Constraining a Model of the Radio Sky Below 6 MHz Using the Parker Solar Probe/FIELDS Instrument in Preparation for Upcoming Lunar-based Experiments

Abstract

We present a Bayesian analysis of data from the FIELDS instrument on board the Parker Solar Probe (PSP) spacecraft with the aim of constraining low frequency ($\lesssim$ 6 MHz) sky in preparation for several upcoming lunar-based experiments. We utilize data recorded during PSP's ``coning roll'' maneuvers, in which the axis of the spacecraft is pointed 45${}^{\circ }$ off of the Sun. The spacecraft then rotates about a line between the Sun and the spacecraft with a period of 24 minutes. We reduce the data into two formats: roll-averaged, in which the spectra are averaged over the roll, and phase-binned, in which the spectra are binned according to the phase of the roll. We construct a forward model of the FIELDS observations that includes numerical simulations of the antenna beam, an analytic emissivity function of the galaxy, and estimates of the absorption due to free electrons. Fitting 5 parameters, we find that the roll-averaged data can be fit well by this model and we obtain posterior parameter constraints that are in general agreement with previous estimates. The model is not, however, able to fit the phase-binned data well, likely due to limitations such as the lack of non-smooth emission structure at both small and large scales, enforced symmetry between the northern and southern galactic hemispheres, and large uncertainties in the free electron density. This suggests that significant improvement in the low frequency sky model is needed in order to fully and accurately represent the sky at frequencies below 6 MHz.

arXiv comment18 pages, 10 figures, 5 tables. Under review in the Astrophysical Journal

References in corpus (24)

• 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
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• A New Electron Density Model for Estimation of Pulsar and FRB Distances
• Importance Nested Sampling and the MultiNest Algorithm
• 21-cm cosmology
• A model of diffuse Galactic Radio Emission from 10 MHz to 100 GHz
• Reionization and Cosmology with 21 cm Fluctuations
• The Vertical Structure of Warm Ionised Gas in the Milky Way
• Data Analysis for Precision 21 cm Cosmology
• An Improved Model of Diffuse Galactic Radio Emission from 10 MHz to 5 THz
• All-sky Galactic radiation at 45 MHz and spectral index between 45 and 408 MHz
• A General Bayesian Framework for Foreground Modelling and Chromaticity Correction for Global 21cm Experiments
• Global 21cm signal experiments: A designer's guide
• Is there concordance within the concordance $\Lambda$CDM model?
• Quantifying Ionospheric Effects on Global 21-cm Observations
• Quantifying Tensions between CMB and Distance Datasets in Models with Free Curvature or Lensing Amplitude
• 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
• 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
• An Ultra-long Wavelength Sky Model with Absorption Effect
• A Bayesian Calibration Framework for EDGES
• Bayesian evidence-driven diagnosis of instrumental systematics for sky-averaged 21-cm cosmology experiments

Cited by in corpus (1)

• An Instrument Error Budget for Space-Based Absolute Flux Measurements of the Sky Synchrotron Spectrum Below 20 MHz