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.
Most of the CMB experiments proposed for the next generation aim to detect the Primordial Gravitational Wave Background (PGWB). The fulfillment of this objective depends on our capacity to separate ...Galactic foreground emissions and to delens the secondary B-mode component induced by weak gravitational lensing. Focusing on the latter of these efforts, in this work we briefly review the basic aspects of lensing, and exhaustively compare the performance of current delensing methodologies and implementations within the Born approximation as a preparation for the analysis of the data to come in the following years. Two of the main conclusions that can be drawn from our study are that, for next-generation experiments, delensing efficiency will still be limited by the quality of the data itself rather than by the limitations of current delensing methodologies, and that template delensing within the antilensing approximation will be the optimal (balancing accuracy and computational cost) technique to employ. We then evaluate the delensing capabilities of future experiments (like the Simons Observatory, the CMB Stage-IV, or the LiteBIRD and PICO satellites) by applying that methodology onto numerical simulations of the typical CMB and lensing potential reconstructions that they are expected to produce, and quantify how internal and external delensing will help them to improve their sensitivity to detect the PGWB. We also consider the benefits that a joint analysis of their data would provide.
Abstract
Although interesting in themselves, extragalactic sources emitting in the microwave range (mainly radio-loud active galactic nuclei and dusty galaxies) are also considered a contaminant from ...the point of view of Cosmic Microwave Background (CMB) experiments. These sources appear as unresolved point-like objects in CMB measurements because of the limited resolution of CMB experiments. Amongst other issues, point-like sources are known to obstruct the reconstruction of the lensing potential, and can hinder the detection of the Primordial Gravitational Wave Background for low values of r. Therefore, extragalactic point-source detection and subtraction is a fundamental part of the component separation process necessary to achieve some of the science goals set for the next generation of CMB experiments. As a previous step to their removal, in this work we present a new filter based on steerable wavelets that allows the characterization of the emission of these extragalactic sources. Instead of the usual approach of working in polarization maps of the Stokes' Q and U parameters, the proposed filter operates on E- and B-mode polarization maps. In this way, it benefits from the lower intensity that, both, the CMB, and the galactic foreground emission, present in B-modes to improve its performance. To demonstrate its potential, we have applied the filter to simulations of the future PICO satellite, and we predict that, for the regions of fainter galactic foreground emission in the 30 GHz and 155 GHz bands of PICO, our filter will be able to characterize sources down to a minimum polarization intensity of, respectively, 125 pK and 14 pK. Adopting a Π=0.02 polarization degree, these values correspond to 169 mJy and 288 mJy intensities.
Abstract
The polarization of the cosmic microwave background (CMB) can be used to search for parity-violating processes like that predicted by a Chern-Simons coupling to a light pseudoscalar field. ...Such an interaction rotates
E
modes into
E
modes in the observed CMB signal through an effect known as cosmic birefringence. Even though isotropic birefringence can be confused with the rotation produced by a miscalibration of the detectors' polarization angles, the degeneracy between both effects is broken when Galactic foreground emission is used as a calibrator. In this work, we use realistic simulations of the High-Frequency Instrument of the
Planck
mission to test the impact that Galactic foreground emission and instrumental systematics have on the recent birefringence measurements obtained through this technique. Our results demonstrate the robustness of the methodology against the miscalibration of polarization angles and other systematic effects, like intensity-to-polarization leakage, beam leakage, or cross-polarization effects. However, our estimator is sensitive to the
EB
correlation of polarized foreground emission. Here we propose to correct the bias induced by dust
EB
by modeling the foreground signal with templates produced in Bayesian component-separation analyses that fit parametric models to CMB data. Acknowledging the limitations of currently available dust templates like that of the
Commander
sky model, high-precision CMB data and a characterization of dust beyond the modified blackbody paradigm are needed to obtain a definitive measurement of cosmic birefringence in the future.
Abstract
The new generation of CMB polarization experiments will reach limits of sensitivity never achieved before in order to detect the elusive primordial
B
-mode signal. However, all these efforts ...will be futile if we lack a tight control of systematics. Here, we focus on the systematic that arises from the uncertainty on the calibration of polarization angles. Miscalibrated polarization angles induce a mixing of
E
- and
B
-modes that obscures the primordial
B
-mode signal. We introduce an iterative angular power spectra maximum likelihood-based method to calculate the polarization angles (α̂) from the multi-frequency signal. The basis behind this methodology grounds on nulling the
C
ℓ
EB
power spectra. In order to simplify the likelihood, we assume that the rotation angles are small (≲ 6°) and, the maximum likelihood solution for the rotation angles α̂ is obtained by applying an iterative process where the covariance matrix does not depend on α̂ per iteration, i.e., the rotation angles are fixed to the estimated α̂ in the previous iteration. With these assumptions, we obtain an analytical linear system which leads to a very fast computational implementation. We show that with this methodology we are able to determine the rotation angle for each frequency with sufficiently good accuracy. To prove the latter point we perform component separation analyses using the parametric component separation method B-SeCRET with two different approaches. In the first approach we apply the B-SeCRET pipeline to the signal de-rotated with the estimation of α̂, while in the second, the rotation angles are treated as model parameters using the estimation of α̂ as a prior information. We obtain that the rotation angles estimations improve after applying the second approach, and show that the systematic residuals due to the non-null calibration polarization angles are mitigated to the order of a 1% at the power spectrum level.
