Mathew Galloway

• Banday, A. J.; Gimeno-Amo, C.; Diego-Palazuelos, P.; Hoz, E. de la; Gruppuso, A. & Raffuzzi, N. [Show all 104 contributors for this article] (2026). LiteBIRD science goals and forecasts. E-mode anomalies. Journal of Cosmology and Astroparticle Physics (JCAP). 2026(1). doi: 10.1088/1475-7516/2026/01/036. Full text in Research Archive Show summary

  Various so-called anomalies have been found in both the WMAP and Planck cosmic microwave background (CMB) temperature data that exert a mild tension against the highly successful best-fit 6 parameter cosmological model, potentially providing hints of new physics to be explored. That these are real features on the sky is uncontested. However, given their modest significance, whether they are indicative of true departures from the standard cosmology or simply statistical excursions due to a mildly unusual configuration of temperature anisotropies on the sky which we refer to as the “fluke hypothesis” cannot be addressed further without new information. No theoretical model of primordial perturbations has to date been constructed that can explain all of the temperature anomalies. Therefore, we focus in this paper on testing the fluke hypothesis, based on the partial correlation between the temperature and E-mode CMB polarisation signal. In particular, we compare the properties of specific statistics in polarisation, built from unconstrained realisations of the ΛCDM cosmological model as might be observed by the LiteBIRD satellite, with those determined from constrained simulations, where the part of the E-mode anisotropy correlated with temperature is constrained by observations of the latter. Specifically, we use inpainted Planck 2018 SMICA temperature data to constrain the E-mode realisations. Subsequent analysis makes use of masks defined to minimise the impact of the inpainting procedure on the E-mode map statistics. We find that statistical assessments of the E-mode data alone do not provide any evidence for or against the fluke hypothesis. However, tests based on cross-statistical measures determined from temperature and E modes can allow this hypothesis to be rejected with a moderate level of probability.

• Ruiz-Granda, M.; Diego-Palazuelos, P.; Gimeno-Amo, C.; Vielva, P.; Lonappan, A.I. & Namikawa, T. [Show all 105 contributors for this article] (2025). LiteBIRD science goals and forecasts: improved full-sky reconstruction of the gravitational lensing potential through the combination of Planck and LiteBIRD data. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(11). doi: 10.1088/1475-7516/2025/11/073. Full text in Research Archive Show summary

  Cosmic microwave background (CMB) photons are deflected by large-scale structure through gravitational lensing. This secondary effect introduces higher-order correlations in CMB anisotropies, which are used to reconstruct lensing deflections. This allows mapping of the integrated matter distribution along the line of sight, probing the growth of structure, and recovering an undistorted view of the last-scattering surface. Gravitational lensing has been measured by previous CMB experiments, with Planck 's 42 σ detection being the current best full-sky lensing map. We present an enhanced LiteBIRD lensing map by extending the CMB multipole range and including the minimum-variance estimation, leading to a 49 to 58 σ detection over 80 % of the sky, depending on the final complexity of polarized Galactic emission. The combination of Planck and LiteBIRD will be the best full-sky lensing map in the 2030s, providing a 72 to 78 σ detection over 80 % of the sky, almost doubling Planck 's sensitivity. Finally, we explore different applications of the lensing map, including cosmological parameter estimation using a lensing-only likelihood and internal delensing, showing that the combination of both experiments leads to improved constraints. The combination of Planck + LiteBIRD will improve the S 8 constraint by a factor of 2 compared to Planck , and Planck + LiteBIRD internal delensing will improve LiteBIRD 's tensor-to-scalar ratio constraint by 6 %. We have tested the robustness of our results against foreground models of different complexity, showing that improvements remain even for the most complex foregrounds.

• Bortolami, M.; Raffuzzi, N.; Pagano, L.; Puglisi, G.; Anand, A. & Banday, A.J. [Show all 110 contributors for this article] (2025). First release of LiteBIRD simulations from an end-to-end pipeline. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(11). doi: 10.1088/1475-7516/2025/11/042. Full text in Research Archive Show summary

  The LiteBIRD satellite mission aims at detecting Cosmic Microwave Background B modes with unprecedented precision, targeting a total error on the tensor-to-scalar ratio r of δr ∼ 0.001. Operating from the L2 Lagrangian point of the Sun-Earth system, LiteBIRD will survey the full sky across 15 frequency bands (34 to 448 GHz) for 3 years.The current LiteBIRD baseline configuration employs 4508 detectors sampling at 19.1 Hz to achieve an effective polarization sensitivity of 2 μK arcmin and an angular resolution of 31 arcmin (at 140 GHz). We describe the first release of the official LiteBIRD simulations, realized with a new simulation pipeline developed using the LiteBIRD Simulation Framework. This pipeline generates 500 full-sky simulated maps at a HEALPix resolution of Nside=512. The simulations include also one year of Time Ordered Data (TOD) for approximately one-third of LiteBIRD's total detectors.

• Aurvik, Ragnhild; Galloway, Mathew; Gjerløw, Eirik; Fuskeland, Unni; Basyrov, Artem & Bortolami, M. [Show all 110 contributors for this article] (2025). On the computational feasibility of Bayesian end-to-end analysis of LiteBIRD simulations within Cosmoglobe. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(11). doi: 10.1088/1475-7516/2025/11/041. Full text in Research Archive Show summary

  We assess the computational feasibility of end-to-end Bayesian analysis of the JAXA-led LiteBIRD experiment by analysing simulated time ordered data (TOD) for a subset of detectors through the Cosmoglobe and Commander3 framework. The data volume for the simulated TOD is 1.55 TB, or 470 GB after Huffman compression. From this we estimate a total data volume of 238 TB for the full three year mission, or 70 TB after Huffman compression. We further estimate the running time for one Gibbs sample, from TOD to cosmological parameters, to be approximately 3000 CPU hours. The current simulations are based on an ideal instrument model, only including correlated 1/ f noise. Future work will consider realistic systematics with full end-to-end error propagation. We conclude that these requirements are well within capabilities of future high-performance computing systems.

• Tomasi, M.; Pagano, L.; Anand, A.; Baccigalupi, C.; Banday, A.J. & Bortolami, M. [Show all 114 contributors for this article] (2025). A simulation framework for the LiteBIRD instruments. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(11). doi: 10.1088/1475-7516/2025/11/040. Full text in Research Archive Show summary

  LiteBIRD , the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission focused on primordial cosmology and fundamental physics. In this paper, we present the LiteBIRD Simulation Framework (LBS), a Python package designed for the implementation of pipelines that model the outputs of the data acquisition process from the three instruments on the LiteBIRD spacecraft: LFT (Low-Frequency Telescope), MFT (Mid-Frequency Telescope), and HFT (High-Frequency Telescope). LBS provides several modules to simulate the scanning strategy of the telescopes, the measurement of realistic polarized radiation coming from the sky (including the Cosmic Microwave Background itself, the Solar and Kinematic dipole, and the diffuse foregrounds emitted by the Galaxy), the generation of instrumental noise and the effect of systematic errors, like pointing wobbling, non-idealities in the Half-Wave Plate, et cetera . Additionally, we present the implementation of a simple but complete pipeline that showcases the main features of LBS. We also discuss how we ensured that LBS lets people develop pipelines whose results are accurate and reproducible. A full end-to-end pipeline has been developed using LBS to characterize the scientific performance of the LiteBIRD experiment. This pipeline and the results of the first simulation run are presented in Puglisi et al. (2025).

• Giardiello, S.; Carones, A.; Ghigna, T.; Pagano, L.; Piacentini, F. & Montier, L. [Show all 98 contributors for this article] (2025). Requirements on bandpass resolution and measurement precision for LiteBIRD. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(10). doi: 10.1088/1475-7516/2025/10/038. Full text in Research Archive Show summary

  Systematic effects can hinder the sought-after detection of primordial gravitational waves, impacting the reconstruction of the B -mode polarization signal which they generate in the cosmic microwave background (CMB). In this work, we study the impact of an imperfect knowledge of the instrument bandpasses on the estimate of the tensor-to-scalar ratio r in the context of the next-generation LiteBIRD satellite. We develop a pipeline to integrate over the bandpass transmission in both the time-ordered data (TOD) and the map-making processing steps. We introduce the systematic effect by having a mismatch between the “real”, high resolution bandpass τ , entering the TOD, and the estimated one τ s , used in the map-making. We focus on two aspects: the effect of degrading the τ s resolution, and the addition of a Gaussian error σ to τ s . To reduce the computational load of the analysis, the two effects are explored separately, for three representative LiteBIRD channels (40 GHz, 140 GHz and 402 GHz) and for three bandpass shapes. Computing the amount of bias on r , Δ r , caused by these effects on a single channel, we find that a resolution ≲ 1.5 GHz and σ ≲ 0.0089 do not exceed the LiteBIRD budget allocation per systematic effect, Δ r < 6.5 × 10 -6 . We then check that propagating separately the uncertainties due to a resolution of 1 GHz and a measurement error with σ = 0.0089 in all LiteBIRD frequency channels, for the most pessimistic bandpass shape of the three considered, still produces a Δ r < 6.5 × 10 -6 . This is done both with the simple deprojection approach and with a blind component separation technique, the Needlet Internal Linear Combination (NILC). Due to the effectiveness of NILC in cleaning the systematic residuals, we have tested that the requirement on σ can be relaxed to σ ≲ 0.05.

• Carralot, F.; Carones, A.; Krachmalnicoff, N.; Ghigna, T.; Novelli, A. & Pagano, L. [Show all 109 contributors for this article] (2025). Requirements on the gain calibration for LiteBIRD polarisation data with blind component separation. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(1). doi: 10.1088/1475-7516/2025/01/019. Full text in Research Archive Show summary

  The detection of primordial B modes of the cosmic microwave background (CMB) could provide information about the early stages of the Universe's evolution. The faintness of this signal requires exquisite calibration accuracy and control of instrumental systematic effects which otherwise could bias the measurements. In this work, we study the impact of an imperfect relative polarisation gain calibration on the recovered value of the tensor-to-scalar ratio r for the LiteBIRD experiment, through the application of the blind Needlet Internal Linear Combination (NILC) foreground-cleaning method. We derive requirements on the relative calibration accuracy of the overall polarisation gain (Δgν) for each LiteBIRD frequency channel. Our results show that minimum variance techniques, as NILC, are less sensitive to systematic gain calibration uncertainties compared to a parametric approach, if the latter is not equipped with a proper modelling of these instrumental effects. In this study, the most stringent requirements are found in the channels where the CMB signal is relatively brighter, with the tightest constraints at 166 GHz (Δgν ≈ 0.16%). This differs from the outcome of an analogous analysis performed with a parametric method, where the tightest requirements are obtained for the foreground-dominated channels. Gain calibration uncertainties, corresponding to the derived requirements, are then simultaneously propagated into all frequency channels. By doing so, we find that the overall impact on estimated r is lower than the total gain systematic budget for LiteBIRD approximately by a factor 5, due to the correlations of the impacts of gain calibration uncertainties in different frequency channels. In order to decouple the systematic effect from the specific choice of the model, we derive the requirements assuming constant spectral parameters for the foreground emission. To assess the robustness of the obtained results against more realistic scenarios, we repeat the analysis assuming sky models of intermediate and high complexity. In these further cases, we adopt an optimised NILC pipeline, called the Multi-Clustering NILC (MC-NILC). We find that the impact of gain calibration uncertainties on r is lower than the LiteBIRD gain systematics budget for the intermediate-complexity sky model. For the high-complexity case, instead, it would be necessary to tighten the requirements by a factor 1.8.

