We search for the signature of parity-violating physics in the cosmic microwave background, called cosmic birefringence, using the Planck data release 4. We initially find a birefringence angle of ...β=0.30°±0.11° (68% C.L.) for nearly full-sky data. The values of β decrease as we enlarge the Galactic mask, which can be interpreted as the effect of polarized foreground emission. Two independent ways to model this effect are used to mitigate the systematic impact on β for different sky fractions. We choose not to assign cosmological significance to the measured value of β until we improve our knowledge of the foreground polarization.
We present constraints on the tensor-to-scalar ratio
r
using
Planck
data. We use the latest release of
Planck
maps, processed with the
NPIPE
code, which produces calibrated frequency maps in ...temperature and polarisation for all
Planck
channels from 30 GHz to 857 GHz using the same pipeline. We computed constraints on
r
using the
BB
angular power spectrum, and we also discuss constraints coming from the
TT
spectrum. Given
Planck
’s noise level, the
TT
spectrum gives constraints on
r
that are cosmic-variance limited (with
σ
r
= 0.093), but we show that the marginalised posterior peaks towards negative values of
r
at about the 1.2
σ
level. We derived
Planck
constraints using the
BB
power spectrum at both large angular scales (the ‘reionisation bump’) and intermediate angular scales (the ‘recombination bump’) from
ℓ
= 2 to 150 and find a stronger constraint than that from
TT
, with
σ
r
= 0.069. The
Planck
BB
spectrum shows no systematic bias and is compatible with zero, given both the statistical noise and the systematic uncertainties. The likelihood analysis using
B
modes yields the constraint
r
< 0.158 at 95% confidence using more than 50% of the sky. This upper limit tightens to
r
< 0.069 when
Planck
EE
,
BB
, and
EB
power spectra are combined consistently, and it tightens further to
r
< 0.056 when the
Planck
TT
power spectrum is included in the combination. Finally, combining
Planck
with BICEP2/Keck 2015 data yields an upper limit of
r
< 0.044.
We perform a metastudy of recently published redshift space distortion (RSD) measurements of the cosmological growth rate, f(z)σ8(z). We analyze the latest results from the 6dFGS, BOSS, LRG, WiggleZ, ...and VIPERS galaxy redshift surveys, and compare the measurements to expectations from Planck. In this Letter we point out that the RSD measurements are consistently lower than the values expected from Planck, and the relative scatter between the RSD measurements is lower than expected. A full resolution of this issue may require a more robust treatment of nonlinear effects in RSD models, although the trend for a low σ8 agrees with recent constraints on σ8 and Ω(m) from Sunyaev-Zeldovich cluster counts identified in Planck.
The measurement of the large-scale B-mode polarization in the cosmic microwave background (CMB) is a fundamental goal of future CMB experiments. However, because of unprecedented sensitivity, future ...CMB experiments will be much more sensitive to any imperfect modelling of the Galactic foreground polarization in the reconstruction of the primordial B-mode signal. We compare the sensitivity to B-modes of different concepts of CMB satellite missions (LiteBIRD, COrE, COrE+, PRISM, EPIC, PIXIE) in the presence of Galactic foregrounds. In particular, we quantify the impact on the tensor-to-scalar parameter of incorrect foreground modelling in the component separation process. Using Bayesian fitting and Gibbs sampling, we perform the separation of the CMB and Galactic foreground B-modes. The recovered CMB B-mode power spectrum is used to compute the likelihood distribution of the tensor-to-scalar ratio. We focus the analysis to the very large angular scales that can be probed only by CMB space missions, i.e. the reionization bump, where primordial B-modes dominate over spurious B-modes induced by gravitational lensing. We find that fitting a single modified blackbody component for thermal dust where the ‘real’ sky consists of two dust components strongly bias the estimation of the tensor-to-scalar ratio by more than 5σ for the most sensitive experiments. Neglecting in the parametric model the curvature of the synchrotron spectral index may bias the estimated tensor-to-scalar ratio by more than 1σ. For sensitive CMB experiments, omitting in the foreground modelling a 1 per cent polarized spinning dust component may induce a non-negligible bias in the estimated tensor-to-scalar ratio.
