Comparing Redundant and Sky Model Based Interferometric Calibration: A First Look with Phase II of the MWA
Abstract
Interferometric arrays seeking to measure the 21 cm signal from the Epoch of Reionization must contend with overwhelmingly bright emission from foreground sources. Accurate recovery of the 21 cm signal will require precise calibration of the array, and several new avenues for calibration have been pursued in recent years, including methods using redundancy in the antenna configuration. The newly upgraded Phase II of Murchison Widefield Array (MWA) is the first interferometer that has large numbers of redundant baselines while retaining good instantaneous UV-coverage. This array therefore provides a unique opportunity to compare redundant calibration with sky-model based algorithms. In this paper, we present the first results from comparing both calibration approaches with MWA Phase II observations. For redundant calibration, we use the package OMNICAL, and produce sky-based calibration solutions with the analysis package Fast Holographic Deconvolution (FHD). There are three principal results. (1) We report the success of OMNICAL on observations of ORBComm satellites, showing substantial agreement between redundant visibility measurements after calibration. (2) We directly compare OMNICAL calibration solutions with those from FHD, and demonstrate these two different calibration schemes give extremely similar results. (3) We explore improved calibration by combining OMNICAL and FHD. We evaluate these combined methods using power spectrum techniques developed for EoR analysis and find evidence for marginal improvements mitigating artifacts in the power spectrum. These results are likely limited by signal-to-noise in the six hours of data used, but suggest future directions for combining these two calibration schemes.
Keywords
Cite
@article{arxiv.1807.05312,
title = {Comparing Redundant and Sky Model Based Interferometric Calibration: A First Look with Phase II of the MWA},
author = {W. Li and J. C. Pober and B. J. Hazelton and N. Barry and M. F. Morales and I. Sullivan and A. R. Parsons and Z. S. Ali and J. S. Dillon and A. P. Beardsley and J. D. Bowman and F. Briggs and R. Byrne and P. Carroll and B. Crosse and D. Emrich and A. Ewall-Wice and L. Feng and T. M. O. Franzen and J. N. Hewitt and L. Horsley and D. C. Jacobs and M. Johnston-Hollitt and C. Jordan and R. C. Joseph and D. L. Kaplan and D. Kenney and H. Kim and P. Kittiwisit and A. Lanman and J. Line and B. McKinley and D. A. Mitchell and S. Murray and A. Neben and A. R. Offringa and D. Pallot and S. Paul and B. Pindor and P. Procopio and M. Rahimi and J. Riding and S. K. Sethi and N. Udaya Shankar and K. Steele and R. Subrahmanian and M. Tegmark and N. Thyagarajan and S. J. Tingay and C. Trott and M. Walker and R. B. Wayth and R. L. Webster and A. Williams and C. Wu and S. Wyithe},
journal= {arXiv preprint arXiv:1807.05312},
year = {2018}
}
Comments
20 pages, 11 figures. Accepted to ApJ