data analysis and cosmological results from the ﬁrst...

Data analysis and cosmological results from the first observational campaigns of the POLARBEAR

experiment

Julien PelotonUniversity of Sussex

Rencontres de MoriondMarch 22nd 2016

1

Julien Peloton Moriond 2016

CMB and its anisotropies

• Oldest accessible light in the Universe (z~1100)

• Nearly perfect isotropic radiation: black body spectrum (3 K)

• Small anisotropies in temperature (I): ΔT/T0~10-5

• Polarised anisotropies (Q&U): ~10%

• Source of the unique information on age, composition, and curvature of the Universe, strong evidence for dark matter and complementary evidence for dark energy.


Weak lensing of the CMB

3

• Deflection angle —> gradient of the lensing potential.

• 3 main effects: CMB power spectra are smoothed, lensing B-modes are generated and lensed CMB fluctuations are anisotropic (non-zero CMB trispectrum due to lensing).

• Probes growth of large-scale structure, and additional estimates of cosmological parameters!

(lensed) T, (lensed) E-modes,

primordial B-modes,lensing B-modes

T, E-modes, primordial B-modes

Gravitational lensing by large-scale structures!

z~1100 z=0z~2

primordial

lensed

from Planck Collaboration

BB

r=?


Main motivations

4

• Detection of lensing B-modes and lensing potential (polarisation) would validate our comprehension of the structure formation and evolution of the Universe.

• Detection of primordial B-modes would open a new window onto cosmology!

• Both require specific technological developments, and sophisticated data analysis (weak signals among several contaminants!).

• POLARBEAR is one of the current experiments aiming at the detection of both.


POLARBEAR Collaboration


Sky signal

The POLARBEAR experiment

6

•Site

•Atacama desert in Chile (5,200 m)

•Telescope

•Primary mirror 2.5 m

•Beam FWHM ~3.5 arcmin

•Receiver

•HWP at the entrance

•FP temperature 250 mK

•1,274 TES bolometer @ 150 GHz

•NET array ~23 µK.√s

Focal plane

1274 bolometers @ 150 GHz

Cooled to 250mK

300K70K4K0.25K

Receiver

Stepped HWPOptics

Receiver

Slot antenna

TES

1 mm

Pixel

TES

Systematic error control

Sensitivity


1st and 2nd seasons of observation

7

RA23

RA4.5

RA12

PB-1 1st & 2nd season surveys • Deep integration on 3x3 degree patches • Patches selected for: low foreground,

long observation schedule, cross-correlation with other experiments.

Test phase2010

2011Move to Chile

First light2012/01

2012/05 - 2013/061st season

2013/10 - 2014/042nd season

2014/05 - 3rd season

Small patches Small patches Large patch

• We perform constant elevation scans (CES) • Efficient to separate ground and sky

emissions: another mitigation of systematics. Provide a good cross-linking.

• Orthogonal antennas within pixel

Elev

atio

n

Azimuth Path of patch

80°

30°

Ground coordinates

Sky

coor

dina

tes

Sky coordinates Sky coordinates

Sky coordinates

s1+s2

s3

See Josquin’s talk for the future!


From raw data to cosmology: calibration

8

• POLARBEAR is a complex instrument operating in changing environment.

• Frequent calibration is needed to combine the data.

• Four primary instrument properties to be modelled:

• Pointing (Observations of planets and fixed sources)

• Thermal-response (Planets + atmosphere + artificial calibrator measurements)

• Instrument effective beam (Planets + fixed sources)

• Polarisation angle (Taurus A and Centaurus A)1st season beam maps from Jupiter and Saturn

elev

atio

n of

fset

azimuth offset

1st season P map of TauA

elev

atio

n of

fset

azimuth offsetazimuth offset

elev

atio

n of

fset


Atmosphere contamination

9

• CMB observations are affected by atmosphere.

• Modelling the atmosphere and its effects is complex: Errard et al. 2015.

• Atmosphere is the largest contribution: introduce low-frequency noise (low-ell).

• It makes the signal correlated among detectors and in time.

