CMB polarization systematics due to beam asymmetry: Impact on inflationary science

Shimon, Meir; Keating, Brian; Ponthieu, N.; Hivon, E.

doi:10.1103/physrevd.77.083003

Cited by 121 publications

(211 citation statements)

References 28 publications

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“…Therefore, the major axes in the simulations were varied around the azimuthal direction by 10 • rms to roughly simulate the observed alignment trend within each pair. Analytic calculations show, and these simulations verify, that the expected false BB power scales as the square of differential beam size or ellipticity and as the fourth power of the beam size (Shimon et al 2008).…”

Section: Beam Characterizationmentioning

confidence: 90%

Characterization of the Bicep Telescope for High-Precision Cosmic Microwave Background Polarimetry

Takahashi¹,

Ade²,

Barkats³

et al. 2010

ApJ

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The Background Imaging of Cosmic Extragalactic Polarization (Bicep) experiment was designed specifically to search for the signature of inflationary gravitational waves in the polarization of the cosmic microwave background (CMB). Using a novel small-aperture refractor and 49 pairs of polarization-sensitive bolometers, Bicep has completed three years of successful observations at the South Pole beginning in 2006 February. To constrain the amplitude of the inflationary B-mode polarization, which is expected to be at least 7 orders of magnitude fainter than the 3 K CMB intensity, precise control of systematic effects is essential. This paper describes the characterization of potential systematic errors for the Bicep experiment, supplementing a companion paper on the initial cosmological results. Using the analysis pipelines for the experiment, we have simulated the impact of systematic errors on the B-mode polarization measurement. Guided by these simulations, we have established benchmarks for the characterization of critical instrumental properties including bolometer relative gains, beam mismatch, polarization orientation, telescope pointing, sidelobes, thermal stability, and timestream noise model. A comparison of the benchmarks with the measured values shows that we have characterized the instrument adequately to ensure that systematic errors do not limit Bicep's two-year results, and identifies which future refinements are likely necessary to probe inflationary B-mode polarization down to levels below a tensor-to-scalar ratio r = 0.1.

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Section: Beam Characterizationmentioning

confidence: 90%

Characterization of the Bicep Telescope for High-Precision Cosmic Microwave Background Polarimetry

Takahashi¹,

Ade²,

Barkats³

et al. 2010

ApJ

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“…Beam systematics affect the EB spectra in a different way than TB spectra [33,34]. As a result, the scale dependence of the beam systematic polarization will imply a different effective rotation angle in the TB spectrum versus the EB spectrum, for a fixed l−range.…”

Section: B Differential Beam Effectsmentioning

confidence: 99%

“…Though the differential beam size effect can leak temperature to polarization, due to circular symmetry it will not break the parity of the underlying sky and thus cannot generate the parity-odd TB and EB modes [33].…”

Section: Differential Beam Sizementioning

confidence: 99%

Self-calibration of BICEP1 three-year data and constraints on astrophysical polarization rotation

