Measurements of Degree-Scale B-mode Polarization

with BICEP2, Keck Array, and BICEP3

Colin Bischoff, 20 March 2016, Rencontres de Moriond

E-Mode Polarization Pattern

B-Mode Polarization Pattern

CMB Polarization

Amplitude of the gravitational wave signal is parametrized by tensor-to-scalar ratio, r, which is related to the energy scale of inflation.

Other sources of B-mode polarization

Gravitational lensing by large-scale structure converts fraction of primordial E mode to B mode.

Foreground emission: • Synchrotron = low frequency

foreground • Dust = high frequency foreground • Polarized by the Galactic magnetic

field.

TT spectrum

EE spectrum

BB from lensing

BB from inflation, r = 0.001 – 0.1

Target peak of BB spectrum at scales of a

few degrees

CMB Temperature and Polarization Spectra

BICEP3 (2015-)

BICEP-3-Array (2018-)

BICEP2 and Keck Array

Lens

Nylon filterLensNb magnetic shield

Passive thermal filter

Flexible heat straps

Fridge mounting bracketRefrigeratorCamera plate

Focal plane assembly

Opt

ics

tube

Cam

era

tube

1.2 m

• Small aperture cryogenic telescope targeting degree-scale peak of inflationary B modes.

• TES bolometers coupled to phased-array antennas, 256 dual-polarization pixels at 150 GHz.

The BICEP/Keck Collaboration

Elevated Station

Dark Sector

MAPO: Keck DSL: BICEP3, SPT

Amundsen-Scott South Pole Station• High (2800m) and dry site • Exceptionally stable atmosphere • Target field (~1% of the sky) is visible 24 hours/day • Logistical support from US Antarctic Program

Ice Cube

The BICEP/Keck Collaboration

The BICEP/Keck Collaboration

Steffen Richter (BICEP2)

Robert Schwarz (Keck Array) Sam Harrison (BICEP3)

Hans Boenish (BICEP3)

Winter-overs!

BICEP2 + Keck Array 150 GHz maps

Includes data through 2014. Map depth = 50 nK deg (3.0 μK arcmin). Deepest ever maps of degree-scale polarization!

signal maps jackknife (noise) maps

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BICEP2 + Keck Array 150 GHz BB spectrum

• High significance detection of BB power

• Significant excess over lensing spectrum (red curve) at low 𝓵

• Jackknife null test is consistent with zero (blue points)

Multipole, 𝓵

𝓵 (𝓵

+1) C

𝓵 / 2

π [μ

K2 ](data through 2014)

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Detectors Designed to Scale in Frequency

95

150

220

95 GHz

150 GHz

220 GHz

95 GHz detectors installed in 2 of 5 Keck receivers for 2014 observing season

BICEP2 + Keck Array BB auto and cross-spectra

BB

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Multipole, 𝓵

𝓵 (𝓵

+1) C

𝓵 / 2

π [μ

K2 ]

30 GHz

44 GHz

70 GHz

100 GHz

143 GHz

217 GHz

353 GHz

Synchrotron foreground dominates at low frequency

Dust foreground dominates at high frequency

Planck satellite provides full-sky maps of polarization at seven frequencies (also using two low frequency polarization maps from WMAP)

30 GHz

44 GHz

70 GHz

100 GHz

143 GHz

217 GHz

353 GHz

Synchrotron foreground dominates at low frequency

Dust foreground dominates at high frequency

Planck satellite provides full-sky maps of polarization at seven frequencies (also using two low frequency polarization maps from WMAP)

BICEP/Keck field

Selected cross-spectra between BICEP2/Keck and WMAP/Planck

Strong detection of dust in BK 150 GHz x Planck 353 GHz (and to a lesser extent in BK14 150 x Planck 217 GHz)

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𝓵 (𝓵

+1) C

𝓵 / 2

π [μ

K2 ]

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Auto and cross-spectra between BICEP2 + Keck Array and all WMAP/Planck maps

• Statistics for all spectra derived from joint simulations of signal and noise.

• Calculate likelihood of a parametrized model that contains CMB and foreground signals.

• Uses priors on foreground spectral and spatial behavior (derived from Planck maps over larger sky regions).

r

Parameter Constraints

Adust Async

A syn

cA d

ust

L/L m

ax

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r < 0.09 at 95% confidence

Now beats the best constraints

from temperature

data

r Adust Async

A syn

cA d

ust

L/L m

ax

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Keck 95 GHz maps help

break CMB–dust

degeneracy

foreground spectral indices (prior dominated) dust-sync correlation

foreground spatial behavior

Parameter Constraints

BB in

𝓵~8

0 ba

ndpo

wer

, 𝓵 (𝓵

+1) C

𝓵 / 2

π [μ

K2 ]

Nominal band center [GHz]

Summary of current sensitivity

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2015 Keck Array E-mode maps including 220 GHz

Already 3x deeper than Planck 217 GHz

𝜦CDM E modes observed with high S/N at three frequencies!

Zotefoam Window

HDPE Lenses

PT-410 Pulse Tube

He4-He3 Sorption Fridge

HDPE Window

Alumina Lenses

PT-415 Pulse Tube

He4-He3 Sorption Fridge

Reflective Metal-Mesh Filters

26.4 cm Aperture 55 cm Aperture

Keck vs BICEP3 Telescope

Large Area Infrared Shaders

Thin, low loss, high thermal conductivity alumina filters and lenses with epoxy-based antireflection coating

Plug & play detector modules each with 64 pixels at 95 GHz and cold multiplexing electronics.

BICEP3 New Technology

680-mm window, fast optics (f/1.6), FOV ~28° 95 GHz beam FWHM ~0.35°

BICEP3 In Operation!

BICEP3 In Operation!

2015 Keck+BICEP3 operation configuration • Keck Array: 2 receivers @ 95 GHz, 1 @ 150 GHz, 2 @ 220 GHz • BICEP3: Partial focal plane (9 tiles) @ 95 GHz

2016 Keck+BICEP3 operating configuration • Keck Array: 1 receiver @ 150 GHz, 4 @ 220 GHz • BICEP3: Full focal plane (20 tiles) @ 95 GHz

New Data Includes: ● Keck 2015: 95 + 150 + 220 GHz ● BICEP3 2015: 95 GHz

Contours are projected constraints on r and Adust for two hypothetical best-fit points (both consistent with BK14).

Signal model includes pessimistic assumption about synchrotron foreground.

r < 0.041 at 95% confidence — or — Foregrounds only PTE = 0.6%

Projected Parameter Constraints for 2015 Analysis

BICEP3Delensing with

South Pole Telescope (10 meter primary)

BICEP3 (2015-)

BICEP-3-Array (2018-)

photo: Keith Vanderlinde