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A tremendous international effort is currently dedicated to observing the so-called primordial B modes of the Cosmic Microwave Background (CMB) polarisation. If measured, this faint signal imprinted by the primordial gravitational wave background, would be an evidence of the inflation epoch and quantify its energy scale, providing a rigorous test of fundamental physics far beyond the reach of accelerators. At the unprecedented sensitivity level that the new generation of CMB experiments aims to reach, every uncontrolled instrumental systematic effect will potentially result in an analysis bias that is larger than the much sought-after CMB B -mode signal. The absolute calibration of the polarisation angle is particularly important in this sense, as any associated error will end up in a leakage from the much larger E modes into B modes. The Crab nebula (Tau A), with its bright microwave synchrotron emission, is one of the few objects in the sky that can be used as absolute polarisation calibrators. In this communication, we review the best current constraints on its polarization angle from 23 to 353 GHz, at typical angular scales for CMB observations, from WMAP, IRAM XPOL, Planck and NIKA data. We will show that these polarization angle measurements are compatible with a constant angle and we will present a study of the uncertainty on this mean angle, making different considerations on how to combine the individual measurement errors. For each of the cases, the potential impact on the CMB B -mode spectrum and on the recovered r parameter will be explored.

Inflation is the leading theory of the first instant of the universe. Inflation, which postulates that the universe underwent a period of rapid expansion an instant after its birth, provides convincing explanation for cosmological observations. Recent advancements in detector technology have opened opportunities to explore primordial gravitational waves generated by the inflation through “B-mode” (divergent-free) polarization pattern embedded in the cosmic microwave background anisotropies. If detected, these signals would provide strong evidence for inflation, point to the correct model for inflation, and open a window to physics at ultra-high energies. LiteBIRD is a satellite mission with a goal of detecting degree-and-larger-angular-scale B-mode polarization. LiteBIRD will observe at the second Lagrange point with a 400 mm diameter telescope and 2622 detectors. It will survey the entire sky with 15 frequency bands from 40 to 400 GHz to measure and subtract foregrounds. The US LiteBIRD team is proposing to deliver sub-Kelvin instruments that include detectors and readout electronics. A lenslet-coupled sinuous antenna array will cover low-frequency bands (40–235 GHz) with four frequency arrangements of trichroic pixels. An orthomode-transducer-coupled corrugated horn array will cover high-frequency bands (280–402 GHz) with three types of single frequency detectors. The detectors will be made with transition edge sensor (TES) bolometers cooled to a 100 milli-Kelvin base temperature by an adiabatic demagnetization refrigerator. The TES bolometers will be read out using digital frequency multiplexing with Superconducting QUantum Interference Device (SQUID) amplifiers. Up to 78 bolometers will be multiplexed with a single SQUID amplifier. We report on the sub-Kelvin instrument design and ongoing developments for the LiteBIRD mission.

© 2018 Springer Science+Business Media, LLC, part of Springer Nature The high-frequency telescope for LiteBIRD is designed with refractive and reflective optics. In order to improve sensitivity, this paper suggests the new optical configurations of the HFT which have approximately 7 times larger focal planes than that of the original design. The sensitivities of both the designs are compared, and the requirement of anti-reflection (AR) coating on the lens for the refractive option is derived. We also present the simulation result of a sub-wavelength AR structure on both surfaces of silicon, which shows a band-averaged reflection of 1.1–3.2% at 101–448 GHz.

A tremendous international effort is currently dedicated to observing the so-called primordial B modes of the Cosmic Microwave Background (CMB) polarisation. If measured, this faint signal imprinted by the primordial gravitational wave background, would be an evidence of the inflation epoch and quantify its energy scale, providing a rigorous test of fundamental physics far beyond the reach of accelerators. At the unprecedented sensitivity level that the new generation of CMB experiments aims to reach, every uncontrolled instrumental systematic effect will potentially result in an analysis bias that is larger than the much sought-after CMB B-mode signal. The absolute calibration of the polarisation angle is particularly important in this sense, as any associated error will end up in a leakage from the much larger E modes into B modes. The Crab nebula (Tau A), with its bright microwave synchrotron emission, is one of the few objects in the sky that can be used as absolute polarisation calibrators. In this communication, we review the best current constraints on its polarisation angle from 23 to 353 GHz, at typical angular scales for CMB observations, from WMAP, IRAM XPOL, Planck and NIKA data. We will show that these polarisation angle measurements are compatible with a constant angle and we will present a study of the uncertainty on this mean angle, making different considerations on how to combine the individual measurement errors. For each of the cases, the potential impact on the CMB B-mode spectrum will be explored.

