BEAM-FORMING ERRORS IN MURCHISON WIDEFIELD ARRAY PHASED ARRAY ANTENNAS AND THEIR EFFECTS ON EPOCH OF REIONIZATION SCIENCE

Journal Article · Sun Mar 20 00:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/820/1/44· OSTI ID:22521408

Neben, Abraham R.; Hewitt, Jacqueline N.; Dillon, Joshua S.; Goeke, R.; Morgan, E. ^[1]; Bradley, Richard F. ^[2]; Bernardi, G. ^[3]; Bowman, J. D. ^[4]; Briggs, F. ^[5]; Cappallo, R. J.; Corey, B. E.; Lonsdale, C. J.; McWhirter, S. R. ^[6]; Deshpande, A. A. ^[7]; Greenhill, L. J. ^[8]; Hazelton, B. J.; Morales, M. F. ^[9]; Johnston-Hollitt, M. ^[10]; Kaplan, D. L. ^[11]; Mitchell, D. A. ^[12] ; others, and

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1. Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
2. Dept. of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA, 22904 (United States)
3. Square Kilometre Array South Africa (SKA SA), Cape Town 7405 (South Africa)
4. School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States)
5. Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia)
6. MIT Haystack Observatory, Westford, MA 01886 (United States)
7. Raman Research Institute, Bangalore 560080 (India)
8. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
9. Department of Physics, University of Washington, Seattle, WA 98195 (United States)
10. School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140 (New Zealand)
11. Department of Physics, University of Wisconsin–Milwaukee, Milwaukee, WI 53201 (United States)
12. CSIRO Astronomy and Space Science (CASS), P.O. Box 76, Epping, NSW 1710 (Australia)

Accurate antenna beam models are critical for radio observations aiming to isolate the redshifted 21 cm spectral line emission from the Dark Ages and the Epoch of Reionization (EOR) and unlock the scientific potential of 21 cm cosmology. Past work has focused on characterizing mean antenna beam models using either satellite signals or astronomical sources as calibrators, but antenna-to-antenna variation due to imperfect instrumentation has remained unexplored. We characterize this variation for the Murchison Widefield Array (MWA) through laboratory measurements and simulations, finding typical deviations of the order of ±10%–20% near the edges of the main lobe and in the sidelobes. We consider the ramifications of these results for image- and power spectrum-based science. In particular, we simulate visibilities measured by a 100 m baseline and find that using an otherwise perfect foreground model, unmodeled beam-forming errors severely limit foreground subtraction accuracy within the region of Fourier space contaminated by foreground emission (the “wedge”). This region likely contains much of the cosmological signal, and accessing it will require measurement of per-antenna beam patterns. However, unmodeled beam-forming errors do not contaminate the Fourier space region expected to be free of foreground contamination (the “EOR window”), showing that foreground avoidance remains a viable strategy.

• OSTI ID: 22521408
• Journal Information: Astrophysical Journal, Vol. 820, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCURACY
ANTENNAS
AVOIDANCE
BEAMS
COSMOLOGY
EMISSION
ERRORS
IMAGES
INTERFEROMETRY
POTENTIALS
RED SHIFT
SATELLITES
SIGNALS
SPACE
STARS
VARIATIONS
VISIBILITY