We present constraints on the tensor-to-scalar ratio r using a combination of BICEP/Keck 2018 (BK18) and Planck PR4 data allowing us to fit for r consistently with the six parameters of the ΛCDM ...model. We discuss the sensitivity of constraints on r to uncertainties in the ΛCDM parameters as defined by the Planck data. In particular, we are able to derive a constraint on the reionization optical depth τ and thus propagate its uncertainty into the posterior distribution for r. While Planck sensitivity to r is slightly lower than the current ground-based measurements, the combination of Planck with BK18 and baryon-acoustic-oscillation data yields results consistent with r=0 and tightens the constraint to r<0.032 at 95% confidence.
If a single line of sight (LOS) intercepts multiple dust clouds with different spectral energy distributions and magnetic field orientations, then the frequency scaling of each of the Stokes
Q
and
U
...parameters of the thermal dust emission may be different, a phenomenon we refer to as LOS frequency decorrelation. We present first evidence for LOS frequency decorrelation in
Planck
data using independent measurements of neutral-hydrogen (H
I
) emission to probe the 3D structure of the magnetized interstellar medium (ISM). We use H
I
-based measurements of the number of clouds per LOS and the magnetic field orientation in each cloud to select two sets of sightlines: (i) a target sample of pixels that are likely to exhibit LOS frequency decorrelation and (ii) a control sample of pixels that lack complex LOS structure. We test the null hypothesis that LOS frequency decorrelation is not detectable in
Planck
353 and 217 GHz polarization data at high Galactic latitudes. We reject the null hypothesis at high significance based on data that show that the combined effect of polarization angle variation with frequency and depolarization are detected in the target sample. This detection is robust against the choice of cosmic microwave background (CMB) map and map-making pipeline. The observed change in polarization angle due to LOS frequency decorrelation is detectable above the
Planck
noise level. The probability that the detected effect is due to noise alone ranges from 5 × 10
−2
to 4 × 10
−7
, depending on the CMB subtraction algorithm and treatment of residual systematic errors; correcting for residual systematic errors consistently increases the significance of the effect. Within the target sample, the LOS decorrelation effect is stronger for sightlines with more misaligned magnetic fields, as expected. With our sample, we estimate that an intrinsic variation of ~15% in the ratio of 353 to 217 GHz polarized emission between clouds is sufficient to reproduce the measured effect. Our finding underlines the importance of ongoing studies to map the three-dimensional structure of the magnetized and dusty ISM that could ultimately help component separation methods to account for frequency decorrelation effects in CMB polarization studies.
We estimate the spectral index, beta , of polarized synchrotron emission as observed in the 9 yr Wilkinson Microwave Anisotropy Probe sky maps using two methods, linear regression ("T-T plot") and ...maximum likelihood. We partition the sky into 24 disjoint sky regions and evaluate the spectral index for all polarization angles between 0degrees and 85degrees in steps of 5degrees.Averaging over polarization angles,we derive a mean spectral index of beta super(all-sky) = -2.99+ or -0.01 in the frequency range of 23-33 GHz. We find that the synchrotron spectral index steepens by 0.14 from low to high Galactic latitudes, in agreement with previous studies, with mean spectral indices of beta super(plane) = -2.98 + or - 0.01 and beta super(high-lat) = -3.12 + or - 0.04. In addition, we find a significant longitudinal variation along the Galactic plane with a steeper spectral index toward the Galactic center and anticenter than toward the Galactic spiral arms. This can be well modeled by an offset sinusoidal, beta (l) = -2.85 + 0.17 sin(2l - 90degrees). Finally, we study synchrotron emission in the BICEP2 field, in an attempt to understand whether the claimed detection of large-scale B-mode polarization could be explained in terms of synchrotron contamination. Adopting a spectral index of beta = -3.12, typical for high Galactic latitudes, we find that the most likely bias corresponds to about 2% of the reported signal (r = 0.003). The flattest index allowed by the data in this region is beta = -2.5, and under the assumption of a straight power-law frequency spectrum, we find that synchrotron emission can account for at most 20% of the reported BICEP2 signal.