• Hoz, E. de la; Diego-Palazuelos, P.; Errard, J.; Gruppuso, A.; Jost, B. & Sullivan, Raelyn [Show all 115 contributors for this article] (2025). LiteBIRD science goals and forecasts: constraining isotropic cosmic birefringence. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(7). doi: 10.1088/1475-7516/2025/07/083. Full text in Research Archive Show summary

  Cosmic birefringence (CB) is the rotation of the photons' linear polarisation plane during propagation. Such an effect is a tracer of parity-violating extensions of standard electromagnetism and would probe the existence of a new cosmological field acting as dark matter or dark energy. It has become customary to employ cosmic microwave background (CMB) polarised data to probe such a phenomenon. Recent analyses on Planck and WMAP data provide a hint of detection of the isotropic CB angle with an amplitude of around 0.3° at the level of 2.4 to 3.6σ. In this work, we explore the LiteBIRD capabilities in constraining such an effect, accounting for the impact of the more relevant systematic effects, namely foreground emission and instrumental polarisation angles. We build five semi-independent pipelines and test these against four different simulation sets with increasing complexity in terms of non-idealities. All the pipelines are shown to be robust and capable of returning the expected values of the CB angle within statistical fluctuations for all the cases considered. We find that the uncertainties in the CB estimates increase with more complex simulations. However, the trend is less pronounced for pipelines that account for the instrumental polarisation angles. For the most complex case analysed, we find that LiteBIRD will be able to detect a CB angle of 0.3° with a statistical significance ranging from 5 to 13σ, depending on the pipeline employed, where the latter uncertainty corresponds to a total error budget of the order of 0.02°.

• Ade, P.A.R.; Amiri, M.; Benton, S.J.; Bergman, A.S.; Bihary, R. & Bock, J.J. [Show all 69 contributors for this article] (2025). Analysis of Polarized Dust Emission Using Data from the First Flight of SPIDER. The Astrophysical Journal (ApJ). ISSN 0004-637X. 978(2). doi: 10.3847/1538-4357/ad900c. Full text in Research Archive Show summary

  Using data from the first flight of Spider and from the Planck High Frequency Instrument, we probe the properties of polarized emission from interstellar dust in the Spider observing region. Component-separation algorithms operating in both the spatial and harmonic domains are applied to probe their consistency and to quantify modeling errors associated with their assumptions. Analyses of diffuse Galactic dust emission spanning the full Spider region demonstrate (i) a spectral energy distribution that is broadly consistent with a modified-blackbody (MBB) model with a spectral index of βd = 1.45 ± 0.05 (1.47 ± 0.06) for E (B)-mode polarization, slightly lower than that reported by Planck for the full sky; (ii) an angular power spectrum broadly consistent with a power law; and (iii) no significant detection of line-of-sight polarization decorrelation. Tests of several modeling uncertainties find only a modest impact (∼10% in σr) on Spider's sensitivity to the cosmological tensor-to-scalar ratio. The size of the Spider region further allows for a statistically meaningful analysis of the variation in foreground properties within it. Assuming a fixed dust temperature Td = 19.6 K, an analysis of two independent subregions of that field results in inferred values of βd = 1.52 ± 0.06 and βd = 1.09 ± 0.09, which are inconsistent at the 3.9σ level. Furthermore, a joint analysis of Spider and Planck 217 and 353 GHz data within one subregion is inconsistent with a simple MBB at more than 3σ, assuming a common morphology of polarized dust emission over the full range of frequencies. This evidence of variation may inform the component-separation approaches of future cosmic microwave background polarization experiments.

• Remazeilles, M.; Douspis, M.; Rubiño-Martín, J.A.; Banday, A.J.; Chluba, J. & Bernardis, P. de [Show all 107 contributors for this article] (2024). LiteBIRD science goals and forecasts. Mapping the hot gas in the Universe. Journal of Cosmology and Astroparticle Physics (JCAP). 2024(12). doi: 10.1088/1475-7516/2024/12/026. Full text in Research Archive Show summary

  We assess the capabilities of the LiteBIRD mission to map the hot gas distribution in the Universe through the thermal Sunyaev-Zeldovich (SZ) effect. Our analysis relies on comprehensive simulations incorporating various sources of Galactic and extragalactic foreground emission, while accounting for the specific instrumental characteristics of the LiteBIRDmission, such as detector sensitivities, frequency-dependent beam convolution, inhomogeneous sky scanning, and 1/f noise. We implement a tailored component-separation pipeline to map the thermal SZ Compton y-parameter over 98% of the sky. Despite lower angular resolution for galaxy cluster science, LiteBIRD provides full-sky coverage and, compared to the Plancksatellite, enhanced sensitivity, as well as more frequency bands to enable the construction of an all-sky thermal SZ y-map, with reduced foreground contamination at large and intermediate angular scales. By combining LiteBIRD and Planck channels in the component-separation pipeline, we also obtain an optimal y-map that leverages the advantages of both experiments, with the higher angular resolution of the Planck channels enabling the recovery of compact clusters beyond the LiteBIRD beam limitations, and the numerous sensitive LiteBIRD channels further mitigating foregrounds. The added value ofLiteBIRD is highlighted through the examination of maps, power spectra, and one-point statistics of the various sky components. After component separation, the 1/f noise fromLiteBIRD's intensity channels is effectively mitigated below the level of the thermal SZ signal at all multipoles. Cosmological constraints on S8 = σ8 (Ωm/0.3)0.5 obtained from the LiteBIRD-Planck combined y-map power spectrum exhibits a 15 % reduction in uncertainty compared to constraints derived fromPlanck alone. This improvement can be attributed to the increased portion of uncontaminated sky available in the LiteBIRD-Planck combined y-map.

• Ghigna, T.; Adler, A.; Aizawa, K.; Akamutsu, H.; Akizawa, R. & Allys, E. [Show all 157 contributors for this article] (2024). The LiteBIRD mission to explore cosmic inflation. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 13092. doi: 10.1117/12.3021377. Full text in Research Archive Show summary

  LiteBIRD, the next-generation cosmic microwave background (CMB) experiment, aims for a launch in Japan’s fiscal year 2032, marking a major advancement in the exploration of primordial cosmology and fundamental physics. Orbiting the Sun-Earth Lagrangian point L2, this JAXA-led strategic L-class mission will conduct a comprehensive mapping of the CMB polarization across the entire sky. During its 3-year mission, LiteBIRD will employ three telescopes within 15 unique frequency bands (ranging from 34 through 448 GHz), targeting a sensitivity of 2.2 μK-arcmin and a resolution of 0.5° at 100 GHz. Its primary goal is to measure the tensor-toscalar ratio r with an uncertainty δr = 0.001, including systematic errors and margin. If r ≥ 0.01, LiteBIRD expects to achieve a > 5σ detection in the ℓ = 2–10 and ℓ = 11–200 ranges separately, providing crucial insight into the early Universe. We describe LiteBIRD’s scientific objectives, the application of systems engineering to mission requirements, the anticipated scientific impact, and the operations and scanning strategies vital to minimizing systematic effects. We will also highlight LiteBIRD’s synergies with concurrent CMB projects.

• Paoletti, D.; Rubino-Martin, J.A.; Shiraishi, M.; Molinari, D.; Chluba, J. & Finelli, F. [Show all 100 contributors for this article] (2024). LiteBIRD science goals and forecasts: primordial magnetic fields. Journal of Cosmology and Astroparticle Physics (JCAP). 2024(7). doi: 10.1088/1475-7516/2024/07/086. Full text in Research Archive Show summary

  We present detailed forecasts for the constraints on the characteristics of primordial magnetic fields (PMFs) generated prior to recombination that will be obtained with the LiteBIRD satellite. The constraints are driven by some of the main physical effects of PMFs on the CMB anisotropies: the gravitational effects of magnetically-induced perturbations; the effects on the thermal and ionization history of the Universe; the Faraday rotation imprint on the CMB polarization spectra; and the non-Gaussianities induced in polarization anisotropies. LiteBIRD represents a sensitive probe for PMFs. We explore different levels of complexity, for LiteBIRD data and PMF configurations, accounting for possible degeneracies with primordial gravitational waves from inflation. By exploiting all the physical effects, LiteBIRD will be able to improve the current limit on PMFs at intermediate and large scales coming from Planck. In particular, thanks to its accurate B-mode polarization measurement, LiteBIRD will improve the constraints on infrared configurations for the gravitational effect, giving BnB=-2.91 Mpc< 0.8 nG at 95% C.L., potentially opening the possibility to detect nanogauss fields with high significance. We also observe a significant improvement in the limits when marginalized over the spectral index, BnBmarg1 Mpc< 2.2 nG at 95 % C.L. From the thermal history effect, which relies mainly on E-mode polarization data, we obtain a significant improvement for all PMF configurations, with the marginalized case, √⟨B2⟩marg<0.50 nG at 95 % C.L. Faraday rotation constraints will take advantage of the wide frequency coverage of LiteBIRD and the high sensitivity in B modes, improving the limits by orders of magnitude with respect to current results, BnB=-2.91 Mpc < 3.2 nG at 95 % C.L. Finally, non-Gaussianities of the B-mode polarization can probe PMFs at the level of 1 nG, again significantly improving the current bounds from Planck. Altogether our forecasts represent a broad collection of complementary probes based on widely tested methodologies, providing conservative limits on PMF characteristics that will be achieved with the LiteBIRD satellite.

• Takase, Y.; Vacher, L.; Ishino, H.; Patanchon, G.; Montier, L. & Stever, S.L. [Show all 108 contributors for this article] (2024). Multi-dimensional optimisation of the scanning strategy for the LiteBIRD space mission. Journal of Cosmology and Astroparticle Physics (JCAP). 2024(12). doi: 10.1088/1475-7516/2024/12/036. Full text in Research Archive Show summary

  Large angular scale surveys in the absence of atmosphere are essential for measuring the primordial B-mode power spectrum of the Cosmic Microwave Background (CMB). Since this proposed measurement is about three to four orders of magnitude fainter than the temperature anisotropies of the CMB, in-flight calibration of the instruments and active suppression of systematic effects are crucial. We investigate the effect of changing the parameters of the scanning strategy on the in-flight calibration effectiveness, the suppression of the systematic effects themselves, and the ability to distinguish systematic effects by null-tests. Next-generation missions such as LiteBIRD, modulated by a Half-Wave Plate (HWP), will be able to observe polarisation using a single detector, eliminating the need to combine several detectors to measure polarisation, as done in many previous experiments and hence avoiding the consequent systematic effects. While the HWP is expected to suppress many systematic effects, some of them will remain. We use an analytical approach to comprehensively address the mitigation of these systematic effects and identify the characteristics of scanning strategies that are the most effective for implementing a variety of calibration strategies in the multi-dimensional space of common spacecraft scan parameters. We verify that LiteBIRD's standard configuration yields good performance on the metrics we studied. We also present Falcons.jl, a fast spacecraft scanning simulator that we developed to investigate this scanning parameter space.

