Impact of Calibration and Position Errors on Astrophysical Parameters of the HI 21cm Signal

TL;DR

This study evaluates how calibration and position errors affect the extraction of astrophysical parameters from the redshifted 21-cm signal during the Epoch of Reionization and Cosmic Dawn, using simulations and neural network-based inference.

Contribution

It introduces a framework combining neural networks and Bayesian methods to directly infer astrophysical parameters without explicit calibration corrections, and assesses error tolerances for SKA-Low observations.

Findings

Gain calibration error tolerance is 0.001%.

Sky model position errors above 0.048 arcseconds hinder signal detection.

Framework effectively estimates parameters despite systematics.

Abstract

The Epoch of Reionization (EoR) and Cosmic Dawn (CD) are pivotal stages during the first billion years of the universe, exerting a significant influence on the development of cosmic structure. The detection of the redshifted 21-cm signal from these epochs is challenging due to the dominance of significantly stronger astrophysical foregrounds and the presence of systematics. This work used the 21cm E2E (end to end) pipeline, followed by simulation methodology described \cite{2022Mazumder} to conduct synthetic observations of a simulated sky model that includes both the redshifted 21-cm signal and foregrounds. A framework was constructed using Artificial Neural Networks (ANN) and Bayesian techniques to directly deduce astrophysical parameters from the measured power spectrum. This approach eliminates the need for explicit telescope layout effects correction in interferometric arrays such as SKA-Low. The present work investigates the impact of gain calibration errors and sky model position errors on the recovery of the redshifted 21-cm power spectrum for the SKA-Low AA$^{\ast}$ array configuration. We assessed the effects of these inaccuracies on the deduced astrophysical parameters and established acceptable tolerance levels. Based on our results, the gain calibration error tolerance for ideal signal detection is 0.001 \%. However, if the sky model position errors exceed 0.048 arcseconds, the remaining foregrounds would obscure the target signal.