Abstract
We investigate the performance of a simple Bayesian fitting approach to correct the cosmic microwave background (CMB) B-mode polarization for gravitational lensing effects in the recovered ...probability distribution of the tensor-to-scalar ratio. We perform a two-dimensional power spectrum fit of the amplitude of the primordial B modes (tensor-to-scalar ratio, r) and the amplitude of the lensing B modes (parameter Alens), jointly with the estimation of the astrophysical foregrounds including both synchrotron and thermal dust emissions. Using this Bayesian framework, we forecast the ability of the proposed CMB space mission LiteBIRD to constrain r in the presence of realistic lensing and foreground contributions. We compute the joint posterior distribution of r and Alens, which we improve by adopting a prior on Alens taken from the South Pole Telescope (SPT) measurement. As it applies to the power spectrum, this approach cannot mitigate the uncertainty on r that is due to E-mode cosmic variance transferred to B modes by lensing, unlike standard delensing techniques that are performed on maps. However, the method allows us to correct for the bias on r induced by lensing, at the expense of a larger uncertainty due to the increased volume of the parameter space. We quantify, for different values of the tensor-to-scalar ratio, the trade-off between bias correction and increase of uncertainty on r. For LiteBIRD simulations, which include foregrounds and lensing contamination, we find that correcting the foreground-cleaned CMB B-mode power spectrum for the lensing bias, not the lensing cosmic variance, still guarantees a 3σ detection of r = 5 × 10−3. The significance of the detection is increased to 6σ when the current SPT prior on Alens is adopted.
We constrain the spectral index of polarized synchrotron emission,
β
s
, by correlating the recently released 2.3 GHz
S
-Band Polarization All Sky Survey (
S
-PASS) data with the 23 GHz 9-year
...Wilkinson
Microwave Anisotropy Probe (WMAP) sky maps. We subdivide the S-PASS field, which covers the southern ecliptic hemisphere, into 95 15° ×15° regions and estimate the spectral index of polarized synchrotron emission within each region using a simple but robust
T
–
T
plot technique. Three different versions of the S-PASS data are considered, corresponding to: no correction for Faraday rotation; Faraday correction based on the rotation measure model presented by the S-PASS team; or Faraday correction based on a rotation measure model presented by Hutschenreuter and Enßlin. We find that the correlation between S-PASS and WMAP is strongest when applying the S-PASS model. Adopting this correction model, we find that the mean spectral index of polarized synchrotron emission gradually steepens from
β
s
≈ −2.8 at low Galactic latitudes to
β
s
≈ −3.3 at high Galactic latitudes, in good agreement with previously published results. The flat spectral index at the low Galactic latitudes is likely partly due to depolarization effects. Finally, we consider two special cases defined by the BICEP2 and SPIDER fields and obtain mean estimates of
β
BICEP2
= −3.22 ± 0.06 and
β
SPIDER
= −3.21 ± 0.03, respectively. Adopting the bandpass filtered WMAP 23 GHz sky map to only include angular scales between 2° and 10° as a spatial template, we constrain the root-mean-square synchrotron polarization amplitude to be less than 0.03
μ
K (0.009
μ
K) at 90 GHz (150 GHz) for the BICEP2 field, corresponding roughly to a tensor-to-scalar ratio of
r
≲ 0.02 (
r
≲ 0.005). Very similar constraints are obtained for the SPIDER field. A comparison with a similar analysis performed in the 23–33 GHz range suggests a flattening of about Δ
β
s
∼ 0.1 ± 0.2 from low to higher frequencies, but with no statistical significance due to high uncertainties.
LiteBIRD is a candidate satellite for a strategic large mission of JAXA. With its expected launch in the middle of the 2020s with a H3 rocket, LiteBIRD plans to map the polarization of the cosmic ...microwave background radiation over the full sky with unprecedented precision. The full success of LiteBIRD is to achieve
δ
r
<
0.001
, where
δ
r
is the total error on the tensor-to-scalar ratio
r
. The required angular coverage corresponds to
2
≤
ℓ
≤
200
, where
ℓ
is the multipole moment. This allows us to test well-motivated cosmic inflation models. Full-sky surveys for 3 years at a Lagrangian point L2 will be carried out for 15 frequency bands between 34 and 448 GHz with two telescopes to achieve the total sensitivity of 2.5
μ
K arcmin with a typical angular resolution of 0.5
∘
at 150 GHz. Each telescope is equipped with a half-wave plate system for polarization signal modulation and a focal plane filled with polarization-sensitive TES bolometers. A cryogenic system provides a 100 mK base temperature for the focal planes and 2 K and 5 K stages for optical components.
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