Performance!   •  Error  reduction   depends  on  how   much  B-­‐mode   power  is  removed     •  Find  that  CIB   delensing  reduces   B-­‐mode  power  by  a   factor     Where       [Sherwin,  Schmibull  2015]   ⇢ = CI l q C l CII l (1 ⇢2 )
  162. 162. Delensing with the CIB: Single Frequencies! 165! •  Good delensing performance! original  B-­‐mode  power   delensed  B-­‐mode  power  
  163. 163. •  Error  is  reduced  as  lensing  B-­‐mode  power  is  removed       •  Define  delensing  improvement  factor  (how  much  is  any   detection’s  signal-­‐to-­‐noise  boosted?)       Quantifying Delensing Performance: How Much are Constraints on r Improved by Delensing?! ↵ ⌘ 0(r) delensed(r) = hCBB,lens l + NBB l [ P ]il<100 hCBB,res l [ P ] + NBB l [ P ]il<100 Noise  Level  Noise  Power  Delensed  Residual   B-­‐Power   (r) ⇠ hCBB,lens l + NBB,lens l il<100 CBB,res l = Z d2 l0 (2⇡)2 W2 CEE l C l l0 (1 ⇢2 l l0 ) [Smith  et  al.  2012]  
  164. 164. Expected CIB Delensing Improvement Factor! 167! •  Plot: factor by which the signal-to- noise is increased by CIB delensing! •  Up to 2.2 improvement with public, available data! •  Corresponds to 2.22 larger survey.! ! instrumental  noise  level   [Sherwin,  Schmibull  2015]  
  165. 165. Expected CIB Delensing Improvement Factor! 168! •  Plot: factor by which the signal-to- noise is increased by CIB delensing! •  Up to 2.2 improvement with public, available data! •  Corresponds to 2.22 larger survey.! ! Keck  Array  Now:  Equivalent  to  having  800  instead  of  400  square  degrees  
  166. 166. 169! •  Example: SPT/ POLARBEAR + CIB, delensing Keck Array! •  Derive optimal combination: large improvements when including CIB.! •  Powerful combination for delensing with current data!  add  CIB   Combined  Tracers  for  Delensing:     CIB  +  External  Lensing  Reconstruction   [Sherwin,  Schmibull  2015]  
  167. 167. A Potential Problem: Uncertain CIB Spectra! 170! •  Say we have a measurement of CIB delensed B-mode power. Now constrain r, using model for delensed B- mode power:! ! ! ! •  Problem: residual lensing B-mode power depends on the CIB spectra! If CIB spectra are poorly constrained, this can be confused with r.! •  With Planck measurements of , do we know the CIB spectra well enough?! CI l
  168. 168. Robust CIB Delensing, with ! CIB Bandpowers as Nuisance Parameters! 171! ! •  Don’t assume CIB spectra known: parametrize CIB generally, constrain with Planck+BB! •  Constrain r marginalized over CIB spectra, i.e., their parameters ai! •  Fisher matrix formalism: marginalizing over CIB spectra does not degrade delensing performance!! ! CIB  bandpowers  ai  CI l l a1   a2   a3   a4  
  169. 169. ! ! ! Current CIB Maps: A Robust Delensing Tracer! fl ⇥ Il
  170. 170. Null Test: (Anti-)Delensing with ! Rotated, Uncorrelated CIB Maps ! Very  Preliminary   (errors  actually  larger)  

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