Overcoming real-world obstacles in 21 cm power spectrum estimation: A method demonstration and results from early Murchison Widefield Array data

Joshua S. Dillon, Adrian Liu, Christopher L. Williams, Jacqueline N. Hewitt, Max Tegmark, Edward H. Morgan, Alan M. Levine, Miguel F. Morales, Steven J. Tingay, Gianni Bernardi, Judd D. Bowman, Frank H. Briggs, Roger C. Cappallo, David Emrich, Daniel A. Mitchell, Divya Oberoi, Thiagaraj Prabu, Randall Wayth, and Rachel L. Webster
Phys. Rev. D 89, 023002 – Published 15 January 2014

Abstract

We present techniques for bridging the gap between idealized inverse covariance weighted quadratic estimation of 21 cm power spectra and the real-world challenges presented universally by interferometric observation. By carefully evaluating various estimators and adapting our techniques for large but incomplete data sets, we develop a robust power spectrum estimation framework that preserves the so-called "Epoch of Reionization (EoR) window" and keeps track of estimator errors and covariances. We apply our method to observations from the 32-tile prototype of the Murchinson Widefield Array to demonstrate the importance of a judicious analysis technique. Lastly, we apply our method to investigate the dependence of the clean EoR window on frequency—especially the frequency dependence of the so-called “wedge" feature—and establish upper limits on the power spectrum from z=6.2 to z=11.7. Our lowest limit is Δ(k)<0.3 Kelvin at 95% confidence at a comoving scale k=0.046Mpc1 and z=9.5.

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  • Received 25 April 2013

DOI:https://doi.org/10.1103/PhysRevD.89.023002

© 2014 American Physical Society

Authors & Affiliations

Joshua S. Dillon1,2,*, Adrian Liu1,2,3,†, Christopher L. Williams1,2, Jacqueline N. Hewitt1,2, Max Tegmark1,2, Edward H. Morgan1, Alan M. Levine1, Miguel F. Morales4, Steven J. Tingay5,6, Gianni Bernardi7, Judd D. Bowman8, Frank H. Briggs6,9, Roger C. Cappallo10, David Emrich5, Daniel A. Mitchell6,11, Divya Oberoi10,12, Thiagaraj Prabu13, Randall Wayth5,6, and Rachel L. Webster6,11

  • 1MIT Kavli Institute, Massachusetts Institute of Technology, Cambridge, 02139 Massachusetts, USA
  • 2Department of Physics, Massachusetts Institute of Technology, Cambridge, 02139 Massachusetts, USA
  • 3Department of Astronomy and Berkeley Center for Cosmological Physics, Berkeley, 94720 California, USA
  • 4Department of Physics, University of Washington, Seattle, 98195 Washington, USA
  • 5International Centre for Radio Astronomy Research, Curtin University, Perth, 6009 Western Australia, Australia
  • 6ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), Australia
  • 7Harvard-Smithsonian Center for Astrophysics, Harvard University, Cambridge, 02138 Massachusetts, USA
  • 8School of Space and Earth Exploration, Arizona State University, Tempe, 85287 Arizona, USA
  • 9Research School of Astronomy and Astrophysics, The Australian National University, 2611 Canberra, Australia
  • 10MIT-Haystack Observatory, Westford, 01886 Massachusetts, USA
  • 11School of Physics, The University of Melbourne, 3010 Melbourne, Australia
  • 12National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, 411007 Pune, India
  • 13Raman Research Institute, Bangalore 560080, India

  • *jsdillon@mit.edu
  • acliu@berkeley.edu

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Vol. 89, Iss. 2 — 15 January 2014

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