Foreground Subtraction in Intensity Mapping with the SKA

TL;DR

This paper reviews and tests foreground subtraction techniques for 21cm intensity mapping with SKA, demonstrating that the cosmological signal, including Baryon Acoustic Oscillations, can be recovered despite foreground contamination.

Contribution

It introduces a simulation-based evaluation of foreground subtraction methods for SKA intensity mapping, highlighting their effectiveness in preserving key cosmological features.

Findings

Angular power spectrum is recovered within statistical errors.

Foreground subtraction does not affect the Baryon Acoustic Oscillation scale.

Residuals from ICA are manageable for cosmological analysis.

Abstract

21cm intensity mapping experiments aim to observe the diffuse neutral hydrogen (HI) distribution on large scales which traces the Cosmic structure. The Square Kilometre Array (SKA) will have the capacity to measure the 21cm signal over a large fraction of the sky. However, the redshifted 21cm signal in the respective frequencies is faint compared to the Galactic foregrounds produced by synchrotron and free-free electron emission. In this article, we review selected foreground subtraction methods suggested to effectively separate the 21cm signal from the foregrounds with intensity mapping simulations or data. We simulate an intensity mapping experiment feasible with SKA phase 1 including extragalactic and Galactic foregrounds. We give an example of the residuals of the foreground subtraction with a independent component analysis and show that the angular power spectrum is recovered within the statistical errors on most scales. Additionally, the scale of the Baryon Acoustic Oscillations is shown to be unaffected by foreground subtraction.