• Campeti, P.; Komatsu, E.; Baccigalupi, C.; Ballardini, M.; Bartolo, N. & Carones, A. [Show all 110 contributors for this article] (2024). LiteBIRD science goals and forecasts. A case study of the origin of primordial gravitational waves using large-scale CMB polarization. Journal of Cosmology and Astroparticle Physics (JCAP). 2024(6). doi: 10.1088/1475-7516/2024/06/008. Full text in Research Archive Show summary

  We study the possibility of using the LiteBIRD satellite B-mode survey to constrain models of inflation producing specific features in CMB angular power spectra. We explore a particular model example, i.e. spectator axion-SU(2) gauge field inflation. This model can source parity-violating gravitational waves from the amplification of gauge field fluctuations driven by a pseudoscalar "axionlike" field, rolling for a few e-folds during inflation. The sourced gravitational waves can exceed the vacuum contribution at reionization bump scales by about an order of magnitude and can be comparable to the vacuum contribution at recombination bump scales. We argue that a satellite mission with full sky coverage and access to the reionization bump scales is necessary to understand the origin of the primordial gravitational wave signal and distinguish among two production mechanisms: quantum vacuum fluctuations of spacetime and matter sources during inflation. We present the expected constraints on model parameters from LiteBIRD satellite simulations, which complement and expand previous studies in the literature. We find that LiteBIRD will be able to exclude with high significance standard single-field slow-roll models, such as the Starobinsky model, if the true model is the axion-SU(2) model with a feature at CMB scales. We further investigate the possibility of using the parity-violating signature of the model, such as the TB and EB angular power spectra, to disentangle it from the standard single-field slow-roll scenario. We find that most of the discriminating power of LiteBIRD will reside in BB angular power spectra rather than in TB and EB correlations.

• Leloup, C.; Patanchon, G.; Errard, J.; Franceschet, C.; Gudmundsson, J.E. & Henrot-Versillé, S. [Show all 112 contributors for this article] (2024). Impact of beam far side-lobe knowledge in the presence of foregrounds for LiteBIRD. Journal of Cosmology and Astroparticle Physics (JCAP). 2024(6). doi: 10.1088/1475-7516/2024/06/01. Full text in Research Archive Show summary

  We present a study of the impact of a beam far side-lobe lack of knowledge on the measurement of the Cosmic Microwave Background B-mode signal at large scale. Beam far side-lobes induce a mismatch in the transfer function of Galactic foregrounds between the dipole and higher multipoles which degrads the performances of component separation methods. This leads to foreground residuals in the CMB map. It is expected to be one of the main source of systematic effects in future CMB polarization observations. Thus, it becomes crucial for all-sky survey missions to take into account the interplays between beam systematic effects and all the data analysis steps. LiteBIRD is the ISAS/JAXA second strategic large-class satellite mission and is dedicated to target the measurement of CMB primordial B modes by reaching a sensitivity on the tensor-to-scalar ratio r of σ(r) ≤ 10-3 assuming r = 0. The primary goal of this paper is to provide the methodology and develop the framework to carry out the end-to-end study of beam far side-lobe effects for a space-borne CMB experiment. We introduce uncertainties in the beam model, and propagate the beam effects through all the steps of the analysis pipeline, most importantly including component separation, up to the cosmological results in the form of a bias δr. As a demonstration of our framework, we derive requirements on the calibration and modeling for the LiteBIRD's beams under given assumptions on design, simulation, component separation method and allocated error budget. In particular, we assume a parametric method of component separation with no mitigation of the far side-lobes effect at any stage of the analysis pipeline. We show that δr is mostly due to the integrated fractional power difference between the estimated beams and the true beams in the far side-lobes region, with little dependence on the actual shape of the beams, for low enough δr. Under our set of assumptions, in particular considering the specific foreground cleaning method we used, we find that the integrated fractional power in the far side-lobes should be known at the level of ∼ 10-4, to achieve the required limit on the bias δr < 1.9 × 10-5. The framework and tools developed for this study can be easily adapted to provide requirements under different design, data analysis frameworks and for other future space-borne experiments, such as PICO or CMB-Bharat. We further discuss the limitations of this framework and potential extensions to circumvent them.

• Shaw, Elle C.; Ade, Peter A. R.; Akers, Scott; Amiri, Mandana; Austermann, Jason & Beall, James [Show all 86 contributors for this article] (2024). In-flight performance of Spider's 280-GHz receivers. Journal of Astronomical Telescopes, Instruments, and Systems (JATIS). ISSN 2329-4124. 10(4). doi: 10.1117/1.JATIS.10.4.044012. Full text in Research Archive Show summary

  Spider is a balloon-borne instrument designed to map the cosmic microwave background at degree-angular scales in the presence of Galactic foregrounds. Spider has mapped a large sky area in the Southern Hemisphere using more than 2000 transition-edge sensors (TESs) during two NASA Long Duration Balloon flights above the Antarctic continent. During its first flight in January 2015, Spider was observed in the 95- and 150-GHz frequency bands, setting constraints on the B-mode signature of primordial gravitational waves. Its second flight in the 2022–2023 season added new receivers at 280 GHz, each using an array of TESs coupled to the sky through feedhorns formed from stacks of silicon wafers. These receivers are optimized to produce deep maps of polarized Galactic dust emission over a large sky area, providing a unique data set with lasting value to the field. We describe the instrument’s performance during Spider’s second flight, focusing on the performance of the 280-GHz receivers. We include details on the flight, in-band optical loading at float, and an early analysis of detector noise.

• Shaw, E.C.; Ade, P.A.R.; Akers, S.; Amiri, M.; Austermann, J. & Beall, J. [Show all 87 contributors for this article] (2024). In-flight performance of SPIDER's 280 GHz receivers. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 13102. doi: 10.1117/12.3016837. Full text in Research Archive Show summary

  SPIDER is a balloon-borne instrument designed to map the cosmic microwave background at degree-angular scales in the presence of Galactic foregrounds. Spider has mapped a large sky area in the Southern Hemisphere using more than 2000 transition-edge sensors (TESs) during two NASA Long Duration Balloon flights above the Antarctic continent. During its first flight in January 2015, Spider observed in the 95 GHz and 150 GHz frequency bands, setting constraints on the B-mode signature of primordial gravitational waves. Its second flight in the 2022-23 season added new receivers at 280 GHz, each using an array of TESs coupled to the sky through feedhorns formed from stacks of silicon wafers. These receivers are optimized to produce deep maps of polarized Galactic dust emission over a large sky area, providing a unique data set with lasting value to the field. In this work, we describe the instrument’s performance during SPIDER’s second flight.

• Lonappan, A.I.; Namikawa, T.; Piccirilli, G.; Diego-Palazuelos, P.; Ruiz-Granda, M. & Migliaccio, M. [Show all 122 contributors for this article] (2024). LiteBIRD science goals and forecasts: a full-sky measurement of gravitational lensing of the CMB. Journal of Cosmology and Astroparticle Physics (JCAP). 2024(6). doi: 10.1088/1475-7516/2024/06/009. Full text in Research Archive Show summary

  We explore the capability of measuring lensing signals in LiteBIRD full-sky polarization maps. With a 30 arcmin beam width and an impressively low polarization noise of 2.16 μK-arcmin,LiteBIRD will be able to measure the full-sky polarization of the cosmic microwave background (CMB) very precisely. This unique sensitivity also enables the reconstruction of a nearly full-sky lensing map using only polarization data, even considering its limited capability to capture small-scale CMB anisotropies. In this paper, we investigate the ability to construct a full-sky lensing measurement in the presence of Galactic foregrounds, finding that several possible biases from Galactic foregrounds should be negligible after component separation by harmonic-space internal linear combination. We find that the signal-to-noise ratio of the lensing is approximately 40 using only polarization data measured over 80% of the sky. This achievement is comparable to Planck's recent lensing measurement with both temperature and polarization and represents a four-fold improvement over Planck's polarization-only lensing measurement. The LiteBIRD lensing map will complement the Planck lensing map and provide several opportunities for cross-correlation science, especially in the northern hemisphere.

• Watts, Duncan; Fuskeland, Unni; Aurvik, Ragnhild; Basyrov, Artem; Bianchi, L.A. & Brilenkov, Maksym [Show all 21 contributors for this article] (2024). COSMOGLOBE DR1 results: III. First full-sky model of polarized synchrotron emission from all WMAP and Planck LFI data. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 686. doi: 10.1051/0004-6361/202348330. Full text in Research Archive Show summary

  We present the first model of full-sky polarized synchrotron emission that is derived from all WMAP and Planck LFI frequency maps. The basis of this analysis is the set of end-to-end reprocessed COSMOGLOBE Data Release 1 (DR1) sky maps presented in a companion paper, which have significantly lower instrumental systematics than the legacy products from each experiment. We find that the resulting polarized synchrotron amplitude map has an average noise rms per 2° full width at half maximum (FWHM) beam of 3.2 μK at 30 GHz. This is 30% lower than the recently released BEYONDPLANCK model that included only LFI+WMAP Ka–V data, and 29% lower than the WMAP K-band map alone. The mean B-to-E power spectrum ratio is 0.39 ± 0.02, with amplitudes consistent with those measured previously by Planck and QUIJOTE. Assuming a power law model for the synchrotron spectral energy distribution and using the T–T plot method, we find a full-sky inverse noise-variance-weighted mean of the synchrotron polarized spectral index of βs = −3.07 ± 0.07 from the COSMOGLOBE DR1 K band and 30 GHz, in good agreement with previous estimates. In summary, the novel COSMOGLOBE DR1 synchrotron model is both more sensitive and systematically cleaner than similar previous models, and it has a more complete error description that is defined by a set of Monte Carlo posterior samples. We believe that these products are preferable over previous Planck and WMAP products for all synchrotron-related scientific applications, including simulations, forecasting, and component separation.

• Namikawa, T.; Lonappan, A.; Baccigalupi, C.; Bartolo, N.; Beck, D. & Benabed, K. [Show all 122 contributors for this article] (2024). LiteBIRD science goals and forecasts: improving sensitivity to inflationary gravitational waves with multitracer delensing. Journal of Cosmology and Astroparticle Physics (JCAP). 2024(6). doi: 10.1088/1475-7516/2024/06/010. Full text in Research Archive Show summary

  We estimate the efficiency of mitigating the lensing B-mode polarization, the so-called delensing, for the LiteBIRD experiment with multiple external data sets of lensing-mass tracers. The current best bound on the tensor-to-scalar ratio, r, is limited by lensing rather than Galactic foregrounds. Delensing will be a critical step to improve sensitivity to r as measurements of r become more and more limited by lensing. In this paper, we extend the analysis of the recent LiteBIRD forecast paper to include multiple mass tracers, i.e., the CMB lensing maps from LiteBIRD and CMB-S4-like experiment, cosmic infrared background, and galaxy number density from Euclid- and LSST-like survey. We find that multi-tracer delensing will further improve the constraint on r by about 20%. In LiteBIRD, the residual Galactic foregrounds also significantly contribute to uncertainties of the B-modes, and delensing becomes more important if the residual foregrounds are further reduced by an improved component separation method.

• Eskilt, Johannes Røsok; Watts, Duncan; Aurvik, Ragnhild; Basyrov, Artem; Bersanelli, Marco & Brilenkov, Maksym [Show all 31 contributors for this article] (2023). Cosmoglobe DR1 results II. Constraints on isotropic cosmic birefringence from reprocessed WMAP and Planck LFI data. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 679. doi: 10.1051/0004-6361/202346829. Full text in Research Archive Show summary

  Cosmic birefringence is a parity-violating effect that might have rotated the plane of the linearly polarized light of the cosmic microwave background (CMB) by an angle β since its emission. This angle has recently been measured to be nonzero at a statistical significance of 3.6 σ in the official Planck PR4 and 9-year WMAP data. In this work, we constrain β using the reprocessed B EYOND P LANCK LFI and C OSMOGLOBE DR1 WMAP polarization maps. These novel maps have both lower systematic residuals and a more complete error description than the corresponding official products. Foreground EB correlations could bias measurements of β , and while thermal dust EB emission has been argued to be statistically nonzero, no evidence for synchrotron EB power has been reported. Unlike the dust-dominated Planck HFI maps, the majority of the LFI and WMAP polarization maps are instead dominated by synchrotron emission. Simultaneously constraining β and the polarization miscalibration angle, α , of each channel, we find a best-fit value of β  = 0.35° ±0.70° with LFI and WMAP data only. When including the Planck HFI PR4 maps, but fitting β separately for dust-dominated, β &gt; 70 GHz , and synchrotron-dominated channels, β ≤70 GHz , we find β ≤70 GHz  = 0.53° ±0.28°. This differs from zero with a statistical significance of 1.9 σ , and the main contribution to this value comes from the LFI 70 GHz channel. While the statistical significances of these results are low on their own, the measurement derived from the LFI and WMAP synchrotron-dominated maps agrees with the previously reported HFI-dominated constraints, despite the very different astrophysical and instrumental systematics involved in all these experiments.

