Antenna beam characterisation for the global 21cm experiment LEDA and its impact on signal model parameter reconstruction

Abstract

Cosmic Dawn, the onset of star formation in the early universe, can in principle be studied via the 21cm transition of neutral hydrogen, for which a sky-averaged absorption signal, redshifted to MHz frequencies, is predicted to be {\it O}(10-100)\,mK. Detection requires separation of the 21cm signal from bright chromatic foreground emission due to Galactic structure, and the characterisation of how it couples to instrumental response. In this work, we present characterisation of antenna gain patterns for the Large-aperture Experiment to detect the Dark Ages (LEDA) via simulations, assessing the effects of the antenna ground-plane geometries used, and measured soil properties. We then investigate the impact of beam pattern uncertainties on the reconstruction of a Gaussian absorption feature. Assuming the pattern is known and correcting for the chromaticity of the instrument, the foregrounds can be modelled with a log-polynomial, and the 21cm signal identified with high accuracy. However, uncertainties on the soil properties lead to \textperthousand\ changes in the chromaticity that can bias the signal recovery. The bias can be up to a factor of two in amplitude and up to few \% in the frequency location. These effects do not appear to be mitigated by larger ground planes, conversely gain patterns with larger ground planes exhibit more complex frequency structure, significantly compromising the parameter reconstruction. Our results, consistent with findings from other antenna design studies, emphasise the importance of chromatic response and suggest caution in assuming log-polynomial foreground models in global signal experiments.

arXiv commentAccepted for publication in MNRAS

References in corpus (61)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• Multimodal nested sampling: an efficient and robust alternative to MCMC methods for astronomical data analysis
• 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
• Possible interaction between baryons and dark-matter particles revealed by the first stars
• Insights on Dark Matter from Hydrogen during Cosmic Dawn
• Detecting the Earliest Galaxies Through Two New Sources of 21cm Fluctuations
• 21 cm fluctuations from inhomogeneous X-ray heating before reionization
• Enhanced global signal of neutral hydrogen due to excess radiation at cosmic dawn
• Concerns about Modelling of the EDGES Data
• Signatures of X-rays in the early Universe
• A lower limit of dz > 0.06 for the duration of the reionization epoch
• The observable signature of late heating of the Universe during cosmic reionization
• 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
• What does the first highly-redshifted 21-cm detection tell us about early galaxies?
• Design and characterization of the Large-Aperture Experiment to Detect the Dark Age (LEDA) radiometer systems
• The 21-cm signature of the first stars during the Lyman-Werner feedback era
• The Global 21-cm Signal in the Context of the High-z Galaxy Luminosity Function
• Reviving Millicharged Dark Matter for 21-cm Cosmology
• Testing for calibration systematics in the EDGES low-band data using Bayesian model selection
• 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
• The redshifted 21-cm signal in the EDGES low-band spectrum
• Bayesian constraints on the global 21-cm signal from the Cosmic Dawn
• Results from EDGES High-Band: I. Constraints on Phenomenological Models for the Global $21$ cm Signal
• The Evolution of 21-cm Structure (EOS): public, large-scale simulations of Cosmic Dawn and Reionization
• Decoding the X-ray Properties of Pre-Reionization Era Sources
• Foreground Model and Antenna Calibration Errors in the Measurement of the Sky-Averaged λ21 cm Signal at z~20
• The Radio Sky at Meter Wavelengths: m-Mode Analysis Imaging with the Owens Valley Long Wavelength Array
• High-redshift radio galaxies: a potential new source of 21-cm fluctuations
• Chromatic effects in the 21 cm global signal from the cosmic dawn
• 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
• Characterization of a Low-Frequency Radio Astronomy Prototype Array in Western Australia
• An MCMC approach to extracting the global 21-cm signal during the cosmic dawn from sky-averaged radio observations
• Interpreting the Global 21-cm Signal from High Redshifts. II. Parameter Estimation for Models of Galaxy Formation
• A wide-band, active antenna system for long wavelength radio astronomy
• Spectral Index of the Diffuse Radio Background Between 50 and 100 MHz
• maxsmooth: Rapid Maximally Smooth Function Fitting With Applications in Global 21-cm Cosmology
• SARAS 3 CD/EoR Radiometer: Design and Performance of the Receiver
• Limits on Foreground Subtraction from Chromatic Beam Effects in Global Redshifted 21 cm Measurements
• A 21-cm power spectrum at 48 MHz, using the Owens Valley Long Wavelength Array
• Measuring the Cosmological 21 cm Monopole with an Interferometer
• 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
• The 21-cm BAO signature of enriched low-mass galaxies during cosmic reionization
• Validation of EDGES Low-Band Antenna Beam Model
• On the contamination of the global 21~cm signal from polarized foregrounds
• GMOSS: All-sky model of spectral radio brightness based on physical components and associated radiative processes
• Design and Commissioning of the LWA1 Radio Telescope
• Informing antenna design for sky-averaged 21-cm experiments using a simulated Bayesian data analysis pipeline
• Spectral index of the Galactic foreground emission in the 50-87 MHz range
• Global 21-cm signal extraction from foreground and instrumental effects IV: Accounting for realistic instrument uncertainties and their overlap with foreground and signal models
• Absolute Calibration of Diffuse Radio Surveys at 45 and 150 MHz
• Shot noise and scatter in the star formation efficiency as a source of 21-cm fluctuations
• A Floating Octave Bandwidth Cone-Disc Antenna for Detection of Cosmic Dawn

Cited by in corpus (19)

• Mapper of the IGM spin temperature: instrument overview
• PRATUSH experiment concept and design overview
• A Bayesian approach to modelling spectrometer data chromaticity corrected using beam factors -- I. Mathematical formalism
• A General Bayesian Framework to Account for Foreground Map Errors in Global 21-cm Experiments
• Simulating the Detection of the Global 21 cm Signal with MIST for Different Models of the Soil and Beam Directivity
• The effects of the antenna power pattern uncertainty within a global 21 cm experiment
• Receiver design for the REACH global 21-cm signal experiment
• RHINO: A large horn antenna for detecting the 21cm global signal
• Direction-dependent effects on global 21-cm detection
• STARFIRE: An algorithm for estimating radio frequency interference in orbits around Earth
• A Bayesian approach to modelling spectrometer data chromaticity corrected using beam factors -- II. Model priors and posterior odds
• Forecast measurement of the 21 cm global spectrum from Lunar orbit with the Vari-Zeroth-Order Polynomial (VZOP) method
• Detecting Cosmic 21 cm Global Signal Using an Improved Polynomial Fitting Algorithm
• Estimating Soil Electrical Parameters in the Canadian High Arctic from Impedance Measurements of the MIST Antenna Above the Surface
• Probing Non-Minimal Dark Sectors via the 21 cm Line at Cosmic Dawn
• Sensitivity toward dark matter annihilation imprints on 21-cm signal with SKA-Low: A convolutional neural network approach
• The impact of lunar topography on the 21-cm power spectrum for grid-based arrays : Insights for the Dark-ages EXplorer (DEX)
• Using the antenna impedance to estimate soil electrical parameters for the MIST global 21-cm experiment
• An SBC-based controller and processor for the laboratory model of PRATUSH Digital Receiver