Calibration requirements for epoch of reionization 21cm signal observations  I. Effect of timecorrelated gains
Abstract
The residual gain errors add to the systematics of the radio interferometric observations. In case of the high dynamic range observations, these systematic effects dominates over the thermal noise of the observation. In this work, we investigate the effect of timecorrelated residual gain errors in the estimation of the power spectrum of the sky brightness distribution in high dynamic range observations. Particularly, we discuss a methodology to estimate the bias in the power spectrum estimator of the redshifted 21cm signal from neutral hydrogen in the presence of bright extragalactic compact sources. We find, that for the visibilitybased power spectrum estimators, particularly those use nearby baseline correlations to avoid noise bias, the bias in the power spectrum arises mainly from the time correlation in the residual gain error. The bias also depends on the baseline distribution for a particular observation. Analytical calculations show that the bias is dominant for certain types of baseline pairs used for the visibility correlation. We perform simulated observation of extragalactic compact sources in the presence of residual gain errors with the Giant Metrewave Radio Telescope like array and estimate the bias in the power spectrum. Our results indicate that in order to estimate the redshifted 21cm power spectrum, better calibration techniques, and estimator development are required.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 July 2020
 DOI:
 10.1093/mnras/staa1371
 arXiv:
 arXiv:2005.07126
 Bibcode:
 2020MNRAS.495.3683K
 Keywords:

 methods: analytical;
 methods: numerical;
 methods: statistical;
 techniques: interferometric;
 dark ages;
 reionization;
 first stars;
 Astrophysics  Instrumentation and Methods for Astrophysics;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 13 pages, 10 figures, accepted for publication in MNRAS