• Differentiating timestreams from the same pixel helps, but it is not sufficient (plus systematic contamination can arise). WHWP can be better, although not perfect.

raw (calibrated)

difference

difference + filtered


Mapmaking: 1011 samples, 105 pixels

10

• Filtered mapmaking

• Flat-sky MASTER power spectrum estimation (Hivon et al 2002) with daily cross-spectra

• Unbiased mapmaking (iterative)

• Curve sky pure-pseudo power-spectrum estimation (Smith et al 2006, Grain et al 2009)

• Unbiased mapmaking (full)

• Curve sky pure-pseudo power-spectrum estimation (Smith et al 2006, Grain et al 2009)

Cross check and validation

Cross check and validation

Fast, biased rendition of the sky

Unbiased, but slower and depends on

convergence

Unbiased, full information on the covariance matrix but much (much) slower!

Filtering is done serially, pixels uncorrelated

Filters are orthogonalised, full

covariance

�ATFA

�s = ATFd

�ATFA

�si = ATFd

�ATN�1A

�s = ATFd

coming soon!

Intensity

-200

200

iterations0 99

Filtering is done serially, pixels uncorrelated

noise < 10uk.arcminfiltered filtered


The CMB as observed by Planck and POLARBEAR

POLARBEAR relative to Planck:

• POLARBEAR sees the same hot and cold spots as Planck in intensity, but at a better resolution (3.5’).

• We cross-correlate POLARBEAR maps with Planck maps to estimate the absolute calibration for POLARBEAR maps.

• POLARBEAR (s1) is 4x deeper on small fraction of the sky (6 uk.arcmin vs 27 uk.arcmin).

11

8

PB (s1)Planck (SMICA)

Intensity map


Instrumental systematic control

12

Beam, gain, crosstalk, weather, Sun, … (I->P leakage)

Polarisation angle mismatch (E->B) and pointing mismatch, beam, …

(“lensing-like” effects)

freq

uenc

y

𝓁10 100 1,000

30 GHz

300 GHz

4,000

reio

niza

tion

lens

ing

BB spectrum

prim

ordi

al PB-1

B-modes signal is extremely weak: beware of instrumental contamination!

Two main frameworks used: Null tests, end-to-end simulations using measured instrument characteristics.

Data analysis is done “blindly”.


Ab-initio simulation pipeline

13

Input cosmology (BB=0)Input beam

Theory B-modesSum of all systematic terms

Binned Statistical Uncertainty• Boresight & diff pointing• Differential beamsize• Polarization angle• Differential ellipticity• HWP-dependent gain• HWP-independent gain• Electrical crosstalk• Gain drift

TT

EE

TE


1st season PB angular CMB power-spectra

14

Excellent agreement with LCDM model. Excellent agreement with other

measurements at intermediate and small-scales.

TT

EE

TE

Model for dusty galaxies + radio sources (Reichardt et al 2012, Seiffert et al 2007) + lensing

𝓁


BB angular power spectrum

15

BB Angular power spectrumApJ 794, 171 (2014)

-0.4

-0.2

0

0.2

0.4

0.6

0.8

0 500 1000 1500 2000 2500

l(l+1

)ClBB

/(2�)

(!K2 )

Multipole Moment, ell�

⇥(⇥+1)C

BB

`/(2�

)(µK

2) • 4 bandpowers: 500-2100.

• Uncertainties include: calibration, sample variance and noise

• Model-independent rejection of no B-power at 2σ (including syst)

• 2σ confirmation of the lensing amplitude wrt fiducial model (including syst)

BB


Other results from the 1st campaign

16

from POLARBEARFlux

from Hershel

from POLARBEAR from POLARBEAR

Lensing reconstruction naturally leads to higher-point statistics:

• Start with observed polarisation P(n) • Apply quadratic estimator d(l) to CMB data • Estimate the deflection power spectrum Cdd(l) • Estimator for Cdd(l) is a 4-point estimator in the CMB

• Start with observed polarisation P(n) and galaxy count g(n)

• Apply quadratic estimator d(l) to CMB data • Estimate the deflection power spectrum Cdg(l) • Estimator for Cdg(l) is a 3-point estimator in the CMB

e.g EBxg, EExg, etc…

e.g EBxEB, EBxEE, etc…


CMB x CIB

17

• CMB lensing reconstruction yields a map of projected density

• This can be cross-correlated with galaxy density maps to learn how galaxies relate to the underlying dark matter.

