Foregrounds in wide-field Redshifted 21 cm power spectra

Nithyanandan Thyagarajan, Daniel Jacobs, Judd Bowman, N. Barry, A. P. Beardsley, G. Bernardi, F. Briggs, R. J. Cappallo, P. Carroll, B. E. Corey, A. De Oliveira-Costa, Joshua S. Dillon, D. Emrich, A. Ewall-Wice, L. Feng, R. Goeke, L. J. Greenhill, B. J. Hazelton, J. N. Hewitt, N. Hurley-Walker & 44 others M. Johnston-Hollitt, D. L. Kaplan, J. C. Kasper, Han Seek Kim, P. Kittiwisit, E. Kratzenberg, E. Lenc, J. Line, A. Loeb, C. J. Lonsdale, M. J. Lynch, 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, A. E E Rogers, A. Roshi, N. Udaya Shankar, Shiv K. Sethi, K. S. Srivani, R. Subrahmanyan, I. S. Sullivan, M. Tegmark, S. J. Tingay, C. M. Trott, M. Waterson, R. B. Wayth, R. L. Webster, A. R. Whitney, A. Williams, C. L. Williams, C. Wu, J. S B Wyithe

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

Detection of 21 cm emission of H i from the epoch of reionization, at redshifts , 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.

Original languageEnglish (US)
Article number14
JournalAstrophysical Journal
Volume804
Issue number1
DOIs
StatePublished - May 1 2015

Fingerprint

antenna
power spectra
antennas
contamination
signatures
field of view
spacing
parabolic reflectors
phased arrays
wedges
horizon
sky
time measurement
dipoles
sensitivity

Keywords

  • cosmology: observations
  • dark ages, reionization, first stars
  • large-scale structure of universe
  • methods: statistical
  • radio continuum: galaxies
  • techniques: interferometric

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Thyagarajan, N., Jacobs, D., Bowman, J., Barry, N., Beardsley, A. P., Bernardi, G., ... Wyithe, J. S. B. (2015). Foregrounds in wide-field Redshifted 21 cm power spectra. Astrophysical Journal, 804(1), [14]. https://doi.org/10.1088/0004-637X/804/1/14

Foregrounds in wide-field Redshifted 21 cm power spectra. / Thyagarajan, Nithyanandan; Jacobs, Daniel; Bowman, Judd; Barry, N.; Beardsley, A. P.; Bernardi, G.; Briggs, F.; Cappallo, R. J.; Carroll, P.; Corey, B. E.; Oliveira-Costa, A. De; Dillon, Joshua S.; Emrich, D.; Ewall-Wice, A.; Feng, L.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Hewitt, J. N.; Hurley-Walker, N.; Johnston-Hollitt, M.; Kaplan, D. L.; Kasper, J. C.; Kim, Han Seek; Kittiwisit, P.; Kratzenberg, E.; Lenc, E.; Line, J.; Loeb, A.; Lonsdale, C. J.; Lynch, M. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Neben, A. R.; Oberoi, D.; Offringa, A. R.; Ord, S. M.; Paul, Sourabh; Pindor, B.; Pober, J. C.; Prabu, T.; Procopio, P.; Riding, J.; Rogers, A. E E; Roshi, A.; Shankar, N. Udaya; Sethi, Shiv K.; Srivani, K. S.; Subrahmanyan, R.; Sullivan, I. S.; Tegmark, M.; Tingay, S. J.; Trott, C. M.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.; Wu, C.; Wyithe, J. S B.

In: Astrophysical Journal, Vol. 804, No. 1, 14, 01.05.2015.