• Brilenkov, Maksym; Fornazier, K.S.F.; Hergt, L.T.; Hoerning, G.A.; Marins, A. & Murokoshi, T. [Show all 51 contributors for this article] (2023). BeyondPlanck: IV. Simulations and validation. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202244958. Full text in Research Archive Show summary

  End-to-end simulations play a key role in the analysis of any high-sensitivity cosmic microwave background (CMB) experiment, providing high-fidelity systematic error propagation capabilities that are unmatched by any other means. In this paper, we address an important issue regarding such simulations, namely, how to define the inputs in terms of sky model and instrument parameters. These may either be taken as a constrained realization derived from the data or as a random realization independent from the data. We refer to these as posterior and prior simulations, respectively. We show that the two options lead to significantly different correlation structures, as prior simulations (contrary to posterior simulations) effectively include cosmic variance, but they exclude realization-specific correlations from non-linear degeneracies. Consequently, they quantify fundamentally different types of uncertainties. We argue that as a result, they also have different and complementary scientific uses, even if this dichotomy is not absolute. In particular, posterior simulations are in general more convenient for parameter estimation studies, while prior simulations are generally more convenient for model testing. Before B EYOND P LANCK , most pipelines used a mix of constrained and random inputs and applied the same hybrid simulations for all applications, even though the statistical justification for this is not always evident. B EYOND P LANCK represents the first end-to-end CMB simulation framework that is able to generate both types of simulations and these new capabilities have brought this topic to the forefront. The B EYOND P LANCK posterior simulations and their uses are described extensively in a suite of companion papers. In this work, we consider one important applications of the corresponding prior simulations, namely, code validation. Specifically, we generated a set of one-year LFI 30 GHz prior simulations with known inputs and we used these to validate the core low-level B EYOND P LANCK algorithms dealing with gain estimation, correlated noise estimation, and mapmaking.

• Aurvik, Ragnhild; Remazeilles, Mathieu; Belkner, Sebastian; Carron, Julien; Delabrouille, Jacques & Eriksen, Hans Kristian Kamfjord [Show all 17 contributors for this article] (2023). Foreground separation and constraints on primordial gravitational waves with the PICO space mission. Journal of Cosmology and Astroparticle Physics (JCAP). 2023(6). doi: 10.1088/1475-7516/2023/06/034. Full text in Research Archive Show summary

  PICO is a concept for a NASA probe-scale mission aiming to detect or constrain the tensor to scalar ratio r, a parameter that quantifies the amplitude of inflationary gravity waves. We carry out map-based component separation on simulations with five foreground models and input r values rin = 0 and rin = 0.003. We forecast r determinations using a Gaussian likelihood assuming either no delensing or a residual lensing factor Alens = 27%. By implementing the first full-sky, post component-separation, map-domain delensing, we show that PICO should be able to achieve Alens = 22% – 24%. For four of the five foreground models we find that PICO would be able to set the constraints r < 1.3 × 10-4 to r < 2.7 × 10-4 (95%) if rin = 0, the strongest constraints of any foreseeable instrument. For these models, r = 0.003 is recovered with confidence levels between 18σ and 27σ. We find weaker, and in some cases significantly biased, upper limits when removing few low or high frequency bands. The fifth model gives a 3σ detection when rin = 0 and a 3σ bias with rin = 0.003. However, by correlating r determinations from many small 2.5% sky areas with the mission's 555 GHz data we identify and mitigate the bias. This analysis underscores the importance of large sky coverage. We show that when only low multipoles ℓ ≤ 12 are used, the non-Gaussian shape of the true likelihood gives uncertainties that are on average 30% larger than a Gaussian approximation.

• Fuskeland, Unni; Aumont, J.; Aurvik, Ragnhild; Baccigalupi, C.; Banday, A.J. & Eriksen, Hans Kristian Kamfjord [Show all 117 contributors for this article] (2023). Tensor-to-scalar ratio forecasts for extended LiteBIRD frequency configurations. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 676. doi: 10.1051/0004-6361/202346155. Full text in Research Archive Show summary

  LiteBIRD is a planned JAXA-led cosmic microwave background (CMB) B -mode satellite experiment aiming for launch in the late 2020s, with a primary goal of detecting the imprint of primordial inflationary gravitational waves. Its current baseline focal-plane configuration includes 15 frequency bands between 40 and 402 GHz, fulfilling the mission requirements to detect the amplitude of gravitational waves with the total uncertainty on the tensor-to-scalar ratio, δr , down to δr  &lt; 0.001. A key aspect of this performance is accurate astrophysical component separation, and the ability to remove polarized thermal dust emission is particularly important. In this paper we note that the CMB frequency spectrum falls off nearly exponentially above 300 GHz relative to the thermal dust spectral energy distribution, and a relatively minor high frequency extension can therefore result in even lower uncertainties and better model reconstructions. Specifically, we compared the baseline design with five extended configurations, while varying the underlying dust modeling, in each of which the High-Frequency Telescope (HFT) frequency range was shifted logarithmically toward higher frequencies, with an upper cutoff ranging between 400 and 600 GHz. In each case, we measured the tensor-to-scalar ratio r uncertainty and bias using both parametric and minimum-variance component-separation algorithms. When the thermal dust sky model includes a spatially varying spectral index and temperature, we find that the statistical uncertainty on r after foreground cleaning may be reduced by as much as 30–50% by extending the upper limit of the frequency range from 400 to 600 GHz, with most of the improvement already gained at 500 GHz. We also note that a broader frequency range leads to higher residuals when fitting an incorrect dust model, but also it is easier to discriminate between models through higher χ 2 sensitivity. Even in the case in which the fitting procedure does not correspond to the underlying dust model in the sky, and when the highest frequency data cannot be modeled with sufficient fidelity and must be excluded from the analysis, the uncertainty on r increases by only about 5% for a 500 GHz configuration compared to the baseline.

• Eskilt, Johannes Røsok; Lee, Katherine; Watts, Duncan; Anshul, V.; Aurvik, Ragnhild & Basyrov, Artem [Show all 23 contributors for this article] (2023). COSMOGLOBE: Towards end-to-end CMB cosmological parameter estimation without likelihood approximations. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 678. doi: 10.1051/0004-6361/202347358. Full text in Research Archive Show summary

  We implement support for a cosmological parameter estimation algorithm in Commander and quantify its computational efficiency and cost. For a semi-realistic simulation similar to Planck LFI 70 GHz, we find that the computational cost of producing one single sample is about 20 CPU-hours and that the typical Markov chain correlation length is ∼100 samples. The net effective cost per independent sample is ∼2000 CPU-hours, in comparison with all low-level processing costs of 812 CPU-hours for Planck LFI and WMAP in C OSMOGLOBE Data Release 1. Thus, although technically possible to run already in its current state, future work should aim to reduce the effective cost per independent sample by one order of magnitude to avoid excessive runtimes, for instance through multi-grid preconditioners and/or derivative-based Markov chain sampling schemes. This work demonstrates the computational feasibility of true Bayesian cosmological parameter estimation with end-to-end error propagation for high-precision CMB experiments without likelihood approximations, but it also highlights the need for additional optimizations before it is ready for full production-level analysis.

• Svalheim, Trygve Leithe; Andersen, Kristian Joten; Aurvik, Ragnhild; Banerji, Ranajoy; Bersanelli, M. & Bertocco, S. [Show all 38 contributors for this article] (2023). BeyondPlanck: XIV. Polarized foreground emission between 30 and 70 GHz. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202243160. Full text in Research Archive Show summary

  Using the Planck Low Frequency Instrument (LFI) and WMAP data within the global Bayesian B EYOND P LANCK framework, we constrained the polarized foreground emission between 30 and 70 GHz. We combined, for the first time, full-resolution Planck LFI time-ordered data with low-resolution WMAP sky maps at 33, 40, and 61 GHz. The spectral parameters were fit with a likelihood defined at the native resolution of each frequency channel. This analysis represents the first implementation of true multi-resolution component separation applied to CMB observations for both amplitude and spectral energy distribution (SED) parameters. For the synchrotron emission, we approximated the SED as a power-law in frequency and we find that the low signal-to-noise ratio of the current data strongly limits the number of free parameters that can be robustly constrained. We partitioned the sky into four large disjoint regions (High Latitude; Galactic Spur; Galactic Plane; and Galactic Center), each associated with its own power-law index. We find that the High Latitude region is prior-dominated, while the Galactic Center region is contaminated by residual instrumental systematics. The two remaining regions appear to be signal-dominated, and for these we derive spectral indices of β s Spur  = −3.17 ± 0.06 and β s Plane  = −3.03 ± 0.07, which is in good agreement with previous results. For the thermal dust emission, we assumed a modified blackbody model and we fit a single power-law index across the full sky. We find β d  = 1.64 ± 0.03, which is slightly steeper than the value reported in Planck HFI data, but still statistically consistent at the 2 σ confidence level.

• Watts, Duncan; Basyrov, Artem; Eskilt, Johannes Røsok; Galloway, Mathew; Gjerløw, Eirik & Hergt, L.T. [Show all 33 contributors for this article] (2023). COSMOGLOBE DR1 results: I. Improved Wilkinson Microwave Anisotropy Probe maps through Bayesian end-to-end analysis. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 679. doi: 10.1051/0004-6361/202346414. Full text in Research Archive Show summary

  We present C OSMOGLOBE Data Release 1, which implements the first joint analysis of WMAP and Planck LFI time-ordered data, processed within a single Bayesian end-to-end framework. This framework directly builds on a similar analysis of the LFI measurements by the B EYOND P LANCK collaboration, and approaches the cosmic microwave background (CMB) analysis challenge through Gibbs sampling of a global posterior distribution, simultaneously accounting for calibration, mapmaking, and component separation. The computational cost of producing one complete WMAP+LFI Gibbs sample is 812 CPU-h, of which 603 CPU-h are spent on WMAP low-level processing; this demonstrates that end-to-end Bayesian analysis of the WMAP data is computationally feasible. We find that our WMAP posterior mean temperature sky maps and CMB temperature power spectrum are largely consistent with the official WMAP9 results. Perhaps the most notable difference is that our CMB dipole amplitude is 3366.2 ± 1.4 μK, which is 11 μK higher than the WMAP9 estimate and 2.5 σ higher than B EYOND P LANCK ; however, it is in perfect agreement with the HFI-dominated Planck PR4 result. In contrast, our WMAP polarization maps differ more notably from the WMAP9 results, and in general exhibit significantly lower large-scale residuals. We attribute this to a better constrained gain and transmission imbalance model. It is particularly noteworthy that the W -band polarization sky map, which was excluded from the official WMAP cosmological analysis, for the first time appears visually consistent with the V -band sky map. Similarly, the long standing discrepancy between the WMAP K -band and LFI 30 GHz maps is finally resolved, and the difference between the two maps appears consistent with instrumental noise at high Galactic latitudes. Relatedly, these updated maps allowed us for the first time to combine WMAP and LFI polarization data into a single coherent model of large-scale polarized synchrotron emission. Still, we identified a few issues that require additional work, including (1) low-level noise modeling; (2) large-scale temperature residuals at the 1–2 μK level; and (3) a strong degeneracy between the absolute K -band calibration and the dipole of the anomalous microwave emission component. We conclude that leveraging the complementary strengths of WMAP and LFI has allowed the mitigation of both experiments’ weaknesses, and resulted in new state-of-the-art WMAP sky maps. All maps and the associated code are made publicly available through the C OSMOGLOBE web page.