• Flux map of Herschel @ 500 um (H-ATLAS survey from the Herschel-SPIRE instrument).

• Combine EB and EE estimators to increase the SNR.

• Systematics do not correlate

• Results

2.3σ evidence for the B-mode lensing

Evidence for gravitational lensing of the CMB polarisation at 4.0σ

Galaxy cross-correlation:PRL 112, 131302 (2014)

(from EB and EE) I from Herschel


CMB x CMB

18

Deflection power spectrum: PRL 113, 021301 (2014)

• Can also use CMB polarisation lensing only

• Combine EB and EE estimator to increase the SNR: EExEB and EBxEB.

• Novel measurement! (polarisation)

• Careful checks for systematics

• Results

4.2σ rejection of the null hypothesis (including sys)

Lensing amplitude (LCDM):

5

−4

−2

0

2

4

100 500 1000 2000L(L+

1)CLdd

/2!["10

#7]

L

<EEEB>

100 500 1000 2000L

<EBEB>

FIG. 2: Measured polarization lensing power spectra for each of Polarbear’s three patches, for both lensing estimators⟨EEEB⟩ (left) and ⟨EBEB⟩ (right). The lensing signal predicted by the ΛCDM model is shown as the solid black curve. Themeasured lensing power spectra are shown for each patch in dark green (RA23), blue (RA12) and magenta (RA4.5), respectivelyand are offset in L slightly for clarity. The patch-combined lensing power spectrum is shown in red.

−2

0

2

100 500 1000 2000

L(L+

1)CLdd

/2!["10

#7]

L

Unlensed

−2

0

2

100 500 1000 2000

L(L+

1)CLdd

/2!["10

#7]

L

Unlensed

−2

0

2

100 500 1000 2000

L(L+

1)CLdd

/2!["10

#7]

L

Unlensed

−2

0

2

100 500 1000 2000

L(L+

1)CLdd

/2!["10

#7]

L

Unlensed

−2

0

2

100 500 1000 2000

L(L+

1)CLdd

/2!["10

#7]

L

Unlensed

100 500 1000 2000L

Lensed

100 500 1000 2000L

Lensed

100 500 1000 2000L

Lensed

100 500 1000 2000L

Lensed

0

0.5

1

−1.0 0 1.0 2.0 3.0

Lik

elih

ood

A

0

0.5

1

−1.0 0 1.0 2.0 3.0

Lik

elih

ood

A

FIG. 3: Polarization lensing power spectra co-added from the three patches and two estimators are shown in red. The lensingsignal predicted by the ΛCDM model is shown as the dashed black curve in the left panel and the solid black curve in theright panel, respectively. The polarization lensing power spectrum ⟨EEEB⟩ is in blue and ⟨EBEB⟩ dark green. Left: A 4.2σrejection of the null hypothesis of no lensing. These data indicate a lensing amplitude A = 1.37± 0.30± 0.13 normalized to thefiducial ΛCDM value. Right: The same data, assuming the existence of gravitational lensing to calculate error bars, includingsample variance and including the covariance between ⟨EEEB⟩ and ⟨EBEB⟩. In this case, the lensing amplitude is measuredas A = 1.06 ± 0.47+0.35

−0.31 , corresponding to 54% uncertainty on the CddL power spectrum (27% uncertainty on the amplitude of

matter fluctuations). The histograms of the amplitudes A from 500 unlensed and lensed simulations are shown in the insetboxes.

is detected at 3.2σ significance statistically.

The right panel of Fig. 3 assumes the predicted amountof gravitational lensing in the ΛCDM model. In thiscase, the ⟨EEEB⟩ and ⟨EBEB⟩ estimators are corre-lated, which changes the optimal linear combination ofthe two, and requires that lensing sample variance beincluded in the band-power uncertainties. Under thisassumption, the amplitude of the polarization lensingpower spectrum is measured to be A = 1.06± 0.47+0.35

−0.31.The last term gives an estimate of systematic error. SinceA is a measure of power and depends quadratically onthe amplitude of the matter fluctuations, we measure theamplitude with 27% error. The measured signal tracesall the B -modes at sub-degree scales. This signal is pre-sumably due to gravitational lensing of CMB, becauseother possible sources, such as gravitational waves, po-larization cosmic rotation [35] and patchy reionizationare expected to be small at these scales.