Kaufman¹,

Miller²,

Shimon³

et al. 2014

Phys. Rev. D

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Cosmic microwave background (CMB) polarimeters aspire to measure the faint B-mode signature predicted to arise from inflationary gravitational waves. They also have the potential to constrain cosmic birefringence, rotation of the polarization of the CMB arising from parity-violating physics, which would produce nonzero expectation values for the CMB's temperature to B-mode correlation (TB) and E-mode to B-mode correlation (EB) spectra. However, instrumental systematic effects can also cause these TB and EB correlations to be nonzero. In particular, an overall miscalibration of the polarization orientation of the detectors produces TB and EB spectra which are degenerate with isotropic cosmological birefringence, while also introducing a small but predictable bias on the BB spectrum. We find that BICEP1 three-year spectra, which use our standard calibration of detector polarization angles from a dielectric sheet, are consistent with a polarization rotation of α ¼ −2.77°AE 0.86°ðstatisticalÞ AE 1.3°ðsystematicÞ. We have revised the estimate of systematic error on the polarization rotation angle from the two-year analysis by comparing multiple calibration methods. We also account for the (negligible) impact of measured beam systematic effects. We investigate the polarization rotation for the BICEP1 100 GHz and 150 GHz bands separately to investigate theoretical models that produce frequency-dependent cosmic birefringence. We find no evidence in the data supporting either of these models or Faraday rotation of the CMB polarization by the Milky Way galaxy's magnetic field. If we assume that there is no cosmic birefringence, we can use * jkaufman@physics.ucsd.edu PHYSICAL REVIEW D 89, 062006 (2014) 1550-7998=2014=89(6)=062006 (11) 062006-1 © 2014 American Physical Society the TB and EB spectra to calibrate detector polarization orientations, thus reducing bias of the cosmological B-mode spectrum from leaked E-modes due to possible polarization orientation miscalibration. After applying this "self-calibration" process, we find that the upper limit on the tensor-to-scalar ratio decreases slightly, from r < 0.70 to r < 0.65 at 95% confidence.

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“…In CMB practice there are numerous other potential sources of such leakages. For instance, they can arise from instrument limitations, such as beam mismatch [52] or polarimeter orientation uncertainty [53], or be generated by data processing, say, via time-domain filtering [4,14]. Such leakages would also have an effect on estimated Bmode power spectrum.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Detecting the tensor-to-scalar ratio with the pure pseudospectrum reconstruction ofB-mode

Ferté¹,

Peloton²,

Grain³

et al. 2015

Phys. Rev. D

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B-mode of polarized anisotropies of the cosmic microwave background is a unique and nearly direct probe of primordial inflation, which can constrain the amplitude of the primordial gravity waves. However, its detection and precise measurement is made difficult by a minute amplitude of the signal, which has to be discerned from many contributions of non-cosmological origin and reliable estimated in the presence of numerous sources of statistical uncertainties. Among these latter, the Eto-B leakage, arising as a result of partial sky coverage, has been found to play a key and potentially fundamental role in determining the possible statistical significance with which the primordial Bmode signal can be detected. In this work we employ the pure-pseudo formalism devised to minimise the effects of the leakage on the variance of power spectrum estimates and discuss the limits on the tensor-to-scalar ratio, r, that could be realistically set by current and forthcoming measurements of the B-mode angular power spectrum. We compare those with the results obtained using other approaches: naïve mode-counting, minimum-variance quadratic estimators, and re-visit the question of optimizing the sky coverage of small-scale, suborbital experiments in order to maximize the statistical significance of the detection of r. We show that the optimized sky coverage is largely insensitive to the adopted approach at least for reasonably compact sky patches. We find, however, that the mode-counting overestimates the detection significance by a factor ∼ 1.17 as compared to the lossless maximum variance approach and by a factor ∼ 1.25 as compared to the lossy pure pseudospectrum estimator. In a second time, we consider more realistic experimental configurations. With a pure pseudospectrum reconstruction of B-modes and considering only statistical uncertainties, we find that a detection of r ∼ 0.11, r ∼ 0.0051 and r ∼ 0.0026 at 99% of confidence level is within the reach of current sub-orbital experiments, future arrays of ground-based telescopes and a satellite mission, respectively. This means that an array of telescopes could be sufficient to discriminate between large-and small-field models of inflation, even if the E-to-B leakage is consistently included but accounted for in the analysis. However, a satellite mission will be required to distinguish between different small-field models depending on the number of e-folds.

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CMB polarization systematics due to beam asymmetry: Impact on inflationary science

Cited by 121 publications

References 28 publications

Characterization of the Bicep Telescope for High-Precision Cosmic Microwave Background Polarimetry

Characterization of the Bicep Telescope for High-Precision Cosmic Microwave Background Polarimetry

Self-calibration of BICEP1 three-year data and constraints on astrophysical polarization rotation

Detecting the tensor-to-scalar ratio with the pure pseudospectrum reconstruction ofB-mode

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