Measurements of CMB Polarization SPT Keck Array Bicep2 Christian - - PowerPoint PPT Presentation

Christian Reichardt

University of Melbourne

Measurements of CMB Polarization

SPT Bicep2 Keck Array PolarBear in Chile

Outline

• CMB polarization & Gravitational Lensing
• First detection of lensing B-modes
• Future prospects (SPT-3G, Simons Array)

– What are the neutrino masses?

• Energy injection from dark matter
• z ~ O(100): Temperature-polarization

correlation

• z ~ O(107): Spectral Distortion

Things left out

• only touch upon gravity waves from Inflation
• Temperature probes:
• thermal Sunyaev-Zel’dovich effect:
• Competitive constraints on dark energy from

galaxy clusters

• kinetic Sunyaev-Zel’dovich effect (cross-

correlated with optical surveys)

• Test modified gravity models at ~200 Mpc

scales

Temperature is very well measured

CMB is linearly polarized at 10% level by Thompson scattering.

10% Polarized

hot$ hot$ cold$ cold$

Photons/electrons Thompson scatter at last scattering surface Local radiation quadrupole leads to a preferred direction

Net linear polarization!

Polarization direction Electron Oscillation

• Any polarization pattern can be

decomposed into “E” (grad) and “B” (curl) modes

• Density fluctuations at LSS do not

produce “B” modes!

The CMB is polarized

Smith et al 2008

10o

8

B-modes come from:

Inflationary gravity waves Gravitational lensing

T(ˆ n) ! T(ˆ n + rφ(ˆ n))

φ(ˆ n) = −2 Z χ∗ dχ fK(χ∗ − χ) fK(χ∗)fK(χ)Ψ(χˆ n; η0 − χ)

RMS deflection 2.5’; coherent on degree scales

• 1. Low systematic uncertainties:
• Gaussian, well-understood

power spectrum

• Known, unique redshift
• 2. High redshift
• No higher-z source

CMB is a unique lensing source

SPT map of 6% of matter in observable Universe (20 σ)

Weighing the Hubble Volume

work being led by O. Zahn

ACT and SPT temperature measurements are now sample/foreground limited. Only way to get more information is to cover more sky or go to polarization.

Planck map of full sky (30 σ)

Small Changes Big Changes!!!

Effect of Lensing

Gravity wave signal

B-modes very important once noise is below ~ 8 uk-arcmin

Outline

CMB polarization & Gravitational Lensing

• First detection of lensing B-modes
• Future prospects (SPT-3G, Simons Array)

– What are the neutrino masses?

• Energy injection from dark matter
• z ~ O(100): Temperature-polarization

correlation

• z ~ O(107): Spectral Distortion

• Lens reconstruction in polarization can be

thought of as a process of template fitting.

• Cross correlations guard against systematics

φ

E

Blens

Detecting Lensing B-modes

Correlation with the Cosmic Infrared Background (CIB)

• Redshift kernel of

lensing peaks z~2

• Well-matched to CIB

(80% correlation)

Smith+, 2007

Herschel/SPIRE 250, 350, 500 um

• May 2012: Map deepest 100 deg2 of SPT

survey to the confusion limit.

φ

E

Blens

Herschel CIB!

• Lens reconstruction in polarization can be

thought of as a process of template fitting.

• Cross correlations guard against systematics

Detecting Lensing B-modes

Detection of B-mode Polarization in the Cosmic Microwave Background with Data from the South Pole Telescope

SPTpol: First detection of lensing B modes ( 7.7 σ ) Uses three-point EBɸ from SPTpol + Herschel-SPIRE maps of the cosmic infrared background.

E (SPTpol) Density (SPIRE) Predicted B

Duncan Hanson et al., PRL 2013

PolarBear also detects polarized lensing in two ways: 4.0 / 4.2 σ

lensing B-mode Power Spectrum

Consistent results using:

• 90GHz E-modes.
• Temperature-derived E-modes.
• TT, TE, EE, EB lensing

estimators.

• No signal seen using:
• Curl-mode null test.
• E-modes from diff. map.
• B-modes from diff. map.

Angular Frequency (multipole)

Power (µK2 x104)

Not yet a test of gravity waves (GW)

• Cross-correlation eliminates GW signal
• Wrong angular scales (GW in blue region)

Outline

CMB polarization & Gravitational Lensing Lensing B-modes (first detected in 2013)

• Future prospects (SPT-3G, Simons

Array)

– What are the neutrino masses?

• Energy injection from dark matter
• z ~ O(100): Temperature-polarization

correlation

• z ~ O(107): Spectral Distortion

Small Changes Big Changes!!!

Effect of Lensing

Gravity wave signal

B-modes very important once noise is below ~ 8 uk-arcmin

2001: ACBAR 16 detectors 2007: SPT 960 detectors 2012: SPTpol ~1600 detectors 2012: PB 1500 detectors 2016: SPT-3G ~15,200 detectors Simons Array: 30k detectors 2020?: CMB-S4 100,000+ detectors

Detector sensitivity has been limited by photon “shot” noise for last ~15 years; further improvements are made only by making more detectors!

Pol Pol Pol

Stage-2 Stage-3 Stage-4

Go big!

credit: B. Benson

Tech directions

Simons Array

Keck Array

Multichroic pixels Multiplexing Multiple dewars / telescopes

CMB Experimental Stages

2000 2005 2010 2015 2020 10

−4

10

−3

10

−2

10

−1

WMAP Planck

C M B − S 4

Year Approximate raw experimental sensitivity (µK)

Space based experiments Stage−I − ≈ 100 detectors Stage−II − ≈ 1,000 detectors Stage−III − ≈ 10,000 detectors Stage−IV − ≈ 100,000 detectors

Today

Snowmass: CF5 Neutrinos Document arxiv:1309.5383

Stage-IV CMB experiment = CMB-S4 ~200x faster than today’s Stage 2 experiments

e.g., SPTpol POLARBEAR ACTpol e.g., SPT-3G Simons Array Adv ACTpol

Much more to come!