Conclusions: We report the evidence for gravitationallensing, including the presence of lensing B-modes, di-rectly from CMB polarization measurements. Thesemeasurements reject the absence of polarization lensing

at a significance of 4.2σ. We have performed null testsand have simulated systematics errors using the mea-sured properties of our instrument, and we find no sig-nificant contamination. Our measurements are in goodagreement with predictions based on the combination ofthe ΛCDM model and basic gravitational physics. Thiswork represents an early step in the characterization ofCMB polarization lensing after the precise temperaturelensing measurement from Planck. The novel techniqueof polarization lensing will allow future experiments to gobeyond Planck in signal-to-noise and scientific returns.Future measurements will exploit this powerful cosmo-logical probe to constrain neutrino masses [17] and de-lens CMB observations in order to more precisely probeB -modes from primordial gravitational waves.

Acknowledgments: This work was supported by the Di-rector, Office of Science, Office of High Energy Physics,of the U.S. Department of Energy under Contract No.DE- AC02-05CH11231. The computational resourcesrequired for this work were accessed via the Glidein-WMS [36] on the Open Science Grid [37]. This projectused the CAMB and FFTW software packages. Cal-

5

−4

−2

0

2

4

100 500 1000 2000

L(L+

1)CLdd

/2!["10

#7]

L

<EEEB>

100 500 1000 2000L

<EBEB>

FIG. 2: Measured polarization lensing power spectra for each of Polarbear’s three patches, for both lensing estimators⟨EEEB⟩ (left) and ⟨EBEB⟩ (right). The lensing signal predicted by the ΛCDM model is shown as the solid black curve. Themeasured lensing power spectra are shown for each patch in dark green (RA23), blue (RA12) and magenta (RA4.5), respectivelyand are offset in L slightly for clarity. The patch-combined lensing power spectrum is shown in red.

−2

0

2

100 500 1000 2000

L(L+

1)CLdd

/2!["10

#7]

L

Unlensed

−2

0

2

100 500 1000 2000

L(L+

1)CLdd

/2!["10

#7]

L

Unlensed

−2

0

2

100 500 1000 2000

L(L+

1)CLdd

/2!["10

#7]

L

Unlensed

−2

0

2

100 500 1000 2000

L(L+

1)CLdd

/2!["10

#7]

L

Unlensed

−2

0

2

100 500 1000 2000

L(L+

1)CLdd

/2!["10

#7]

L

Unlensed

100 500 1000 2000L

Lensed

100 500 1000 2000L

Lensed

100 500 1000 2000L

Lensed

100 500 1000 2000L

Lensed

0

0.5

1

−1.0 0 1.0 2.0 3.0

Lik

elih

ood

A

0

0.5

1

−1.0 0 1.0 2.0 3.0

Lik

elih

ood

A

FIG. 3: Polarization lensing power spectra co-added from the three patches and two estimators are shown in red. The lensingsignal predicted by the ΛCDM model is shown as the dashed black curve in the left panel and the solid black curve in theright panel, respectively. The polarization lensing power spectrum ⟨EEEB⟩ is in blue and ⟨EBEB⟩ dark green. Left: A 4.2σrejection of the null hypothesis of no lensing. These data indicate a lensing amplitude A = 1.37± 0.30± 0.13 normalized to thefiducial ΛCDM value. Right: The same data, assuming the existence of gravitational lensing to calculate error bars, includingsample variance and including the covariance between ⟨EEEB⟩ and ⟨EBEB⟩. In this case, the lensing amplitude is measuredas A = 1.06 ± 0.47+0.35

−0.31 , corresponding to 54% uncertainty on the CddL power spectrum (27% uncertainty on the amplitude of

matter fluctuations). The histograms of the amplitudes A from 500 unlensed and lensed simulations are shown in the insetboxes.

is detected at 3.2σ significance statistically.