We present a cross-spectra based approach for the analysis of CMB data at large angular scales to constrain the reionization optical depth \\(\\tau\\), the tensor to scalar ratio \\(r\\) and the amplitude of the primordial scalar perturbations \\(A_s\\). With respect to the pixel-based approach developed so far, using cross-spectra has the unique advantage to eliminate spurious noise bias and to give a better handle over residual systematics, allowing to efficiently combine the cosmological information encoded in cross-frequency or cross-dataset spectra. We present two solutions to deal with the non-Gaussianity of the \\(\\hat{C}_\\ell\\) estimator distributions at large angular scales: the first one relies on an analytical parametrization of the estimator distribution, while the second one is based on modification of the Hamimache\\&Lewis likelihood approximation at large angular scales. The modified HL method (oHL) is powerful and complete. It allows to deal with multipole and mode correlations for a combined temperature and polarization analysis. We validate our likelihoods on numerous simulations that include the realistic noise levels of the \\wmap, \\planck-LFI and \\planck-HFI experiments, demonstrating their validity over a broad range of cross-spectra configurations.

We present cosmological parameter results from the final full-mission Planck measurements of the CMB anisotropies. We find good consistency with the standard spatially-flat 6-parameter \\(\\Lambda\\)CDM cosmology having a power-law spectrum of adiabatic scalar perturbations (denoted \"base \\(\\Lambda\\)CDM\" in this paper), from polarization, temperature, and lensing, separately and in combination. A combined analysis gives dark matter density \\(\\Omega_c h^2 = 0.120\\pm 0.001\\), baryon density \\(\\Omega_b h^2 = 0.0224\\pm 0.0001\\), scalar spectral index \\(n_s = 0.965\\pm 0.004\\), and optical depth \\(\\tau = 0.054\\pm 0.007\\) (in this abstract we quote \\(68\\,\\%\\) confidence regions on measured parameters and \\(95\\,\\%\\) on upper limits). The angular acoustic scale is measured to \\(0.03\\,\\%\\) precision, with \\(100\\theta_*=1.0411\\pm 0.0003\\). These results are only weakly dependent on the cosmological model and remain stable, with somewhat increased errors, in many commonly considered extensions. Assuming the base-\\(\\Lambda\\)CDM cosmology, the inferred late-Universe parameters are: Hubble constant \\(H_0 = (67.4\\pm 0.5)\\)km/s/Mpc; matter density parameter \\(\\Omega_m = 0.315\\pm 0.007\\); and matter fluctuation amplitude \\(\\sigma_8 = 0.811\\pm 0.006\\). We find no compelling evidence for extensions to the base-\\(\\Lambda\\)CDM model. Combining with BAO we constrain the effective extra relativistic degrees of freedom to be \\(N_{\\rm eff} = 2.99\\pm 0.17\\), and the neutrino mass is tightly constrained to \\(\\sum m_\\nu< 0.12\\)eV. The CMB spectra continue to prefer higher lensing amplitudes than predicted in base -\\(\\Lambda\\)CDM at over \\(2\\,\\sigma\\), which pulls some parameters that affect the lensing amplitude away from the base-\\(\\Lambda\\)CDM model; however, this is not supported by the lensing reconstruction or (in models that also change the background geometry) BAO data. (Abridged)

We present full-sky maps of the cosmic microwave background (CMB) and polarized synchrotron and thermal dust emission, derived from the third set of Planck frequency maps. These products have significantly lower contamination from instrumental systematic effects than previous versions. The methodologies used to derive these maps follow those described in earlier papers, adopting four methods (Commander, NILC, SEVEM, and SMICA) to extract the CMB component, as well as three methods (Commander, GNILC, and SMICA) to extract astrophysical components. Our revised CMB temperature maps agree with corresponding products in the Planck 2015 delivery, whereas the polarization maps exhibit significantly lower large-scale power, reflecting the improved data processing described in companion papers; however, the noise properties of the resulting data products are complicated, and the best available end-to-end simulations exhibit relative biases with respect to the data at the few percent level. Using these maps, we are for the first time able to fit the spectral index of thermal dust independently over 3 degree regions. We derive a conservative estimate of the mean spectral index of polarized thermal dust emission of beta_d = 1.55 +/- 0.05, where the uncertainty marginalizes both over all known systematic uncertainties and different estimation techniques. For polarized synchrotron emission, we find a mean spectral index of beta_s = -3.1 +/- 0.1, consistent with previously reported measurements. We note that the current data processing does not allow for construction of unbiased single-bolometer maps, and this limits our ability to extract CO emission and correlated components. The foreground results for intensity derived in this paper therefore do not supersede corresponding Planck 2015 products. For polarization the new results supersede the corresponding 2015 products in all respects.