• Herman, Daniel Christopher; Hensley, B.; Andersen, Kristian Joten; Aurvik, Ragnhild; Banerji, Ranajoy & Bersanelli, M. [Show all 36 contributors for this article] (2023). BeyondPlanck: XV. Limits on large-scale polarized anomalous microwave emission from Planck LFI and WMAP. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202243081. Full text in Research Archive Show summary

  We constrained the level of polarized anomalous microwave emission (AME) on large angular scales using Planck Low-Frequency Instrument (LFI) and WMAP polarization data within a Bayesian cosmic microwave background (CMB) analysis framework. We modeled synchrotron emission with a power-law spectral energy distribution, as well as the sum of AME and thermal dust emission through linear regression with the Planck High-Frequency Instrument (HFI) 353 GHz data. This template-based dust emission model allowed us to constrain the level of polarized AME while making minimal assumptions on its frequency dependence. We neglected CMB fluctuations, but show through simulations that these fluctuations have a minor impact on the results. We find that the resulting AME polarization fraction confidence limit is sensitive to the polarized synchrotron spectral index prior. In addition, for prior means β s  &lt; −3.1 we find an upper limit of p AME max  ≲ 0.6% (95% confidence). In contrast, for means β s  = −3.0, we find a nominal detection of p AME  = 2.5 ± 1.0% (95% confidence). These data are thus not strong enough to simultaneously and robustly constrain both polarized synchrotron emission and AME, and our main result is therefore a constraint on the AME polarization fraction explicitly as a function of β s . Combining the current Planck and WMAP observations with measurements from high-sensitivity low-frequency experiments such as C-BASS and QUIJOTE will be critical to improve these limits further.

• Colombo, L.P.L.; Eskilt, Johannes Røsok; Paradiso, S.; Thommesen, Harald; Andersen, Kristian Joten & Aurvik, Ragnhild [Show all 40 contributors for this article] (2023). BeyondPlanck: XI. Bayesian CMB analysis with sample-based end-to-end error propagation. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202244619. Full text in Research Archive
• Gjerløw, Eirik; Ihle, Håvard Tveit; Galeotta, S.; Andersen, Kristian Joten; Aurvik, Ragnhild & Banerji, Ranajoy [Show all 38 contributors for this article] (2023). BeyondPlanck: VII. Bayesian estimation of gain and absolute calibration for cosmic microwave background experiments. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202244061. Full text in Research Archive Show summary

  We present a Bayesian calibration algorithm for cosmic microwave background (CMB) observations as implemented within the global end-to-end B EYOND P LANCK framework and applied to the Planck Low Frequency Instrument (LFI) data. Following the most recent Planck analysis, we decomposed the full time-dependent gain into a sum of three nearly orthogonal components: one absolute calibration term, common to all detectors, one time-independent term that can vary between detectors, and one time-dependent component that was allowed to vary between one-hour pointing periods. Each term was then sampled conditionally on all other parameters in the global signal model through Gibbs sampling. The absolute calibration is sampled using only the orbital dipole as a reference source, while the two relative gain components were sampled using the full sky signal, including the orbital and Solar CMB dipoles, CMB fluctuations, and foreground contributions. We discuss various aspects of the data that influence gain estimation, including the dipole-polarization quadrupole degeneracy and processing masks. Comparing our solution to previous pipelines, we find good agreement in general, with relative deviations of −0.67% (−0.84%) for 30 GHz, 0.12% (−0.04%) for 44 GHz and −0.03% (−0.64%) for 70 GHz, compared to Planck PR4 and Planck 2018, respectively. We note that the B EYOND P LANCK calibration was performed globally, which results in better inter-frequency consistency than previous estimates. Additionally, WMAP observations were used actively in the B EYOND P LANCK analysis, which both breaks internal degeneracies in the Planck data set and results in an overall better agreement with WMAP. Finally, we used a Wiener filtering approach to smoothing the gain estimates. We show that this method avoids artifacts in the correlated noise maps as a result of oversmoothing the gain solution, which is difficult to avoid with methods like boxcar smoothing, as Wiener filtering by construction maintains a balance between data fidelity and prior knowledge. Although our presentation and algorithm are currently oriented toward LFI processing, the general procedure is fully generalizable to other experiments, as long as the Solar dipole signal is available to be used for calibration.

• Paradiso, S.; Colombo, L.P.L.; Andersen, Kristian Joten; Aurvik, Ragnhild; Banerji, Ranajoy & Basyrov, Artem [Show all 41 contributors for this article] (2023). BeyondPlanck: XII. Cosmological parameter constraints with end-to-end error propagation. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202244060. Full text in Research Archive Show summary

  We present cosmological parameter constraints estimated using the Bayesian B EYOND P LANCK analysis framework. This method supports seamless end-to-end error propagation from raw time-ordered data onto final cosmological parameters. As a first demonstration of the method, we analyzed time-ordered Planck LFI observations, combined with selected external data (WMAP 33–61 GHz, Planck HFI DR4 353 and 857 GHz, and Haslam 408 MHz) in the form of pixelized maps that are used to break critical astrophysical degeneracies. Overall, all the results are generally in good agreement with previously reported values from Planck 2018 and WMAP, with the largest relative difference for any parameter amounting about 1 σ when considering only temperature multipoles between 30 ≤  ℓ  ≤ 600. In cases where there are differences, we note that the B EYOND P LANCK results are generally slightly closer to the high- ℓ HFI-dominated Planck 2018 results than previous analyses, suggesting slightly less tension between low and high multipoles. Using low- ℓ polarization information from LFI and WMAP, we find a best-fit value of τ  = 0.066 ± 0.013, which is higher than the low value of τ  = 0.052 ± 0.008 derived from Planck 2018 and slightly lower than the value of 0.069 ± 0.011 derived from the joint analysis of official LFI and WMAP products. Most importantly, however, we find that the uncertainty derived in the B EYOND P LANCK processing is about 30 % greater than when analyzing the official products, after taking into account the different sky coverage. We argue that this uncertainty is due to a marginalization over a more complete model of instrumental and astrophysical parameters, which results in more reliable and more rigorously defined uncertainties. We find that about 2000 Monte Carlo samples are required to achieve a robust convergence for a low-resolution cosmic microwave background (CMB) covariance matrix with 225 independent modes, and producing these samples takes about eight weeks on a modest computing cluster with 256 cores.

• Gerakakis, S.; Brilenkov, Maksym; Ieronymaki, M.; San, Metin; Watts, Duncan & Andersen, Kristian Joten [Show all 42 contributors for this article] (2023). From BeyondPlanck to Cosmoglobe: Open Science, Reproducibility, and Data Longevity. The Open Journal of Astrophysics. 6. doi: 10.21105/astro.2205.11262. Full text in Research Archive Show summary

  The BeyondPlanck and Cosmoglobe collaborations have implemented the first integrated Bayesian end-to-end analysis pipeline for CMB experiments. The primary long-term motivation for this work is to develop a common analysis platform that supports efficient global joint analysis of complementary radio, microwave, and sub-millimeter experiments. A strict prerequisite for this to succeed is broad participation from the CMB community, and two foundational aspects of the program are therefore reproducibility and Open Science. In this paper, we discuss our efforts toward this aim. We also discuss measures toward facilitating easy code and data distribution, community-based code documentation, user-friendly compilation procedures, etc. This work represents the first publicly released end-to-end CMB analysis pipeline that includes raw data, source code, parameter files, and documentation. We argue that such a complete pipeline release should be a requirement for all major future and publicly-funded CMB experiments, noting that a full public release significantly increases data longevity by ensuring that the data quality can be improved whenever better processing techniques, complementary datasets, or more computing power become available, and thereby also taxpayers’ value for money; providing only raw data and final products is not sufficient to guarantee full reproducibility in the future.

• Allys, E.; Arnold, K.; Aumont, J.; Aurvik, Ragnhild; Azzoni, S. & Baccigalupi, C. [Show all 190 contributors for this article] (2023). Probing cosmic inflation with the LiteBIRD cosmic microwave background polarization survey. Progress of Theoretical and Experimental Physics. 2023(4). doi: 10.1093/ptep/ptac150. Full text in Research Archive Show summary

  LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA’s H3 rocket. LiteBIRD is planned to orbit the Sun–Earth Lagrangian point L2, where it will map the cosmic microwave background polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of 2.2μK-arcmin, with a typical angular resolution of 0.5○ at 100 GHz. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions, and synergies with other projects.

• Watts, Duncan; Galloway, Mathew; Ihle, Håvard Tveit; Andersen, Kristian Joten; Aurvik, Ragnhild & Banerji, Ranajoy [Show all 43 contributors for this article] (2023). From BeyondPlanck to Cosmoglobe: Preliminary WMAP Q-band analysis. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202243410. Full text in Research Archive Show summary

  We present the first application of the C OSMOGLOBE analysis framework by analyzing nine-year WMAP time-ordered observations that uses similar machinery to that of B EYOND P LANCK for the Planck Low Frequency Instrument (LFI). We analyzed only the Q -band (41 GHz) data and report on the low-level analysis process based on uncalibrated time-ordered data to calibrated maps. Most of the existing B EYOND P LANCK pipeline may be reused for WMAP analysis with minimal changes to the existing codebase. The main modification is the implementation of the same preconditioned biconjugate gradient mapmaker used by the WMAP team. Producing a single WMAP Q 1-band sample requires 22 CPU-hrs, which is slightly more than the cost of a Planck 44 GHz sample of 17 CPU-hrs; this demonstrates that a full end-to-end Bayesian processing of the WMAP data is computationally feasible. In general, our recovered maps are very similar to the maps released by the WMAP team, although with two notable differences. In terms of temperature, we find a ∼2 μK quadrupole difference that most likely is caused by different gain modeling, while in polarization we find a distinct 2.5 μK signal that has been previously referred to as poorly measured modes by the WMAP team. In the C OSMOGLOBE processing, this pattern arises from temperature-to-polarization leakage from the coupling between the CMB Solar dipole, transmission imbalance, and sidelobes. No traces of this pattern are found in either the frequency map or TOD residual map, suggesting that the current processing has succeeded in modeling these poorly measured modes within the assumed parametric model by using Planck information to break the sky-synchronous degeneracies inherent in the WMAP scanning strategy.

