BeyondPlanck XIII. Intensity foreground sampling, degeneracies, and priors

Abstract

We present the intensity foreground algorithms and model employed within the BeyondPlanck analysis framework. The BeyondPlanck 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 BeyondPlanck 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 $\text{Commander}$ 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 Miramare; 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 BeyondPlanck data set is the peak frequency of the anomalous microwave emission component, for which we find ${\nu }_{\mathrm{p}}=25.3\pm 0.5$ 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.

27 pages, 23 figures, 3 tables, part 13 of the BeyondPlanck release. All BeyondPlanck products and software will be released publicly at http://beyondplanck.science. Paper version as accepted by A&A

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• BeyondPlanck XIII. Intensity foreground sampling, degeneracies, and priors
• BeyondPlanck VII. Bayesian estimation of gain and absolute calibration for CMB experiments
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Cited by in corpus (23)

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• Cosmoglobe DR1 results. II. Constraints on isotropic cosmic birefringence from reprocessed WMAP and Planck LFI data
• BeyondPlanck I. Global Bayesian analysis of the Planck Low Frequency Instrument data
• BeyondPlanck XIII. Intensity foreground sampling, degeneracies, and priors
• Tensor-to-scalar ratio forecasts for extended LiteBIRD frequency configurations
• Full-sky Models of Galactic Microwave Emission and Polarization at Sub-arcminute Scales for the Python Sky Model
• Disentangling the Faraday rotation sky
• BeyondPlanck X. Bandpass and beam leakage corrections
• From BeyondPlanck to Cosmoglobe: Preliminary $WMAP$ $Q$-band analysis
• Cosmoglobe DR1 results. I. Improved Wilkinson Microwave Anisotropy Probe maps through Bayesian end-to-end analysis
• BeyondPlanck XI. Bayesian CMB analysis with sample-based end-to-end error propagation
• BeyondPlanck VI. Noise characterization and modelling
• QUIJOTE scientific results -- X. Spatial variations of Anomalous Microwave Emission along the Galactic plane
• BeyondPlanck XVI. Limits on Large-Scale Polarized Anomalous Microwave Emission from Planck LFI and WMAP
• BeyondPlanck X. Planck LFI frequency maps with sample-based error propagation
• BeyondPlanck VIII. Efficient Sidelobe Convolution and Correction through Spin Harmonics
• BeyondPlanck IV. On end-to-end simulations in CMB analysis -- Bayesian versus frequentist statistics
• Cosmoglobe DR1. III. First full-sky model of polarized synchrotron emission from all WMAP and Planck LFI data
• ForSE+: Simulating non-Gaussian CMB foregrounds at 3 arcminutes in a stochastic way based on a generative adversarial network
• Statistical properties of Galactic synchrotron temperature and polarization maps -- a multi-frequency comparison
• BeyondPlanck V. Minimal ADC Corrections for Planck LFI
• B-mode polarization forecasts for GreenPol
• On the computational feasibility of Bayesian end-to-end analysis of LiteBIRD simulations within Cosmoglobe