Here, a methodology to provide the polarization angle requirements for different sets of detectors, at a given frequency of a CMB polarization experiment, is presented. The uncertainties in the ...polarization angle of each detector set are related to a given bias on the tensor-to-scalar ratio r parameter. The approach is grounded in using a linear combination of the detector sets to obtain the CMB polarization signal. In addition, assuming that the uncertainties on the polarization angle are in the small angle limit (lower than a few degrees), it is possible to derive analytic expressions to establish the requirements. The methodology also accounts for possible correlations among detectors, that may originate from the optics, wafers, etc. The approach is applied to the LiteBIRD space mission. We show that, for the most restrictive case (i.e., full correlation of the polarization angle systematics among detector sets), the requirements on the polarization angle uncertainties are of around 1 arcmin at the most sensitive frequency bands (i.e., ≈ 150 GHz) and of few tens of arcmin at the lowest (i.e., ≈ 40 GHz) and highest (i.e., ≈ 400 GHz) observational bands. Conversely, for the least restrictive case (i.e., no correlation of the polarization angle systematics among detector sets), the requirements are ≈ 5 times less restrictive than for the previous scenario. At the global and the telescope levels, polarization angle knowledge of a few arcmins is sufficient for correlated global systematic errors and can be relaxed by a factor of two for fully uncorrelated errors in detector polarization angle. The reported uncertainty levels are needed in order to have the bias on r due to systematics below the limit established by the LiteBIRD collaboration.
When coupled to electromagnetism via a Chern-Simons interaction, axion-like
particles (ALP) produce a rotation of the plane of linear polarization of
photons known as cosmic birefringence. Recent ...measurements of cosmic
birefringence obtained from the polarization of the cosmic microwave background
(CMB) hint at the existence of an isotropic birefringence angle of
$\beta\approx 0.3^\circ$, currently excluding $\beta=0$ with a statistical
significance of $3.6\sigma$. Were such measurement to be confirmed as a
cosmological signal, CMB information alone could constrain the ALP parameter
space for masses $m_\phi\lesssim 10^{-27}$eV and axion-photon coupling
constants $g_{\phi\gamma}\gtrsim 10^{-20}$GeV$^{-1}$.
Although interesting in themselves, extragalactic sources emitting in the microwave range (mainly radio-loud active galactic nuclei and dusty galaxies) are also considered a contaminant from the ...point of view of Cosmic Microwave Background (CMB) experiments. These sources appear as unresolved point-like objects in CMB measurements because of the limited resolution of CMB experiments. Amongst other issues, point-like sources are known to obstruct the reconstruction of the lensing potential, and can hinder the detection of the Primordial Gravitational Wave Background for low values of \(r\). Therefore, extragalactic point-source detection and subtraction is a fundamental part of the component separation process necessary to achieve some of the science goals set for the next generation of CMB experiments. As a previous step to their removal, in this work we present a new filter based on steerable wavelets that allows the characterization of the emission of these extragalactic sources. Instead of the usual approach of working in polarization maps of the Stokes' \(Q\) and \(U\) parameters, the proposed filter operates on E- and B-mode polarization maps. In this way, it benefits from the lower intensity that, both, the CMB, and the galactic foreground emission, present in B-modes to improve its performance. To demonstrate its potential, we have applied the filter to simulations of the future PICO satellite, and we predict that, for the regions of fainter galactic foreground emission in the 30 GHz and 155 GHz bands of PICO, our filter will be able to characterize sources down to a minimum polarization intensity of, respectively, 125 pK and 14 pK. Adopting a \(\Pi=0.02\) polarization degree, these values correspond to 169 mJy and 288 mJy intensities.
We propose a machine learning approach to the blind detection of extragalactic point sources on maps of the temperature anisotropies of the cosmic microwave background. Using realistic simulations of ...the microwave sky as seen by Planck, we train a convolutional neural network (CNN) that solves source detection as an image segmentation problem. We divide the sky into regions of progressively increasing Galactic foreground intensity and independently train specialized CNNs for each region. This strategy leads to promising levels of completeness and reliability, with our CNN substantially outperforming traditional detection methods like the matched filter in regions close to the Galactic plane.
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