The right panel of Fig. 3 assumes the predicted amountof gravitational lensing in the ΛCDM model. In thiscase, the ⟨EEEB⟩ and ⟨EBEB⟩ estimators are corre-lated, which changes the optimal linear combination ofthe two, and requires that lensing sample variance beincluded in the band-power uncertainties. Under thisassumption, the amplitude of the polarization lensingpower spectrum is measured to be A = 1.06± 0.47+0.35

−0.31.The last term gives an estimate of systematic error. SinceA is a measure of power and depends quadratically onthe amplitude of the matter fluctuations, we measure theamplitude with 27% error. The measured signal tracesall the B -modes at sub-degree scales. This signal is pre-sumably due to gravitational lensing of CMB, becauseother possible sources, such as gravitational waves, po-larization cosmic rotation [35] and patchy reionizationare expected to be small at these scales.

Conclusions: We report the evidence for gravitationallensing, including the presence of lensing B-modes, di-rectly from CMB polarization measurements. Thesemeasurements reject the absence of polarization lensing

at a significance of 4.2σ. We have performed null testsand have simulated systematics errors using the mea-sured properties of our instrument, and we find no sig-nificant contamination. Our measurements are in goodagreement with predictions based on the combination ofthe ΛCDM model and basic gravitational physics. Thiswork represents an early step in the characterization ofCMB polarization lensing after the precise temperaturelensing measurement from Planck. The novel techniqueof polarization lensing will allow future experiments to gobeyond Planck in signal-to-noise and scientific returns.Future measurements will exploit this powerful cosmo-logical probe to constrain neutrino masses [17] and de-lens CMB observations in order to more precisely probeB -modes from primordial gravitational waves.

Acknowledgments: This work was supported by the Di-rector, Office of Science, Office of High Energy Physics,of the U.S. Department of Energy under Contract No.DE- AC02-05CH11231. The computational resourcesrequired for this work were accessed via the Glidein-WMS [36] on the Open Science Grid [37]. This projectused the CAMB and FFTW software packages. Cal-

(from EB and EE)

(from EB and EE)

A = 1.06± 0.47+0.35�0.31

(stat) (sys)


Primordial magnetic fields/Cosmic birefringence

• PMFs and parity-violating physics lead to birefringence, i.e. rotation of polarisation converting E-modes to B-modes.

• The rotation angle alpha along the line of sight:

19

• Use quadratic estimator (EBEB):

0 500 1000 1500 2000L

-10

-5

0

5

10

C↵↵

L[⇥

10�

4 deg

2 ]

CoaddedRA23RA12RA4.5

• Amplitude of an equivalent PMF interpreted from the anisotropic rotation power spectrum < 93 nG (95% C.L.) (Planck 2015: <1380 nG @ 95% C.L.)

• Constraints on cosmic birefringence and primordial magnetic fields from 1st season using B-modes spectrum: B1Mpc < 3.9 nG (95% C.L.) (Planck 2015: B1Mpc < 4.4 nG @ 95% C.L.)

(B1Mpc: magnetic field strength smoothed over 1 Mpc)


Towards the 2nd season of observation

• Include first 2 years of observation (Full small patch analysis).

• Improved calibration, especially analyses using planets.

• Re-calibration of the 1st season, and more robust data selection.

• Improved mapmaking techniques.

• …

• Analysis is finishing.

20


Towards the 3rd season of observation• We have observed 30x20 deg2 patch for

2 years using continuously rotating HWP.

• Analysis ongoing.

• We are evaluating systematic effects especially beam systematics induced by HWP at prime focus.

21

27 cm

WHWP modulates polarisation to reduce 1/f noise due to atmospheric fluctuations

Cross-Polarisation patterns from TauA observations:

Figures from S. Takakura


CMBxCIB

CMBxCMB

22

CMB investigations continue to provide a unique window on the physics of both the early Universe and the growth of large-scale structure.

There is a lot of potential in the gravitational lensing of the CMB, and efforts to extract this signal using polarisation data are underway. The era for precision measurements of lensing B-modes has started (cross-correlation and direct measurements). Full 1st and 2nd season results will soon be out, stay tuned! Large patch analysis: analysis ongoing.

Conclusion


Thanks!

23

+ Planck 2015

Status early 2016

data analysis and cosmological results from the ﬁrst...

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