The impact of extragalactic foregrounds on internal delensing of CMB B-mode polarization

Abstract

The search for primordial $B$-mode polarization of the CMB is limited by the sample variance of $B$-modes produced at later times by gravitational lensing. Constraints can be improved by `delensing': using some proxy of the matter distribution to partially remove the lensing-induced $B$-modes. Current and soon-upcoming experiments will infer a matter map -- at least in part -- from the temperature anisotropies of the CMB. These reconstructions are contaminated by extragalactic foregrounds: radio-emitting galaxies, the cosmic infrared background, or the Sunyaev--Zel'dovich effects. Using the Websky simulations, we show that the foregrounds add spurious power to the angular auto-spectrum of delensed $B$-modes via non-Gaussian higher-point functions, biasing constraints on the tensor-to-scalar ratio, $r$. We consider an idealized experiment similar to the Simons Observatory, with no Galactic or atmospheric foregrounds. After removing point sources detectable at 143 GHz and reconstructing lensing from CMB temperature modes $l<3500$ using a Hu-Okamoto quadratic estimator (QE), we infer a value of $r$ that is $1.5\sigma$ higher than the true $r=0$. Reconstructing instead from a minimum-variance ILC map only exacerbates the problem, bringing the bias above $3\sigma$. When the $TT$ estimator is co-added with other QEs or with external matter tracers, new couplings ensue which partially cancel the diluted bias from $TT$. We provide a simple and effective prescription to model these effects. In addition, we demonstrate that the point-source-hardened or shear-only QEs can not only mitigate the biases to acceptable levels, but also lead to lower power than the Hu-Okamoto QE after delensing. Thus, temperature-based reconstructions remain powerful tools in the quest to measure $r$.

arXiv comment23 pages plus appendix and bibliography. 17 figures. Very minor changes to match version published in PRD

