Estimating statistics of sky brightness using radio interferometric observations

TL;DR

This paper evaluates methods for estimating sky brightness statistics from radio interferometric data, finding that visibility-based estimators provide unbiased power spectrum estimates, especially for diffuse emission.

Contribution

It compares image-based and visibility-based estimators for sky brightness statistics, highlighting the advantages of visibility methods for unbiased power spectrum estimation.

Findings

Image-based large-scale estimates are unbiased.

Image-based power spectrum estimates are biased, especially for diffuse emission.

Visibility-based power spectrum estimator is unbiased.

Abstract

Radio interferometric data are used to estimate the sky brightness distributions in radio frequencies. Here we focus on estimators of the large-scale structure and the power spectrum of the sky brightness distribution inferred from radio interferometric observations and assess their efficacy using simulated observations of the model sky. We find that while the large-scale distribution can be unbiasedly estimated from the reconstructed image from the interferometric data, estimates of the power spectrum of the intensity fluctuations calculated from the image are generally biased. The bias is more pronounced for diffuse emission. The visibility based power spectrum estimator, however, gives an unbiased estimate of the true power spectrum. We conclude that for an observation with diffuse emission the reconstructed image can be used to estimate the large-scale distribution of the intensity, while to estimate the power spectrum, visibility based methods should be preferred.