Lensing B-modes have been detected by: SPTpol, POLARBEAR

! 5! t!

0$ 20$ 40$ 60$ 80$ 100$ 120$ 140$ 160$

Signal'to'Noise-on-Lensing-Power-Spectrum-

ACT-1 SPT-1 Planck-1 SPT-full ACT-full SPTpol Polarbear ACTpol SPT-3G Simons Array Adv ACTpol adapted from

• B. Sherwin

Taking data now (Stage 2): SPTpol / POLARBEAR / ACTpol: ~ 45 σ Current best: Planck: 30 σ Data-taking starts ~2016 (Stage 3): SPT-3G / Simons Array / Adv ACTpol: ~ 150 σ

• Stage 4 ~ early 2020s

Stage 2 Stage 3

Neutrinos as seen by Structure

∑mν = 0 eV ∑mν = 0.94 eV k (Mpc-1) P(k) @ z=0 Matter power spectrum today

100 meV changes BB power by up to 5%

mν

Long scales: Faster expansion & clustering cancel (no net change) Short scales: Faster expansion suppresses structure

There are 3-4 sigma ‘detections’ at ~300 meV

Predictions for neutrino masses

Planck + DESI (BAO) Simons + Planck Simons + Planck + DESI (BAO) Also: x1.8 improvement on Neff vs Planck

σ(∑mν)=18 meV

(22 meV for SPT3G)

An aside: Inflation Constraints

Δϕ ¡≳ ¡mpl Δϕ ¡≲ ¡mpl Snowmass: CF5 Inflation Document arxiv:1309.5381

Stage 3: x5-10 better than BICEP2

• Stage 4:

x50 better than BICEP2

• Both stage 3/4

include multiple frequencies for foreground control

1 0.1 0.01 0.001 0.0001 0.00001

BICEP2 r=0.20+0.07-0.05

Outline

CMB polarization & Gravitational Lensing Lensing B-modes (first detected in 2013) Future prospects (SPT-3G, Simons Array)

– What are the neutrino masses?

• Looking for energy injection from

dark matter

• z ~ O(100): Temperature-polarization

correlation

• z ~ O(107): Spectral distortion

Extra O(100) GeV positrons

PAMELA (2008); confirmed by AMS (2013)

AMS collaboration

What could produce these?

• Exotic pulsars?
• Dark matter?
• None of the above.

e± energy [GeV]

from Doug Finkbeiner

Modifies ionization history

• WIMP annihilation/decay injects high-energy particles

& photons into the gas at z~O(100).

10-3 10-2 10-1 1 xe 10 100 1000 100 101 102 103 104 Tmat (K) Redshift Padmanabhan & Finkbeiner 2005

Increases ionization fraction and temperature

from Doug Finkbeiner

Detectable in the CMB

• Increased ionization

fraction broadens “last-scattering” – weakens T-P correlations; strengthens PP correlations

• Measure total

energy injection which constrains WIMP properties

Ruled out by WMAP5 Planck forecast CVL

1 2 3 4 5 6 7 8 9 10 11 12 13

1 XDM µ+µ- 2500 GeV, BF = 2300 2 µ+µ- 1500 GeV, BF = 1100 3 XDM µ+µ- 2500 GeV, BF = 1000 4 XDM e+e- 1000 GeV, BF = 300 5 XDM 4:4:1 1000 GeV, BF = 420 6 e+e- 700 GeV, BF = 220 7 µ+µ- 1500 GeV, BF = 560 8 XDM 1:1:2 1500 GeV, BF = 400 9 XDM µ+µ- 400 GeV, BF = 110 10 µ+µ- 250 GeV, BF = 81 11 W+W- 200 GeV, BF = 66 12 XDM e+e- 150 GeV, BF = 16 13 e+e- 100 GeV, BF = 10

PAMELA/AMS models predict similar energy injection, can be

ruled out with Planck polarization data soon!

Slatyer, et al. 2009

Sampling of PAMELA models from Doug Finkbeiner

Light Dark Matter?

(neutralino/gravitinos)

from Kogut et

• al. 2011

Decay/annihilation add energy in early Universe: 106 < z < 108 Energy release: ΔE ~ΩDM 𝛥Δm Chemical potential: μ ~ ΔE/E Electromagentic Energy Release Lifetime ==> Distortion in the CMB black-body spectrum

BBN limits Plot for gravitinos

Measuring distortion

PIXIE forecast: μ < 1e-8 (95%CL) x10,000 better than COBE/FIRAS from Kogut et

• al. 2011

PIXIE forecast:

PIXIE is a proposed nulling Fourier Transform Spectrometer

• see also PRISM, LiteBird

Also excellent at disentangling foregrounds and inflationary gravity waves

In conclusion

• Exciting time for the cosmic microwave

background

– Lensing polarization signal detected by 2+ experiments; approaching interesting sensitivity for inflationary signal – Opens new window into inflation and structure growth at z~2. – Experiments are improving by leaps and bounds

• POLARBEAR/SPTpol (2012-2015): 1500 detectors
• Simons Array/SPT-3G (2016): 30k/15k detectors
• Stage 4: >100k detectors