Correlation-based Beam Calibration of 21 cm Intensity Mapping

Foreground removal presents a significant obstacle in both current and forthcoming intensity-mapping surveys. While numerous techniques have been developed that show promise in simulated data sets, their efficacy often diminishes when they are applied to real-world data. A primary issue is the frequency-dependent variations in the instrumental response. In this paper, we propose a novel approach utilizing the internal cross correlation among different frequencies to calibrate the beam's frequency fluctuations. Using a simulated data set that incorporates frequency-dependent random fluctuations into the beam model, we illustrate that our method can achieve considerable improvements over traditional techniques. Our results represent a step forward in enhancing the precision and reliability of foreground removal in intensity-mapping surveys.