The Effect of Interplanetary Scintillation on Epoch of Reionisation Power Spectra

TL;DR

This paper investigates how interplanetary scintillation affects the measurements of the Epoch of Reionisation power spectra, finding that under typical conditions, its impact is minimal and does not significantly hinder cosmological signal detection.

Contribution

The study models the IPS power spectrum in EoR measurement space and assesses its impact, demonstrating that IPS leakage is generally negligible for standard observations.

Findings

IPS has a distinct spectral structure from foregrounds.

Under typical conditions, IPS impact on EoR measurements is minimal.

Leakage from IPS into the EoR window is negligible unless observing deep within foreground regions.

Abstract

Interplanetary Scintillation (IPS) induces intensity fluctuations in small angular size astronomical radio sources via the distortive effects of spatially and temporally varying electron density associated with outflows from the Sun. These radio sources are a potential foreground contaminant signal for redshifted HI emission from the Epoch of Reionisation (EoR) because they yield time-dependent flux density variations in bright extragalactic point sources. Contamination from foreground continuum sources complicates efforts to discriminate the cosmological signal from other sources in the sky. In IPS, at large angles from the Sun applicable to EoR observations, weak scattering induces spatially and temporally correlated fluctuations in the measured flux density of sources in the field, potentially affecting the detectability of the EoR signal by inducing non-static variations in the signal strength. In this work, we explore the impact of interplanetary weak scintillation on EoR power spectrum measurements, accounting for the instrumental spatial and temporal sampling. We use published power spectra of electron density fluctuations and parameters of EoR experiments to derive the IPS power spectrum in the wavenumber phase space of EoR power spectrum measurements. The contrast of IPS power to expected cosmological power is used as a metric to assess the impact of IPS. We show that IPS has a different spectral structure to power from foregrounds alone, but the additional leakage into the EoR observation parameter space is negligible under typical IPS conditions, unless data are used from deep within the foreground contamination region.