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25 April 2024

» arxiv » 1506.6150

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Confirmation of Wide-Field Signatures in Redshifted 21 cm Power Spectra
Nithyanandan Thyagarajan ; Daniel C. Jacobs ; Judd D. Bowman ; N. Barry ; A. P. Beardsley ; G. Bernardi ; F. Briggs ; R. J. Cappallo ; P. Carroll ; A. A. Deshpande ; A. de Oliveira-Costa ; Joshua S. Dillon ; A. Ewall-Wice ; L. Feng ; L. J. Greenhill ; B. J. Hazelton ; L. Hernquist ; J. N. Hewitt ; N. Hurley-Walker ; M. Johnston-Hollitt ; D. L. Kaplan ; Han-Seek Kim ; P. Kittiwisit ; E. Lenc ; J. Line ; A. Loeb ; C. J. Lonsdale ; B. McKinley ; S. R. McWhirter ; D. A. Mitchell ; M. F. Morales ; E. Morgan ; A. R. Neben ; D. Oberoi ; A. R. Offringa ; S. M. Ord ; Sourabh Paul ; B. Pindor ; J. C. Pober ; T. Prabu ; P. Procopio ; J. Riding ; N. Udaya Shankar ; Shiv K. Sethi ; K. S. Srivani ; R. Subrahmanyan ; I. S. Sullivan ; M. Tegmark ; S. J. Tingay ; C. M. Trott ; R. B. Wayth ; R. L. Webster ; A. Williams ; C. L. Williams ; J. S. B. Wyithe ;
Date:	19 Jun 2015
Abstract:	We confirm our recent prediction of the "pitchfork" foreground signature in power spectra of high-redshift 21 cm measurements, wherein the interferometer is sensitive to large-scale structure on all baselines. This is due to the inherent response of a wide-field instrument and is characterized by enhanced power from foreground emission in Fourier modes adjacent to those considered to be most sensitive to the cosmological HI signal. In our recent paper, many signatures from the simulation which predicted this feature were validated against Murchison Widefield Array (MWA) data but this key pitchfork signature was close to the noise level. In this paper, we improve the data sensitivity through coherent averaging of 12 independent snapshots with identical instrument settings, and provide the first confirmation of the prediction with a signal-noise ratio > 10. This wide-field effect can be mitigated by careful antenna designs that suppress sensitivity near the horizon. Simple models for antenna apertures proposed for future instruments such as the Hydrogen Epoch of Reionization Array and the Square Kilometre Array indicate they should suppress foreground leakage from the pitchfork by ~40 dB relative to the MWA, and significantly increase the likelihood of cosmological signal detection in these critical Fourier modes in the three-dimensional power spectrum.
Source:	arXiv, 1506.6150
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