References in corpus (79)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• Planck 2018 results. I. Overview and the cosmological legacy of Planck
• The Simons Observatory: Science goals and forecasts
• Weak Gravitational Lensing of the CMB
• A Joint Analysis of BICEP2/Keck Array and Planck Data
• Signature of Gravity Waves in Polarization of the Microwave Background
• BICEP / Keck XIII: Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/Keck Observations through the 2018 Observing Season
• A Probe of Primordial Gravity Waves and Vorticity
• The Cosmic Infrared Background: Measurements and Implications
• Planck 2018 results. VIII. Gravitational lensing
• Mass Reconstruction with CMB Polarization
• A high resolution foreground cleaned CMB map from WMAP
• Gravitational Lensing Effect on Cosmic Microwave Background Polarization
• A unified pseudo-$C_{\ell }$ framework
• The Quest for B Modes from Inflationary Gravitational Waves
• Detection of Gravitational Lensing in the Cosmic Microwave Background
• Reconstruction of lensing from the cosmic microwave background polarization
• Detection of B-mode Polarization in the Cosmic Microwave Background with Data from the South Pole Telescope
• A limit on the detectability of the energy scale of inflation
• CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
• A measurement of gravitational lensing of the microwave background using South Pole Telescope data
• Gravitational lensing as a contaminant of the gravity wave signal in CMB
• On the Cluster Physics of Sunyaev-Zel'dovich Surveys II: Deconstructing the Thermal SZ Power Spectrum
• CMB and SZ effect separation with Constrained Internal Linear Combinations
• The shape of the CMB lensing bispectrum
• Using the kinematic Sunyaev-Zeldovich effect to determine the peculiar velocities of clusters of galaxies
• The Atacama Cosmology Telescope: likelihood for small-scale CMB data
• Delensing CMB Polarization with External Datasets
• Analysis of CMB polarization on an incomplete sky
• HerMES: Cosmic Infrared Background Anisotropies and the Clustering of Dusty Star-Forming Galaxies
• Lensed CMB power spectra from all-sky correlation functions
• CMB temperature lensing power reconstruction
• Planck 2015 results. XXIII. The thermal Sunyaev-Zeldovich effect--cosmic infrared background correlation
• Extragalactic Foreground Contamination in Temperature-based CMB Lens Reconstruction
• CMB Lensing Power Spectrum Biases from Galaxies and Clusters using High-angular Resolution Temperature Maps
• Impact of post-Born lensing on the CMB
• Delensing the CMB with the Cosmic Infrared Background
• The Websky Extragalactic CMB Simulations
• Maximum a posteriori CMB lensing reconstruction
• A Measurement of the Cosmic Microwave Background Lensing Potential and Power Spectrum from 500 deg${}^2$ of SPTpol Temperature and Polarization Data
• The mass-Peak Patch algorithm for fast generation of deep all-sky dark matter halo catalogues and its N-Body validation
• Improved Models for Cosmic Infrared Background Anisotropies: New Constraints on the IR Galaxy Population
• Mitigating Foreground Biases in CMB Lensing Reconstruction Using Cleaned Gradients
• Inflation versus Cyclic Predictions for Spectral Tilt
• A Measurement of the Correlation of Galaxy Surveys with CMB Lensing Convergence Maps from the South Pole Telescope
• The Atacama Cosmology Telescope: Lensing of CMB Temperature and Polarization Derived from Cosmic Infrared Background Cross-Correlation
• Foreground-immune CMB lensing with shear-only reconstruction
• Dark Energy Survey Year 3 Results: Galaxy clustering and systematics treatment for lens galaxy samples
• Internal delensing of Planck CMB temperature and polarization
• Lower bias, lower noise CMB lensing with foreground-hardened estimators
• Quadratic estimators for CMB weak lensing
• CMB Polarization B-mode Delensing with SPTpol and Herschel
• Bayesian delensing delight: sampling-based inference of the primordial CMB and gravitational lensing
• Characterization of foreground emission at degree angular scale for CMB B-modes observations. Thermal Dust and Synchrotron signal from Planck and WMAP data
• Bias to CMB Lensing Reconstruction from Temperature Anisotropies due to Large-Scale Galaxy Motions
• Full-sky CMB lensing reconstruction in presence of sky-cuts
• Lensing Reconstruction in Post-Born Cosmic Microwave Background Weak Lensing
• Multitracer CMB delensing maps from Planck and WISE data
• A Demonstration of Improved Constraints on Primordial Gravitational Waves with Delensing
• Weak Lensing of the CMB by Large-Scale Structure
• Impact of polarised extragalactic sources on the measurement of CMB B-mode anisotropies
• The Simons Observatory: Constraining inflationary gravitational waves with multi-tracer B-mode delensing
• Internal delensing of Cosmic Microwave Background polarization B-modes with the POLARBEAR experiment
• Partially Constrained Internal Linear Combination: a method for low-noise CMB foreground mitigation
• CMB internal delensing with general optimal estimator for higher-order correlations
• $B$-mode forecast of CMB-Bh$\overline{a}$rat
• Impact of internal-delensing biases on searches for primordial B-modes of CMB polarisation
• Limitations of CMB B-mode template delensing
• Optimal multifrequency weighting for CMB lensing
• Comparison of delensing methodologies and assessment of the delensing capabilities of future experiments
• Simulated catalogs and maps of radio galaxies at millimeter wavelengths in Websky
• Optimal constraints on primordial gravitational waves from the lensed CMB
• Delensing the CMB with the cosmic infrared background: the impact of foregrounds
• Revised estimates of CMB $B$-mode polarization induced by patchy reionization
• Mitigating Foreground Bias to the CMB Lensing Power Spectrum for a CMB-HD Survey
• Delensing Degree-Scale $B$-Mode Polarization with High-Redshift Line Intensity Mapping
• Lensed CMB power spectrum biases from masking extragalactic sources

Cited by in corpus (11)

• CMB-S4: Iterative Internal Delensing and $r$ Constraints
• Foreground-immune CMB lensing reconstruction with polarization
• LiteBIRD Science Goals and Forecasts: Improving Sensitivity to Inflationary Gravitational Waves with Multitracer Delensing
• CMB lensing with shear-only reconstruction on the full sky
• Subtracting the kinetic Sunyaev-Zeldovich effect from the cosmic microwave background with surveys of large-scale structure
• New probe of inflationary gravitational waves: cross-correlations of lensed primary CMB B-modes with large-scale structure
• A halo model of extragalactic contamination to CMB lensing, delensing, and cross-correlations
• Stage IV CMB forecasts for warm inflation
• Delensing for Precision Cosmology: Optimizing Future CMB B-mode Surveys to Constrain r
• LiteBIRD science goals and forecasts: improved full-sky reconstruction of the gravitational lensing potential through the combination of Planck and LiteBIRD data
• Delensing CMB B-modes using galaxy surveys: the effect of galaxy bias and matter clustering non-linearities