Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/6330
Title: Foregrounds in wide-field redshifted 21 cm power spectra
Authors: Thyagarajan, Nithyanandan
Paul, Sourabh
Prabhu, T.
Udaya shankar, N.
Sethi, S.K.
Srivani, K.S.
Subrahmanyan, Ravi
+25 Co-authors
Issue Date: 1-May-2015
Publisher: IOP Sciences for The American Astronomical Society
Citation: Astrophysical Journal, 2015, Vol. 804, p 14
Abstract: Detection of 21 cm emission of H i from the epoch of reionization, at redshifts $z\gt 6$, is limited primarily by foreground emission. We investigate the signatures of wide-field measurements and an all-sky foreground model using the delay spectrum technique that maps the measurements to foreground object locations through signal delays between antenna pairs. We demonstrate interferometric measurements are inherently sensitive to all scales, including the largest angular scales, owing to the nature of wide-field measurements. These wide-field effects are generic to all observations but antenna shapes impact their amplitudes substantially. A dish-shaped antenna yields the most desirable features from a foreground contamination viewpoint, relative to a dipole or a phased array. Comparing data from recent Murchison Widefield Array observations, we demonstrate that the foreground signatures that have the largest impact on the H i signal arise from power received far away from the primary field of view. We identify diffuse emission near the horizon as a significant contributing factor, even on wide antenna spacings that usually represent structures on small scales. For signals entering through the primary field of view, compact emission dominates the foreground contamination. These two mechanisms imprint a characteristic pitchfork signature on the "foreground wedge" in Fourier delay space. Based on these results, we propose that selective down-weighting of data based on antenna spacing and time can mitigate foreground contamination substantially by a factor of ~100 with negligible loss of sensitivity.
Description: Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI: http://hdl.handle.net/2289/6330
ISSN: 0004-637X
1538-4357-(Online)
Alternative Location: http://adsabs.harvard.edu/abs/2015ApJ...804...14T
http://arxiv.org/abs/1502.07596
http://dx.doi.org/10.1088/0004-637X/804/1/14
Copyright: 2015, The American Astronomical Society.
Appears in Collections:Research Papers (A&A)

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