• Basyrov, Artem; Suur-Uski, A.-S.; Colombo, L.P.L.; Eskilt, Johannes Røsok; Paradiso, S. & Andersen, Kristian Joten [Show all 40 contributors for this article] (2023). BeyondPlanck: X. Planck Low Frequency Instrument frequency maps with sample-based error propagation. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202244819. Full text in Research Archive Show summary

  We present Planck Low Frequency Instrument (LFI) frequency sky maps derived within the B EYOND P LANCK framework. This framework draws samples from a global posterior distribution that includes instrumental, astrophysical, and cosmological parameters, and the main product is an entire ensemble of frequency sky map samples, each of which corresponds to one possible realization of the various modeled instrumental systematic corrections, including correlated noise, time-variable gain, as well as far sidelobe and bandpass corrections. This ensemble allows for computationally convenient end-to-end propagation of low-level instrumental uncertainties into higher-level science products, including astrophysical component maps, angular power spectra, and cosmological parameters. We show that the two dominant sources of LFI instrumental systematic uncertainties are correlated noise and gain fluctuations, and the products presented here support – for the first time – full Bayesian error propagation for these effects at full angular resolution. We compared our posterior mean maps with traditional frequency maps delivered by the Planck Collaboration, and find generally good agreement. The most important quality improvement is due to significantly lower calibration uncertainties in the new processing, as we find a fractional absolute calibration uncertainty at 70 GHz of Δ g 0 / g 0  = 5 × 10 −5 , which is nominally 40 times smaller than that reported by Planck 2018. However, we also note that the original Planck 2018 estimate has a nontrivial statistical interpretation, and this further illustrates the advantage of the new framework in terms of producing self-consistent and well-defined error estimates of all involved quantities without the need of ad hoc uncertainty contributions. We describe how low-resolution data products, including dense pixel-pixel covariance matrices, may be produced from the posterior samples directly, without the need for computationally expensive analytic calculations or simulations. We conclude that posterior-based frequency map sampling provides unique capabilities in terms of low-level systematics modeling and error propagation, and may play an important role for future Cosmic Microwave Background (CMB) B -mode experiments aiming at nanokelvin precision.

• Galloway, Mathew; Reinecke, M.; Andersen, Kristian Joten; Aurvik, Ragnhild; Banerji, Ranajoy & Bersanelli, M. [Show all 41 contributors for this article] (2023). BeyondPlanck: VIII. Efficient sidelobe convolution and corrections through spin harmonics. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202243138. Full text in Research Archive Show summary

  We introduce a new formulation of the Conviqt convolution algorithm in terms of spin harmonics, and apply this to the problem of sidelobe correction for B EYOND P LANCK , the first end-to-end Bayesian Gibbs sampling framework for CMB analysis. We compare our implementation to the previous Planck LevelS implementation, and find good agreement between the two codes in terms of accuracy, but with a speed-up reaching a factor of 3–10, depending on the frequency bandlimits, l max and m max . The new algorithm is significantly simpler to implement and maintain, since all low-level calculations are handled through an external spherical harmonic transform library. We find that our mean sidelobe estimates for Planck LFI are in good agreement with previous efforts. Additionally, we present novel sidelobe rms maps that quantify the uncertainty in the sidelobe corrections due to variations in the sky model.

• Galloway, Mathew; Andersen, Kristian Joten; Aurvik, Ragnhild; Banerji, Ranajoy; Bersanelli, M. & Bertocco, S. [Show all 41 contributors for this article] (2023). BeyondPlanck: III. Commander3. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202243137. Full text in Research Archive Show summary

  We describe the computational infrastructure for end-to-end Bayesian cosmic microwave background (CMB) analysis implemented by the BeyondPlanck Collaboration. The code is called Commander3 . It provides a statistically consistent framework for global analysis of CMB and microwave observations and may be useful for a wide range of legacy, current, and future experiments. The paper has three main goals. Firstly, we provide a high-level overview of the existing code base, aiming to guide readers who wish to extend and adapt the code according to their own needs or re-implement it from scratch in a different programming language. Secondly, we discuss some critical computational challenges that arise within any global CMB analysis framework, for instance in-memory compression of time-ordered data, fast Fourier transform optimization, and parallelization and load-balancing. Thirdly, we quantify the CPU and RAM requirements for the current B EYOND P LANCK analysis, finding that a total of 1.5 TB of RAM is required for efficient analysis and that the total cost of a full Gibbs sample for LFI is 170 CPU-hrs, including both low-level processing and high-level component separation, which is well within the capabilities of current low-cost computing facilities. The existing code base is made publicly available under a GNU General Public Library (GPL) license.

• Keihänen, Elina; Suur-Uski, A.-S.; Andersen, Kristian Joten; Aurvik, Ragnhild; Banerji, Ranajoy & Basyrov, Artem [Show all 42 contributors for this article] (2023). BeyondPlanck: II. CMB mapmaking through Gibbs sampling. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202142799. Full text in Research Archive Show summary

  We present a Gibbs sampling solution to the mapmaking problem for cosmic microwave background (CMB) measurements that builds on existing destriping methodology. Gibbs sampling breaks the computationally heavy destriping problem into two separate steps: noise filtering and map binning. Considered as two separate steps, both are computationally much cheaper than solving the combined problem. This provides a huge performance benefit as compared to traditional methods and it allows us, for the first time, to bring the destriping baseline length to a single sample. Here, we applied the Gibbs procedure to simulated Planck 30 GHz data. We find that gaps in the time-ordered data are handled efficiently by filling them in with simulated noise as part of the Gibbs process. The Gibbs procedure yields a chain of map samples, from which we are able to compute the posterior mean as a best-estimate map. The variation in the chain provides information on the correlated residual noise, without the need to construct a full noise covariance matrix. However, if only a single maximum-likelihood frequency map estimate is required, we find that traditional conjugate gradient solvers converge much faster than a Gibbs sampler in terms of the total number of iterations. The conceptual advantages of the Gibbs sampling approach lies in statistically well-defined error propagation and systematic error correction. This methodology thus forms the conceptual basis for the mapmaking algorithm employed in the B EYOND P LANCK framework, which implements the first end-to-end Bayesian analysis pipeline for CMB observations.

• Herman, Daniel Christopher; Watson, R.A.; Andersen, Kristian Joten; Aurvik, Ragnhild; Banerji, Ranajoy & Bersanelli, M. [Show all 40 contributors for this article] (2023). BeyondPlanck: V. Minimal ADC Corrections for Planck LFI. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202243639. Full text in Research Archive Show summary

  We describe the correction procedure for Analog-to-Digital Converter (ADC) differential non-linearities (DNL) adopted in the Bayesian end-to-end B EYOND P LANCK analysis framework. This method is nearly identical to that developed for the official Planck Low Frequency Instrument (LFI) Data Processing Center (DPC) analysis, and relies on the binned rms noise profile of each detector data stream. However, rather than building the correction profile directly from the raw rms profile, we first fit a Gaussian to each significant ADC-induced rms decrement, and then derive the corresponding correction model from this smooth model. The main advantage of this approach is that only samples which are significantly affected by ADC DNLs are corrected, as opposed to the DPC approach in which the correction is applied to all samples, filtering out signals not associated with ADC DNLs. The new corrections are only applied to data for which there is a clear detection of the non-linearities, and for which they perform at least comparably with the DPC corrections. Out of a total of 88 LFI data streams (sky and reference load for each of the 44 detectors) we apply the new minimal ADC corrections in 25 cases, and maintain the DPC corrections in 8 cases. All these corrections are applied to 44 or 70 GHz channels, while, as in previous analyses, none of the 30 GHz ADCs show significant evidence of non-linearity. By comparing the B EYOND P LANCK and DPC ADC correction methods, we estimate that the residual ADC uncertainty is about two orders of magnitude below the total noise of both the 44 and 70 GHz channels, and their impact on current cosmological parameter estimation is small. However, we also show that non-idealities in the ADC corrections can generate sharp stripes in the final frequency maps, and these could be important for future joint analyses with the Planck High Frequency Instrument (HFI), Wilkinson Microwave Anisotropy Probe (WMAP), or other datasets. We therefore conclude that, although the existing corrections are adequate for LFI-based cosmological parameter analysis, further work on LFI ADC corrections is still warranted.

• Andersen, Kristian Joten; Aurvik, Ragnhild; Banerji, Ranajoy; Basyrov, Artem; Bersanelli, M. & Bertocco, S. [Show all 44 contributors for this article] (2023). BeyondPlanck: I. Global Bayesian analysis of the Planck Low Frequency Instrument data. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202244953. Full text in Research Archive Show summary

  We describe the B EYOND P LANCK project in terms of our motivation, methodology, and main products, and provide a guide to a set of companion papers that describe each result in more detail. Building directly on experience from ESA’s Planck mission, we implemented a complete end-to-end Bayesian analysis framework for the Planck Low Frequency Instrument (LFI) observations. The primary product is a full joint posterior distribution P ( ω  ∣  d ), where ω represents the set of all free instrumental (gain, correlated noise, bandpass, etc.), astrophysical (synchrotron, free-free, thermal dust emission, etc.), and cosmological (cosmic microwave background – CMB – map, power spectrum, etc.) parameters. Some notable advantages of this approach compared to a traditional pipeline procedure are seamless end-to-end propagation of uncertainties; accurate modeling of both astrophysical and instrumental effects in the most natural basis for each uncertain quantity; optimized computational costs with little or no need for intermediate human interaction between various analysis steps; and a complete overview of the entire analysis process within one single framework. As a practical demonstration of this framework, we focus in particular on low- ℓ CMB polarization reconstruction with Planck LFI. In this process, we identify several important new effects that have not been accounted for in previous pipelines, including gain over-smoothing and time-variable and non-1/ f correlated noise in the 30 and 44 GHz channels. Modeling and mitigating both previously known and newly discovered systematic effects, we find that all results are consistent with the ΛCDM model, and we constrained the reionization optical depth to τ  = 0.066 ± 0.013, with a low-resolution CMB-based χ 2 probability to exceed of 32%. This uncertainty is about 30% larger than the official pipelines, arising from taking a more complete instrumental model into account. The marginal CMB solar dipole amplitude is 3362.7 ± 1.4 μK, where the error bar was derived directly from the posterior distribution without the need of any ad hoc instrumental corrections. We are currently not aware of any significant unmodeled systematic effects remaining in the Planck LFI data, and, for the first time, the 44 GHz channel is fully exploited in the current analysis. We argue that this framework can play a central role in the analysis of many current and future high-sensitivity CMB experiments, including LiteBIRD, and it will serve as the computational foundation of the emerging community-wide C OSMOGLOBE effort, which aims to combine state-of-the-art radio, microwave, and submillimeter data sets into one global astrophysical model.

• Andersen, Kristian Joten; Herman, Daniel Christopher; Aurvik, Ragnhild; Banerji, Ranajoy; Basyrov, Artem & Bersanelli, M. [Show all 44 contributors for this article] (2023). BeyondPlanck: XIII. Intensity foreground sampling, degeneracies, and priors. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202243186. Full text in Research Archive Show summary

  We present the intensity foreground algorithms and model employed within the B EYOND P LANCK analysis framework. The B EYOND P LANCK analysis is aimed at integrating component separation and instrumental parameter sampling within a global framework, leading to complete end-to-end error propagation in the Planck Low Frequency Instrument (LFI) data analysis. Given the scope of the B EYOND P LANCK analysis, a limited set of data is included in the component separation process, leading to foreground parameter degeneracies. In order to properly constrain the Galactic foreground parameters, we improve upon the previous Commander component separation implementation by adding a suite of algorithmic techniques. These algorithms are designed to improve the stability and computational efficiency for weakly constrained posterior distributions. These are: (1) joint foreground spectral parameter and amplitude sampling, building on ideas from M IRAMARE ; (2) component-based monopole determination; (3) joint spectral parameter and monopole sampling; and (4) application of informative spatial priors for component amplitude maps. We find that the only spectral parameter with a significant signal-to-noise ratio using the current B EYOND P LANCK data set is the peak frequency of the anomalous microwave emission component, for which we find ν p  = 25.3 ± 0.5 GHz; all others must be constrained through external priors. Future works will be aimed at integrating many more data sets into this analysis, both map and time-ordered based, thereby gradually eliminating the currently observed degeneracies in a controlled manner with respect to both instrumental systematic effects and astrophysical degeneracies. When this happens, the simple LFI-oriented data model employed in the current work will need to be generalized to account for both a richer astrophysical model and additional instrumental effects. This work will be organized within the Open Science-based C OSMOGLOBE community effort.

