Mitigating antenna gain errors with HyFoReS in CHIME simulations

TL;DR

HyFoReS is a novel algorithm that effectively reduces antenna gain-related foreground contamination in 21-cm intensity mapping simulations, improving the detection prospects for the hydrogen auto-power spectrum.

Contribution

This study demonstrates the application of HyFoReS to CHIME-like simulations, showing its ability to mitigate gain errors and foreground bias in polarized visibilities.

Findings

HyFoReS reduces foreground bias below thermal noise levels for small perturbations.

The algorithm can decrease residual foreground bias by up to three orders of magnitude with complex gain errors.

Noise bias and second-order effects are current limitations but do not prevent HyFoReS from suppressing gain-induced leakage.

Abstract

Hybrid Foreground Residual Subtraction (HyFoReS) is a new family of algorithms designed to remove systematics-induced foreground contamination for 21-cm intensity mapping data. Previously, the algorithm was shown to be effective in mitigating beam perturbations in sky maps from the Canadian Hydrogen Intensity Mapping Experiment (CHIME). In this study, we apply HyFoReS to CHIME simulations and test the algorithm's ability to mitigate antenna gain-type systematics in polarized visibilities. Simulating a two-cylinder telescope similar to the CHIME pathfinder, we find that HyFoReS reduces foreground bias caused by bandpass perturbations to a level below the thermal noise, provided that the RMS value of the perturbations is on the order of $10^{-4}$ or lower. When tested with complex antenna-dependent gain errors, HyFoReS can reduce residual foreground bias in the power spectrum by up to three orders of magnitude. While noise bias and second-order perturbations are currently the limiting factors for the algorithm, we have demonstrated that HyFoReS can suppress gain-induced foreground leakage in polarized data from 21-cm telescopes, aiding in the detection of the 21-cm auto-power spectrum for hydrogen intensity mapping experiments.