Subtraction of Bright Point Sources from Synthesis Images of the Epoch of Reionization

TL;DR

This paper presents a new method combining matched filters and iterative centroiding to subtract bright point sources from low-frequency radio images, significantly improving the dynamic range for Epoch of Reionization studies.

Contribution

The paper introduces a novel technique for subtracting bright point sources in EoR observations, addressing frequency-dependent sidelobe issues that hinder foreground removal.

Findings

Improves dynamic range of EOR maps by 2-3 orders of magnitude.

Effectively locates and characterizes point sources amidst diffuse background.

Enhances foreground subtraction accuracy for 21cm cosmology.

Abstract

Bright point sources associated with extragalactic AGN and radio galaxies are an important foreground for low frequency radio experiments aimed at detecting the redshifted 21cm emission from neutral hydrogen during the epoch of reionization. The frequency dependence of the synthesized beam implies that the sidelobes of these sources will move across the field of view as a function of observing frequency, hence frustrating line-of-sight foreground subtraction techniques. We describe a method for subtracting these point sources from dirty maps produced by an instrument such as the MWA. This technique combines matched filters with an iterative centroiding scheme to locate and characterize point sources in the presence of a diffuse background. Simulations show that this technique can improve the dynamic range of EOR maps by 2-3 orders of magnitude.