A General Bayesian Framework to Account for Foreground Map Errors in Global 21-cm Experiments

Abstract

Measurement of the global 21-cm signal during Cosmic Dawn (CD) and the Epoch of Reionization (EoR) is made difficult by bright foreground emission which is 2-5 orders of magnitude larger than the expected signal. Fitting for a physics-motivated parametric forward model of the data within a Bayesian framework provides a robust means to separate the signal from the foregrounds, given sufficient information about the instrument and sky. It has previously been demonstrated that, within such a modelling framework, a foreground model of sufficient fidelity can be generated by dividing the sky into $N$ regions and scaling a base map assuming a distinct uniform spectral index in each region. Using the Radio Experiment for the Analysis of Cosmic Hydrogen (REACH) as our fiducial instrument, we show that, if unaccounted-for, amplitude errors in low-frequency radio maps used for our base map model will prevent recovery of the 21-cm signal within this framework, and that the level of bias in the recovered 21-cm signal is proportional to the amplitude and the correlation length of the base-map errors in the region. We introduce an updated foreground model that is capable of accounting for these measurement errors by fitting for a monopole offset and a set of spatially-dependent scale factors describing the ratio of the true and model sky temperatures, with the size of the set determined by Bayesian evidence-based model comparison. We show that our model is flexible enough to account for multiple foreground error scenarios allowing the 21-cm sky-averaged signal to be detected without bias from simulated observations with a smooth conical log spiral antenna.

18 pages, 13 figures

References in corpus (66)

