The Fundamental Multi-Baseline Mode-Mixing Foreground in 21 cm EoR Observations

TL;DR

This paper identifies a new multi-baseline mode-mixing effect in 21 cm EoR observations that contaminates the EoR window, posing a significant challenge for foreground removal.

Contribution

It introduces and characterizes a novel multi-baseline mode-mixing effect that dominates foreground contamination in EoR measurements.

Findings

Multi-baseline mode-mixing dominates in simulations.

Contaminates the EoR window in Fourier space.

Impacts foreground mitigation strategies.

Abstract

The primary challenge for experiments measuring the neutral hydrogen power spectrum from the Epoch of Reionization (EoR) are mode-mixing effects where foregrounds from very bright astrophysical sources interact with the instrument to contaminate the EoR signal. In this paper we identify a new type of mode-mixing that occurs when measurements from non-identical baselines are combined for increased power spectrum sensitivity. This multi-baseline effect dominates the mode-mixing power in our simulations and can contaminate the EoR window, an area in Fourier space previously identified to be relatively free of foreground power.