• Ihle, Håvard Tveit; Bersanelli, M.; Franceschet, C.; Gjerløw, Eirik; Andersen, Kristian Joten & Aurvik, Ragnhild [Show all 41 contributors for this article] (2023). BeyondPlanck: VI. Noise characterization and modeling. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202243619. Full text in Research Archive Show summary

  We present a Bayesian method for estimating instrumental noise parameters and propagating noise uncertainties within the global BEYONDPLANCK Gibbs sampling framework, which we applied to Planck Low Frequency Instrument (LFI) time-ordered data. Following previous works in the literature, we initially adopted a 1/f model for the noise power spectral density (PSD), but we found the need for an additional lognormal component in the noise model in the 30 and 44 GHz bands. We implemented an optimal Wiener-filter (or constrained realization) gap-filling procedure to account for masked data. We then used this procedure to both estimate the gapless correlated noise in the time-domain, ncorr, and to sample the noise PSD parameters, ξn = {σ0, fknee, α, Ap}. In contrast to previous Planck analyses, we assumed piecewise stationary noise only within each pointing period (PID), and not throughout the full mission, but we adopted the LFI Data Processing Center results as priors on α and fknee. We generally found best-fit correlated noise parameters that are mostly consistent with previous results, with a few notable exceptions. However, a detailed inspection of the time-dependent results has revealed many important findings. First and foremost, we find strong evidence for statistically significant temporal variations in all noise PSD parameters, many of which are directly correlated with satellite housekeeping data. Second, while the simple 1/f model appears to be an excellent fit for the LFI 70 GHz channel, there is evidence for additional correlated noise that is not described by a 1/f model in the 30 and 44 GHz channels, including within the primary science frequency range of 0.1–1 Hz. In general, most 30 and 44 GHz channels exhibit deviations from 1/f at the 2–3σ level in each one-hour pointing period, motivating the addition of the lognormal noise component for these bands. For certain periods of time, we also find evidence of strong common mode noise fluctuations across the entire focal plane. Overall, we conclude that a simple 1/f profile is not adequate for obtaining a full characterization of the Planck LFI noise, even when fitted hour-by-hour, and a more general model is required. These findings have important implications for large-scale CMB polarization reconstruction with the Planck LFI data and the current work is a first attempt at understanding and mitigating these issues.

• Svalheim, Trygve Leithe; Zonca, A.; Andersen, Kristian Joten; Aurvik, Ragnhild; Banerji, Ranajoy & Bersanelli, M. [Show all 39 contributors for this article] (2023). BeyondPlanck: IX. Bandpass and beam leakage corrections. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 675. doi: 10.1051/0004-6361/202243080. Full text in Research Archive Show summary

  We discuss the treatment of bandpass and beam leakage corrections in the Bayesian B EYOND P LANCK cosmic microwave background (CMB) analysis pipeline as applied to the Planck LFI measurements. As a preparatory step, we first applied three corrections to the nominal LFI bandpass profiles, including the removal of a known systematic effect in the ground measuring equipment at 61 GHz, along with a smoothing of standing wave ripples and edge regularization. The main net impact of these modifications is an overall shift in the 70 GHz bandpass of +0.6 GHz. We argue that any analysis of LFI data products, either from Planck or B EYOND P LANCK , should use these new bandpasses. In addition, we fit a single free bandpass parameter for each radiometer of the form Δ i  = Δ 0  +  δ i , where Δ 0 represents an absolute frequency shift per frequency band and δ i is a relative shift per detector. The absolute correction is only fitted at 30 GHz, with a full χ 2 -based likelihood, resulting in a correction of Δ 30  = 0.24 ± 0.03 GHz. The relative corrections were fitted using a spurious map approach that is fundamentally similar to the method pioneered by the WMAP team, but excluding the introduction of many additional degrees of freedom. All the bandpass parameters were sampled using a standard Metropolis sampler within the main B EYOND P LANCK Gibbs chain and the bandpass uncertainties were thus propagated to all other data products in the analysis. In summary, we find that our bandpass model significantly reduces leakage effects. For beam leakage corrections, we adopted the official Planck LFI beam estimates without any additional degrees of freedom and we only marginalized over the underlying sky model. We note that this is the first time that leakage from beam mismatch has been included for Planck LFI maps.

• Ade, Peter A.R.; Amiri, M.; Benton, S.J.; Bergman, A.S.; Bihary, R. & Bock, J.J. [Show all 70 contributors for this article] (2022). A Constraint on Primordial B-modes from the First Flight of the Spider Balloon-borne Telescope. The Astrophysical Journal (ApJ). ISSN 0004-637X. 927(2). doi: 10.3847/1538-4357/ac20df. Full text in Research Archive Show summary

  We present the first linear polarization measurements from the 2015 long-duration balloon flight of Spider, which is an experiment that is designed to map the polarization of the cosmic microwave background (CMB) on degree angular scales. The results from these measurements include maps and angular power spectra from observations of 4.8% of the sky at 95 and 150 GHz, along with the results of internal consistency tests on these data. While the polarized CMB anisotropy from primordial density perturbations is the dominant signal in this region of sky, Galactic dust emission is also detected with high significance. Galactic synchrotron emission is found to be negligible in the Spider bands. We employ two independent foreground-removal techniques to explore the sensitivity of the cosmological result to the assumptions made by each. The primary method uses a dust template derived from Planck data to subtract the Galactic dust signal. A second approach, which constitutes a joint analysis of Spider and Planck data in the harmonic domain, assumes a modified-blackbody model for the spectral energy distribution of the dust with no constraint on its spatial morphology. Using a likelihood that jointly samples the template amplitude and r parameter space, we derive 95% upper limits on the primordial tensor-to-scalar ratio from Feldman–Cousins and Bayesian constructions, finding r < 0.11 and r < 0.19, respectively. Roughly half the uncertainty in r derives from noise associated with the template subtraction. New data at 280 GHz from Spider's second flight will complement the Planck polarization maps, providing powerful measurements of the polarized Galactic dust emission.

• Krachmalnicoff, N.; Matsumura, T.; Hoz, E. de la; Basak, S.; Gruppuso, A. & Minami, Y. [Show all 70 contributors for this article] (2022). In-flight polarization angle calibration for LiteBIRD: Blind challenge and cosmological implications. Journal of Cosmology and Astroparticle Physics (JCAP). 2022(1). doi: 10.1088/1475-7516/2022/01/039. Full text in Research Archive
• Vielva, P.; Martínez-González, E.; Casas, F.J.; Matsumura, T.; Henrot-Versillé, S. & Komatsu, E. [Show all 71 contributors for this article] (2022). Polarization angle requirements for CMB B-mode experiments. Application to the LiteBIRD satellite. Journal of Cosmology and Astroparticle Physics (JCAP). 2022(4). doi: 10.1088/1475-7516/2022/04/029. Full text in Research Archive
• Shaaban, Mohamed M.; Gill, Ajay S.; McCleary, Jacqueline; Massey, Richard; Benton, Steven J. & Brown, Anthony M. [Show all 28 contributors for this article] (2022). Weak Lensing in the Blue: A Counter-intuitive Strategy for Stratospheric Observations. Astronomical Journal. ISSN 0004-6256. 164(6). doi: 10.3847/1538-3881/ac9b1c. Full text in Research Archive Show summary

  Abstract The statistical power of weak lensing measurements is principally driven by the number of high-redshift galaxies whose shapes are resolved. Conventional wisdom and physical intuition suggest this is optimized by deep imaging at long (red or near-IR) wavelengths, to avoid losing redshifted Balmer-break and Lyman-break galaxies. We use the synthetic Emission Line (“EL”)-COSMOS catalog to simulate lensing observations using different filters, from various altitudes. Here were predict the number of exposures to achieve a target z ≳ 0.3 source density, using off-the-shelf and custom filters. Ground-based observations are easily better at red wavelengths, as (more narrowly) are space-based observations. However, we find that SuperBIT , a diffraction-limited observatory operating in the stratosphere, should instead perform its lensing-quality observations at blue wavelengths.

• Hasebe, T.; Ade, P.A.R.; Adler, A.; Allys, E.; Alonso, D. & Arnold, K. [Show all 281 contributors for this article] (2022). Sensitivity Modeling for LiteBIRD. Journal of Low Temperature Physics. ISSN 0022-2291. doi: 10.1007/s10909-022-02921-7. Full text in Research Archive
• Filippini, J.P.; Gambrel, A.E.; Rahlin, A.S.; Young, E.Y.; Ade, P.A.R. & Amiri, M. [Show all 70 contributors for this article] (2022). In-Flight Gain Monitoring of SPIDER’s Transition-Edge Sensor Arrays. Journal of Low Temperature Physics. ISSN 0022-2291. 209(3-4), p. 649–657. doi: 10.1007/s10909-022-02729-5. Full text in Research Archive
• Hubmayr, J.; Ade, P.A.R.; Adler, A.; Allys, E.; Alonso, D. & Arnold, K. [Show all 320 contributors for this article] (2022). Optical Characterization of OMT-Coupled TES Bolometers for LiteBIRD. Journal of Low Temperature Physics. ISSN 0022-2291. 209(3-4), p. 396–408. doi: 10.1007/s10909-022-02808-7. Full text in Research Archive
• Leung, Jason S.-Y.; Hartley, J.; Nagy, J.M.; Netterfield, C.B.; Shariff, J.A. & Ade, P.A.R. [Show all 70 contributors for this article] (2022). A Simulation-based Method for Correcting Mode Coupling in CMB Angular Power Spectra. The Astrophysical Journal (ApJ). ISSN 0004-637X. 928(2). doi: 10.3847/1538-4357/ac562f. Full text in Research Archive Show summary

  Modern cosmic microwave background (CMB) analysis pipelines regularly employ complex time-domain filters, beam models, masking, and other techniques during the production of sky maps and their corresponding angular power spectra. However, these processes can generate couplings between multipoles from the same spectrum and from different spectra, in addition to the typical power attenuation. Within the context of pseudo-Cℓ based, MASTER-style analyses, the net effect of the time-domain filtering is commonly approximated by a multiplicative transfer function, Fℓ, that can fail to capture mode mixing and is dependent on the spectrum of the signal. To address these shortcomings, we have developed a simulation-based spectral correction approach that constructs a two-dimensional transfer matrix, ${J}_{{\ell }{\ell }^{\prime} }$, which contains information about mode mixing in addition to mode attenuation. We demonstrate the application of this approach on data from the first flight of the Spider balloon-borne CMB experiment.