• Planck 2015 results. XIII. Cosmological parameters
• LOFAR: The LOw-Frequency ARray
• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• An absorption profile centred at 78 megahertz in the sky-averaged spectrum
• 21-cm cosmology
• Hydrogen Epoch of Reionization Array (HERA)
• Possible interaction between baryons and dark-matter particles revealed by the first stars
• PolyChord: nested sampling for cosmology
• PolyChord: next-generation nested sampling
• A model of diffuse Galactic Radio Emission from 10 MHz to 100 GHz
• Reionization and Cosmology with 21 cm Fluctuations
• The Precision Array for Probing the Epoch of Reionization: 8 Station Results
• The Murchison Widefield Array: Design Overview
• A simulation calibrated limit on the HI power spectrum from the GMRT Epoch of Reionization experiment
• The Global 21 Centimeter Background from High Redshifts
• Concerns about Modelling of the EDGES Data
• Data Analysis for Precision 21 cm Cosmology
• Modeling the Radio Background from the First Black Holes at Cosmic Dawn: Implications for the 21 cm Absorption Amplitude
• An Improved Model of Diffuse Galactic Radio Emission from 10 MHz to 5 THz
• Charting the Parameter Space of the Global 21-cm Signal
• Signature of Excess Radio Background in the 21-cm Global Signal and Power Spectrum
• Foregrounds for observations of the cosmological 21 cm line: I. First Westerbork measurements of Galactic emission at 150 MHz in a low latitude field
• Foreground Contamination in Interferometric Measurements of the Redshifted 21 cm Power Spectrum
• Design and characterization of the Large-Aperture Experiment to Detect the Dark Age (LEDA) radiometer systems
• Testing for calibration systematics in the EDGES low-band data using Bayesian model selection
• All-sky Galactic radiation at 45 MHz and spectral index between 45 and 408 MHz
• BIGHORNS - Broadband Instrument for Global HydrOgen ReioNisation Signal
• A Ground Plane Artifact that Induces an Absorption Profile in Averaged Spectra from Global 21-cm Measurements - with Possible Application to EDGES
• An Improved Method for 21cm Foreground Removal
• The redshifted 21-cm signal in the EDGES low-band spectrum
• First results on the Epoch of Reionization from First Light with SARAS 2
• Bayesian constraints on the global 21-cm signal from the Cosmic Dawn
• Toward Empirical Constraints on the Global Redshifted 21 cm Brightness Temperature During the Epoch of Reionization
• Foregrounds for observations of the cosmological 21 cm line: II. Westerbork observations of the fields around 3C196 and the North Celestial Pole
• The REACH radiometer for detecting the 21-cm hydrogen signal from redshift 7.5 to 28
• Non-parametric foreground subtraction for 21cm epoch of reionization experiments
• The LWA1 Low Frequency Sky Survey
• Will point sources spoil 21 cm tomography?
• De-contamination of cosmological 21-cm maps
• The subtlety of Ly-a photons: changing the expected range of the 21-cm signal
• A General Bayesian Framework for Foreground Modelling and Chromaticity Correction for Global 21cm Experiments
• Global 21cm signal experiments: A designer's guide
• An MCMC approach to extracting the global 21-cm signal during the cosmic dawn from sky-averaged radio observations
• Constraining cosmology and ionization history with combined 21 cm power spectrum and global signal measurements
• maxsmooth: Rapid Maximally Smooth Function Fitting With Applications in Global 21-cm Cosmology
• SARAS measurement of the Radio Background at long wavelengths
• Quantifying Ionospheric Effects on Global 21-cm Observations
• Can Early Dark Energy Explain EDGES?
• Formulating and critically examining the assumptions of global 21-cm signal analyses: How to avoid the false troughs that can appear in single spectrum fits
• Global 21-cm signal extraction from foreground and instrumental effects I: Pattern recognition framework for separation using training sets
• Global 21-cm Signal Extraction from Foreground and Instrumental Effects II: Efficient and Self-Consistent Technique for Constraining Nonlinear Signal Models
• Antenna beam characterisation for the global 21cm experiment LEDA and its impact on signal model parameter reconstruction
• Informing antenna design for sky-averaged 21-cm experiments using a simulated Bayesian data analysis pipeline
• Use of Time Dependent Data in Bayesian Global 21cm Foreground and Signal Modelling
• Global 21-cm signal extraction from foreground and instrumental effects III: Utilizing drift-scan time dependence and full Stokes measurements
• Bayesian noise wave calibration for 21-cm global experiments
• A Bayesian Calibration Framework for EDGES
• Absolute Calibration of Diffuse Radio Surveys at 45 and 150 MHz
• Global 21-cm signal extraction from foreground and instrumental effects IV: Accounting for realistic instrument uncertainties and their overlap with foreground and signal models
• A Bayesian approach to modelling spectrometer data chromaticity corrected using beam factors -- I. Mathematical formalism
• Systematic uncertainties in models of the cosmic dawn
• A Bayesian approach to high fidelity interferometric calibration II: demonstration with simulated data
• Joint constraints on reionization: a framework for combining the global 21cm signal and the kinetic Sunyaev-Zel'dovich effect
• Bayesian evidence-driven diagnosis of instrumental systematics for sky-averaged 21-cm cosmology experiments
• Extracting the Global Signal from 21-cm Fluctuations: the Multi-Tracer Approach
• Bayesian evidence-driven likelihood selection for sky-averaged 21-cm signal extraction

Cited by in corpus (10)

• Simulation-Based Inference of the sky-averaged 21-cm signal from CD-EoR with REACH
• Impact of extragalactic point sources on the low-frequency sky spectrum and cosmic dawn global 21-cm measurements
• A Differentiable, End-to-End Forward Model for 21 cm Cosmology: Estimating the Foreground, Instrument, and Signal Joint Posterior
• Bayesian evidence for flux scale errors in Galactic synchrotron maps
• A Bayesian approach to modelling spectrometer data chromaticity corrected using beam factors -- II. Model priors and posterior odds
• A general Bayesian model-validation framework based on null-test evidence ratios, with an example application to global 21-cm cosmology
• Quantifying the Impact of Lunar and Planetary Occultation on Experimental Global 21 cm Cosmology
• Bayesian recalibration of flux scale factors in diffuse radio maps using low-resolution absolute radiometers
• Recovering 21cm Monopole Signals Without Smoothness
• Optimizing Foreground Modelling for Global 21cm Cosmology with GPU-Accelerated Nested Sampling