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    Beam-forming errors in Murchison Widefield array phased array antennas and their effects on epoch of reionization science

    239388_239388.pdf (8.820Mb)
    Access Status
    Open access
    Authors
    Neben, A.
    Hewitt, J.
    Bradley, R.
    Dillon, J.
    Bernardi, G.
    Bowman, J.
    Briggs, F.
    Cappallo, R.
    Corey, B.
    Deshpande, A.
    Goeke, R.
    Greenhill, L.
    Hazelton, B.
    Johnston-Hollitt, M.
    Kaplan, D.
    Lonsdale, C.
    McWhirter, S.
    Mitchell, D.
    Morales, M.
    Morgan, E.
    Oberoi, D.
    Ord, S.
    Prabu, T.
    Shankar, N.
    Srivani, K.
    Subrahmanyan, R.
    Tingay, Steven
    Wayth, Randall
    Webster, R.
    Williams, A.
    Williams, C.
    Date
    2016
    Type
    Journal Article
    
    Metadata
    Show full item record
    Citation
    Neben, A. and Hewitt, J. and Bradley, R. and Dillon, J. and Bernardi, G. and Bowman, J. and Briggs, F. et al. 2016. Beam-forming errors in Murchison Widefield array phased array antennas and their effects on epoch of reionization science. Astrophysical Journal. 820 (1): Article ID 44.
    Source Title
    Astrophysical Journal
    DOI
    10.3847/0004-637X/820/1/44
    ISSN
    0004-637X
    School
    Curtin Institute of Radio Astronomy (Physics)
    URI
    http://hdl.handle.net/20.500.11937/38311
    Collection
    • Curtin Research Publications
    Abstract

    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.

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