Research output: Contribution to journalArticle

Thyagarajan, N, Jacobs, D, Bowman, J, Barry, N, Beardsley, AP, Bernardi, G, Briggs, F, Cappallo, RJ, Carroll, P, Corey, BE, Oliveira-Costa, AD, Dillon, JS, Emrich, D, Ewall-Wice, A, Feng, L, Goeke, R, Greenhill, LJ, Hazelton, BJ, Hewitt, JN, Hurley-Walker, N, Johnston-Hollitt, M, Kaplan, DL, Kasper, JC, Kim, HS, Kittiwisit, P, Kratzenberg, E, Lenc, E, Line, J, Loeb, A, Lonsdale, CJ, Lynch, MJ, McKinley, B, McWhirter, SR, Mitchell, DA, Morales, MF, Morgan, E, Neben, AR, Oberoi, D, Offringa, AR, Ord, SM, Paul, S, Pindor, B, Pober, JC, Prabu, T, Procopio, P, Riding, J, Rogers, AEE, Roshi, A, Shankar, NU, Sethi, SK, Srivani, KS, Subrahmanyan, R, Sullivan, IS, Tegmark, M, Tingay, SJ, Trott, CM, Waterson, M, Wayth, RB, Webster, RL, Whitney, AR, Williams, A, Williams, CL, Wu, C & Wyithe, JSB 2015, 'Foregrounds in wide-field Redshifted 21 cm power spectra', Astrophysical Journal, vol. 804, no. 1, 14. https://doi.org/10.1088/0004-637X/804/1/14
Thyagarajan, Nithyanandan ; Jacobs, Daniel ; Bowman, Judd ; Barry, N. ; Beardsley, A. P. ; Bernardi, G. ; Briggs, F. ; Cappallo, R. J. ; Carroll, P. ; Corey, B. E. ; Oliveira-Costa, A. De ; Dillon, Joshua S. ; Emrich, D. ; Ewall-Wice, A. ; Feng, L. ; Goeke, R. ; Greenhill, L. J. ; Hazelton, B. J. ; Hewitt, J. N. ; Hurley-Walker, N. ; Johnston-Hollitt, M. ; Kaplan, D. L. ; Kasper, J. C. ; Kim, Han Seek ; Kittiwisit, P. ; Kratzenberg, E. ; Lenc, E. ; Line, J. ; Loeb, A. ; Lonsdale, C. J. ; Lynch, M. J. ; McKinley, B. ; McWhirter, S. R. ; Mitchell, D. A. ; Morales, M. F. ; Morgan, E. ; Neben, A. R. ; Oberoi, D. ; Offringa, A. R. ; Ord, S. M. ; Paul, Sourabh ; Pindor, B. ; Pober, J. C. ; Prabu, T. ; Procopio, P. ; Riding, J. ; Rogers, A. E E ; Roshi, A. ; Shankar, N. Udaya ; Sethi, Shiv K. ; Srivani, K. S. ; Subrahmanyan, R. ; Sullivan, I. S. ; Tegmark, M. ; Tingay, S. J. ; Trott, C. M. ; Waterson, M. ; Wayth, R. B. ; Webster, R. L. ; Whitney, A. R. ; Williams, A. ; Williams, C. L. ; Wu, C. ; Wyithe, J. S B. / Foregrounds in wide-field Redshifted 21 cm power spectra. In: Astrophysical Journal. 2015 ; Vol. 804, No. 1.
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AU - Thyagarajan, Nithyanandan

AU - Jacobs, Daniel

AU - Bowman, Judd

AU - Barry, N.

AU - Beardsley, A. P.

AU - Bernardi, G.

AU - Briggs, F.

AU - Cappallo, R. J.

AU - Carroll, P.

AU - Corey, B. E.

AU - Oliveira-Costa, A. De

AU - Dillon, Joshua S.

AU - Emrich, D.

AU - Ewall-Wice, A.

AU - Feng, L.

AU - Goeke, R.

AU - Greenhill, L. J.

AU - Hazelton, B. J.

AU - Hewitt, J. N.

AU - Hurley-Walker, N.

AU - Johnston-Hollitt, M.

AU - Kaplan, D. L.

AU - Kasper, J. C.

AU - Kim, Han Seek

AU - Kittiwisit, P.

AU - Kratzenberg, E.

AU - Lenc, E.

AU - Line, J.

AU - Loeb, A.

AU - Lonsdale, C. J.

AU - Lynch, M. J.

AU - McKinley, B.

AU - McWhirter, S. R.

AU - Mitchell, D. A.

AU - Morales, M. F.

AU - Morgan, E.

AU - Neben, A. R.

AU - Oberoi, D.

AU - Offringa, A. R.

AU - Ord, S. M.

AU - Paul, Sourabh

AU - Pindor, B.

AU - Pober, J. C.

AU - Prabu, T.

AU - Procopio, P.

AU - Riding, J.

AU - Rogers, A. E E

AU - Roshi, A.

AU - Shankar, N. Udaya

AU - Sethi, Shiv K.

AU - Srivani, K. S.

AU - Subrahmanyan, R.

AU - Sullivan, I. S.

AU - Tegmark, M.

AU - Tingay, S. J.

AU - Trott, C. M.

AU - Waterson, M.

AU - Wayth, R. B.

AU - Webster, R. L.

AU - Whitney, A. R.

AU - Williams, A.

AU - Williams, C. L.

AU - Wu, C.

AU - Wyithe, J. S B

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N2 - Detection of 21 cm emission of H i from the epoch of reionization, at redshifts , 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.

AB - Detection of 21 cm emission of H i from the epoch of reionization, at redshifts , 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.

KW - cosmology: observations

KW - dark ages, reionization, first stars

KW - large-scale structure of universe

KW - methods: statistical

KW - radio continuum: galaxies

KW - techniques: interferometric

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