This paper describes the 2018 Planck CMB likelihoods, following a hybrid approach similar to the 2015 one, with different approximations at low and high multipoles, and implementing several methodological and analysis refinements. With more realistic simulations, and better correction and modelling of systematics, we can now make full use of the High Frequency Instrument polarization data. The low-multipole 100x143 GHz EE cross-spectrum constrains the reionization optical-depth parameter \\(\\tau\\) to better than 15% (in combination with with the other low- and high-\\(\\ell\\) likelihoods). We also update the 2015 baseline low-\\(\\ell\\) joint TEB likelihood based on the Low Frequency Instrument data, which provides a weaker \\(\\tau\\) constraint. At high multipoles, a better model of the temperature-to-polarization leakage and corrections for the effective calibrations of the polarization channels (polarization efficiency or PE) allow us to fully use the polarization spectra, improving the constraints on the \\(\\Lambda\\)CDM parameters by 20 to 30% compared to TT-only constraints. Tests on the modelling of the polarization demonstrate good consistency, with some residual modelling uncertainties, the accuracy of the PE modelling being the main limitation. Using our various tests, simulations, and comparison between different high-\\(\\ell\\) implementations, we estimate the consistency of the results to be better than the 0.5\\(\\sigma\\) level. Minor curiosities already present before (differences between \\(\\ell\\)<800 and \\(\\ell\\)>800 parameters or the preference for more smoothing of the \\(C_\\ell\\) peaks) are shown to be driven by the TT power spectrum and are not significantly modified by the inclusion of polarization. Overall, the legacy Planck CMB likelihoods provide a robust tool for constraining the cosmological model and represent a reference for future CMB observations. (Abridged)

Analysis of the Planck 2018 data set indicates that the statistical properties of the cosmic microwave background (CMB) temperature anisotropies are in excellent agreement with previous studies using the 2013 and 2015 data releases. In particular, they are consistent with the Gaussian predictions of the \\(\\Lambda\\)CDM cosmological model, yet also confirm the presence of several so-called \"anomalies\" on large angular scales. The novelty of the current study, however, lies in being a first attempt at a comprehensive analysis of the statistics of the polarization signal over all angular scales, using either maps of the Stokes parameters, \\(Q\\) and \\(U\\), or the \\(E\\)-mode signal derived from these using a new methodology (which we describe in an appendix). Although remarkable progress has been made in reducing the systematic effects that contaminated the 2015 polarization maps on large angular scales, it is still the case that residual systematics (and our ability to simulate them) can limit some tests of non-Gaussianity and isotropy. However, a detailed set of null tests applied to the maps indicates that these issues do not dominate the analysis on intermediate and large angular scales (i.e., \\(\\ell \\lesssim 400\\)). In this regime, no unambiguous detections of cosmological non-Gaussianity, or of anomalies corresponding to those seen in temperature, are claimed. Notably, the stacking of CMB polarization signals centred on the positions of temperature hot and cold spots exhibits excellent agreement with the \\(\\Lambda\\)CDM cosmological model, and also gives a clear indication of how Planck provides state-of-the-art measurements of CMB temperature and polarization on degree scales.

The data from the Euclid mission will enable the measurement of the photometric redshifts, angular positions, and weak lensing shapes for over a billion galaxies. This large dataset will allow for cosmological analyses using the angular clustering of galaxies and cosmic shear. The cross-correlation (XC) between these probes can tighten constraints and it is therefore important to quantify their impact for Euclid. In this study we carefully quantify the impact of XC not only on the final parameter constraints for different cosmological models, but also on the nuisance parameters. In particular, we aim at understanding the amount of additional information that XC can provide for parameters encoding systematic effects, such as galaxy bias or intrinsic alignments (IA). We follow the formalism presented in Euclid Collaboration: Blanchard et al. (2019) and make use of the codes validated therein. We show that XC improves the dark energy Figure of Merit (FoM) by a factor \\(\\sim 5\\), whilst it also reduces the uncertainties on galaxy bias by \\(\\sim 17\\%\\) and the uncertainties on IA by a factor \\(\\sim 4\\). We observe that the role of XC on the final parameter constraints is qualitatively the same irrespective of the galaxy bias model used. We also show that XC can help in distinguishing between different IA models, and that if IA terms are neglected then this can lead to significant biases on the cosmological parameters. We find that the XC terms are necessary to extract the full information content from the data in future analyses. They help in better constraining the cosmological model, and lead to a better understanding of the systematic effects that contaminate these probes. Furthermore, we find that XC helps in constraining the mean of the photometric-redshift distributions, but it requires a more precise knowledge of this mean in order not to degrade the final FoM. [Abridged]