• San, Metin; Erikstad, Gustav Bredal; Galloway, Mathew & Watts, Duncan (2022). COSMOGLOBE: Simulating zodiacal emission with ZodiPy. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 666. doi: 10.1051/0004-6361/202244133. Full text in Research Archive Show summary

  We present ZodiPy, a modern and easy-to-use Python package for modeling the zodiacal emission seen by an arbitrary Solar System observer, which can be used for the removal of both thermal emission and scattered sunlight from interplanetary dust in astrophysical data. The code implements the COBE Diffuse Infrared Background Experiment (DIRBE) interplanetary dust model and the Planck extension, which allows for zodiacal emission predictions at infrared wavelengths in the 1.25–240 µm range and at microwave frequencies in the 30–857 GHz range. The predicted zodiacal emission may be extrapolated to frequencies and wavelengths not covered by the built-in models to produce forecasts for future experiments. ZodiPy attempts to enable the development of new interplanetary dust models by providing the community with an easy-to-use interface for testing both current and future models. We demonstrate how the software can be used by creating simulated zodiacal emission timestreams for the DIRBE experiment and show that these agree with corresponding timestreams produced with the DIRBE Zodiacal Light Prediction Software. We also make binned maps of the zodiacal emission as predicted to be observed by DIRBE and compare them with the DIRBE calibrated individual observations (CIO).

• Fuskeland, Unni; Andersen, Kristian Joten; Aurlien, Ragnhild; Banerji, Ranajoy; Brilenkov, Maksym & Eriksen, Hans Kristian Kamfjord [Show all 11 contributors for this article] (2021). Constraints on the spectral index of polarized synchrotron emission from WMAP and Faraday-corrected S-PASS data. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 646. doi: 10.1051/0004-6361/202037629. Full text in Research Archive Show summary

  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.

• Gambrel, Anne E.; Rahlin, Alexandra S.; Song, X.; Contaldi, Carlo R.; Ade, Peter A.R. & Amiri, M. [Show all 67 contributors for this article] (2021). The XFaster Power Spectrum and Likelihood Estimator for the Analysis of Cosmic Microwave Background Maps. The Astrophysical Journal (ApJ). ISSN 0004-637X. 922(2). doi: 10.3847/1538-4357/ac230b. Full text in Research Archive
• Hazumi, Masashi; Ade, Peter A.R.; Adler, A.; Allys, E.; Arnold, K & Auguste, D. [Show all 238 contributors for this article] (2020). LiteBIRD satellite: JAXA's new strategic L-class mission for all-sky surveys of cosmic microwave background polarization. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 11443. doi: 10.1117/12.2563050. Full text in Research Archive Show summary

  LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. JAXA selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with its expected launch in the late 2020s using JAXA's H3 rocket. LiteBIRD plans to map the cosmic microwave background (CMB) polarization over the full sky with unprecedented precision. Its main scientific objective is to carry out a definitive search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with an insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. To this end, LiteBIRD will perform full-sky surveys for three years at the Sun-Earth Lagrangian point L2 for 15 frequency bands between 34 and 448 GHz with three telescopes, to achieve a total sensitivity of 2.16 μK-arcmin with a typical angular resolution of 0.5° at 100 GHz. We provide an overview of the LiteBIRD project, including scientific objectives, mission requirements, top-level system requirements, operation concept, and expected scientific outcomes.

• Montier, Ludovic; Mot, B; Bernardis, P. de; Maffei, B; Pisano, G & Columbro, F [Show all 236 contributors for this article] (2020). Overview of the medium and high frequency telescopes of the LiteBIRD space mission. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 11443. doi: 10.1117/12.2562243. Full text in Research Archive Show summary

  LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular scales, and over 15 frequency bands from 34 GHz to 448 GHz. The LiteBIRD instruments consist of three telescopes, namely the Low-, Medium-and High-Frequency Telescope (respectively LFT, MFT and HFT). We present in this paper an overview of the design of the Medium-Frequency Telescope (89{224 GHz) and the High-Frequency Telescope (166{448 GHz), the so-called MHFT, under European responsibility, which are two cryogenic refractive telescopes cooled down to 5 K. They include a continuous rotating half-wave plate as the first optical element, two high-density polyethylene (HDPE) lenses and more than three thousand transition-edge sensor (TES) detectors cooled to 100 mK. We provide an overview of the concept design and the remaining specific challenges that we have to face in order to achieve the scientific goals of LiteBIRD.

• Sekimoto, Yutaro; Ade, Peter A.R.; Adler, A.; Allys, E.; Arnold, K & Auguste, D. [Show all 237 contributors for this article] (2020). Concept design of low frequency telescope for CMB B-mode polarization satellite LiteBIRD. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 11453. doi: 10.1117/12.2561841. Full text in Research Archive Show summary

  LiteBIRD has been selected as JAXA’s strategic large mission in the 2020s, to observe the cosmic microwave background (CMB) B-mode polarization over the full sky at large angular scales. The challenges of LiteBIRD are the wide field-of-view (FoV) and broadband capabilities of millimeter-wave polarization measurements, which are derived from the system requirements. The possible paths of stray light increase with a wider FoV and the far sidelobe knowledge of -56 dB is a challenging optical requirement. A crossed-Dragone configuration was chosen for the low frequency telescope (LFT : 34–161 GHz), one of LiteBIRD’s onboard telescopes. It has a wide field-of-view (18° x 9°) with an aperture of 400 mm in diameter, corresponding to an angular resolution of about 30 arcminutes around 100 GHz. The focal ratio f/3.0 and the crossing angle of the optical axes of 90◦ are chosen after an extensive study of the stray light. The primary and secondary reflectors have rectangular shapes with serrations to reduce the diffraction pattern from the edges of the mirrors. The reflectors and structure are made of aluminum to proportionally contract from warm down to the operating temperature at 5 K. A 1/4 scaled model of the LFT has been developed to validate the wide field-of-view design and to demonstrate the reduced far sidelobes. A polarization modulation unit (PMU), realized with a half-wave plate (HWP) is placed in front of the aperture stop, the entrance pupil of this system. A large focal plane with approximately 1000 AlMn TES detectors and frequency multiplexing SQUID amplifiers is cooled to 100 mK. The lens and sinuous antennas have broadband capability. Performance specifications of the LFT and an outline of the proposed verification plan are presented.

• Romualdez, L. Javier; Benton, Steven J.; Brown, Anthony M.; Clark, Paul; Damaren, Christopher J. & Eifler, Tim [Show all 29 contributors for this article] (2020). Robust diffraction-limited near-infrared-to-near-ultraviolet wide-field imaging from stratospheric balloon-borne platforms—Super-pressure Balloon-borne Imaging Telescope performance. Review of Scientific Instruments. ISSN 0034-6748. 91(3). doi: 10.1063/1.5139711. Full text in Research Archive Show summary

  At a fraction of the total cost of an equivalent orbital mission, scientific balloon-borne platforms, operating above 99.7% of the Earth’s atmosphere, offer attractive, competitive, and effective observational capabilities—namely, space-like seeing, transmission, and backgrounds—which are well suited for modern astronomy and cosmology. The Super-pressure Balloon-borne Imaging Telescope (SUPERBIT) is a diffraction-limited, wide-field, 0.5 m telescope capable of exploiting these observing conditions in order to provide exquisite imaging throughout the near-infrared to near-ultraviolet. It utilizes a robust active stabilization system that has consistently demonstrated a 48 mas 1σ sky-fixed pointing stability over multiple 1 h observations at float. This is achieved by actively tracking compound pendulations via a three-axis gimballed platform, which provides sky-fixed telescope stability at < 500 mas and corrects for field rotation, while employing high-bandwidth tip/tilt optics to remove residual disturbances across the science imaging focal plane. SUPERBIT’s performance during the 2019 commissioning flight benefited from a customized high-fidelity science-capable telescope designed with an exceptional thermo- and opto-mechanical stability as well as a tightly constrained static and dynamic coupling between high-rate sensors and telescope optics. At the currently demonstrated level of flight performance, SUPERBIT capabilities now surpass the science requirements for a wide variety of experiments in cosmology, astrophysics, and stellar dynamics.

• Sirks, Ellen L.; Clark, P.; Massey, Richard J.; Benton, S. J.; Brown, A. M. & Damaren, Christopher J. [Show all 29 contributors for this article] (2020). Download by parachute: retrieval of assets from high altitude balloons. Journal of Instrumentation (JINST). 15. doi: 10.1088/1748-0221/15/05/P05014. Full text in Research Archive Show summary

  We present a publicly-available toolkit of flight-proven hardware and software to retrieve 5 TB of data or small physical samples from a stratospheric balloon platform. Before launch, a capsule is attached to the balloon, and rises with it. Upon remote command, the capsule is released and descends via parachute, continuously transmitting its location. Software to predict the trajectory can be used to select a safe but accessible landing site. We dropped two such capsules from the SUPERBIT telescope, in September 2019. The capsules took ~37 minutes to descend from ~30 km altitude. They drifted 32 km and 19 km horizontally, but landed within 300 m and 600 m of their predicted landing sites. We found them easily, and successfully recovered the data. We welcome interest from other balloon teams for whom the technology would be useful.

• Thommesen, Harald; Andersen, Kristian Joten; Aurlien, Ragnhild; Banerji, Ranajoy; Brilenkov, Maksym & Fuskeland, Unni [Show all 11 contributors for this article] (2020). A Monte Carlo comparison between template-based and Wiener-filter CMB dipole estimators. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 643. doi: 10.1051/0004-6361/202038905. Full text in Research Archive Show summary

  We review and compare two different cosmic microwave background (CMB) dipole estimators discussed in the literature and assess their performances through Monte Carlo simulations. The first method amounts to simple template regression with partial sky data, while the second method is an optimal Wiener filter (or Gibbs sampling) implementation. The main difference between the two methods is that the latter approach takes into account correlations with higher-order CMB temperature fluctuations that arise from nonorthogonal spherical harmonics on an incomplete sky, which for recent CMB data sets (such as Planck ) is the dominant source of uncertainty. For an accepted sky fraction of 81% and an angular CMB power spectrum corresponding to the best-fit Planck 2018 ΛCDM model, we find that the uncertainty on the recovered dipole amplitude is about six times smaller for the Wiener filter approach than for the template approach, corresponding to 0.5 and 3 μ K, respectively. Similar relative differences are found for the corresponding directional parameters and other sky fractions. We note that the Wiener filter algorithm is generally applicable to any dipole estimation problem on an incomplete sky, as long as a statistical and computationally tractable model is available for the unmasked higher-order fluctuations. The methodology described in this paper forms the numerical basis for the most recent determination of the CMB solar dipole from Planck , as summarized by Planck Collaboration Int. LVII (2020).

• Gill, Ajay; Benton, Steven J.; Brown, Anthony M.; Clark, Paul; Damaren, Christopher J. & Eifler, Tim [Show all 30 contributors for this article] (2020). Optical Night Sky Brightness Measurements from the Stratosphere. Astronomical Journal. ISSN 0004-6256. 160(6). doi: 10.3847/1538-3881/abbffb. Full text in Research Archive
• Gualtieri, Riccardo; Filippini, Jeffrey P.; Ade, Peter A.R.; Amiri, Mandana; Benton, Steven J. & Bergman, A. Stevie [Show all 64 contributors for this article] (2018). SPIDER: CMB Polarimetry from the Edge of Space. Journal of Low Temperature Physics. ISSN 0022-2291. 193(5-6), p. 1112–1121. doi: 10.1007/s10909-018-2078-x. Full text in Research Archive

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• Romualdez, L. J.; Benton, S. J.; Brown, Anthony M.; Clark, Paul; Damaren, Christopher J. & Eifler, Tim [Show all 29 contributors for this article] (2021). Erratum: Robust diffraction-limited near-infrared-to-near-ultraviolet wide-field imaging from stratospheric balloon-borne Platforms-Super-pressure Balloon-borne Imaging Telescope performance (Review of Scientific Instruments (2020) 91 (034501) DOI: 10.1063/1.5139711). Review of Scientific Instruments. ISSN 0034-6748. 92(1). doi: 10.1063/5.0040187. Full text in Research Archive

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