The HERA-19 Commissioning Array: Direction-dependent Effects

Saul A. Kohn, James E. Aguirre, Paul La Plante, Tashalee S. Billings, Paul M. Chichura, Austin F. Fortino, Amy S. Igarashi, Roshan K. Benefo, Samavarti Gallardo, Zachary E. Martinot, Chuneeta D. Nunhokee, Nicholas S. Kern, Philip Bull, Adrian Liu, Paul Alexander, Zaki S. Ali, Adam P. Beardsley, Gianni Bernardi, Judd D. Bowman, Richard F. BradleyChris L. Carilli, Carina Cheng, David R. Deboer, Eloy De Lera Acedo, Joshua S. Dillon, Aaron Ewall-Wice, Gcobisa Fadana, Nicolas Fagnoni, Randall Fritz, Steven R. Furlanetto, Brian Glendenning, Bradley Greig, Jasper Grobbelaar, Bryna J. Hazelton, Jacqueline N. Hewitt, Jack Hickish, Daniel C. Jacobs, Austin Julius, Maccalvin Kariseb, Matthew Kolopanis, Telalo Lekalake, Anita Loots, David Macmahon, Lourence Malan, Cresshim Malgas, Matthys Maree, Nathan Mathison, Eunice Matsetela, Andrei Mesinger, Miguel F. Morales, Abraham R. Neben, Bojan Nikolic, Aaron R. Parsons, Nipanjana Patra, Samantha Pieterse, Jonathan C. Pober, Nima Razavi-Ghods, Jon Ringuette, James Robnett, Kathryn Rosie, Raddwine Sell, Craig Smith, Angelo Syce, Max Tegmark, Nithyanandan Thyagarajan, Peter K.G. Williams, Haoxuan Zheng

Research output: Contribution to journalArticle

Abstract

Foreground power dominates the measurements of interferometers that seek a statistical detection of highly-redshifted H i emission from the Epoch of Reionization (EoR). The chromaticity of the instrument creates a boundary in the Fourier transform of frequency (proportional to k ) between spectrally smooth emission, characteristic of the strong synchrotron foreground (the "wedge"), and the spectrally structured emission from H i in the EoR (the "EoR window"). Faraday rotation can inject spectral structure into otherwise smooth polarized foreground emission, which through instrument effects or miscalibration could possibly pollute the EoR window. For instruments pursuing a "foreground avoidance" strategy of simply measuring in the EoR window, and not attempting to model and remove foregrounds, as is the plan for the first stage of the Hydrogen Epoch of Reionization Array (HERA), characterizing the intrinsic instrument polarization response is particularly important. Using data from the HERA 19-element commissioning array, we investigate the polarization response of this new instrument in the power-spectrum domain. We perform a simple image-based calibration based on the unpolarized diffuse emission of the Global Sky Model, and show that it achieves qualitative redundancy between the nominally redundant baselines of the array and reasonable amplitude accuracy. We construct power spectra of all fully polarized coherencies in all pseudo-Stokes parameters, and discuss the achieved isolation of foreground power due to the intrinsic spectral smoothness of the foregrounds, the instrument chromaticity, and the calibration. We compare to simulations based on an unpolarized diffuse sky model and detailed electromagnetic simulations of the dish and feed, confirming that in Stokes I, the calibration does not add significant spectral structure beyond that expected from the interferometer array configuration and the modeled primary beam response. Furthermore, this calibration is stable over the 8 days of observations considered. Excess power is seen in the power spectra of the linear polarization Stokes parameters, which is not easily attributable to leakage via the primary beam, and results from some combination of residual calibration errors and actual polarized emission. Stokes V is found to be highly discrepant from the expectation of zero power, strongly pointing to the need for more accurate polarized calibration.

Original languageEnglish (US)
Article number58
JournalAstrophysical Journal
Volume882
Issue number1
DOIs
StatePublished - Sep 1 2019

Fingerprint

time measurement
hydrogen
calibration
polarization
power spectra
interferometer
sky
interferometers
parabolic reflectors
avoidance
redundancy
Fourier transform
leakage
simulation
Faraday effect
effect
linear polarization
wedges
isolation
synchrotrons

Keywords

  • cosmology: observations
  • dark ages, reionization, first stars
  • instrumentation: interferometers
  • polarization
  • techniques: interferometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Kohn, S. A., Aguirre, J. E., La Plante, P., Billings, T. S., Chichura, P. M., Fortino, A. F., ... Zheng, H. (2019). The HERA-19 Commissioning Array: Direction-dependent Effects. Astrophysical Journal, 882(1), [58]. https://doi.org/10.3847/1538-4357/ab2f72

The HERA-19 Commissioning Array : Direction-dependent Effects. / Kohn, Saul A.; Aguirre, James E.; La Plante, Paul; Billings, Tashalee S.; Chichura, Paul M.; Fortino, Austin F.; Igarashi, Amy S.; Benefo, Roshan K.; Gallardo, Samavarti; Martinot, Zachary E.; Nunhokee, Chuneeta D.; Kern, Nicholas S.; Bull, Philip; Liu, Adrian; Alexander, Paul; Ali, Zaki S.; Beardsley, Adam P.; Bernardi, Gianni; Bowman, Judd D.; Bradley, Richard F.; Carilli, Chris L.; Cheng, Carina; Deboer, David R.; Acedo, Eloy De Lera; Dillon, Joshua S.; Ewall-Wice, Aaron; Fadana, Gcobisa; Fagnoni, Nicolas; Fritz, Randall; Furlanetto, Steven R.; Glendenning, Brian; Greig, Bradley; Grobbelaar, Jasper; Hazelton, Bryna J.; Hewitt, Jacqueline N.; Hickish, Jack; Jacobs, Daniel C.; Julius, Austin; Kariseb, Maccalvin; Kolopanis, Matthew; Lekalake, Telalo; Loots, Anita; Macmahon, David; Malan, Lourence; Malgas, Cresshim; Maree, Matthys; Mathison, Nathan; Matsetela, Eunice; Mesinger, Andrei; Morales, Miguel F.; Neben, Abraham R.; Nikolic, Bojan; Parsons, Aaron R.; Patra, Nipanjana; Pieterse, Samantha; Pober, Jonathan C.; Razavi-Ghods, Nima; Ringuette, Jon; Robnett, James; Rosie, Kathryn; Sell, Raddwine; Smith, Craig; Syce, Angelo; Tegmark, Max; Thyagarajan, Nithyanandan; Williams, Peter K.G.; Zheng, Haoxuan.

In: Astrophysical Journal, Vol. 882, No. 1, 58, 01.09.2019.

Research output: Contribution to journalArticle

Kohn, SA, Aguirre, JE, La Plante, P, Billings, TS, Chichura, PM, Fortino, AF, Igarashi, AS, Benefo, RK, Gallardo, S, Martinot, ZE, Nunhokee, CD, Kern, NS, Bull, P, Liu, A, Alexander, P, Ali, ZS, Beardsley, AP, Bernardi, G, Bowman, JD, Bradley, RF, Carilli, CL, Cheng, C, Deboer, DR, Acedo, EDL, Dillon, JS, Ewall-Wice, A, Fadana, G, Fagnoni, N, Fritz, R, Furlanetto, SR, Glendenning, B, Greig, B, Grobbelaar, J, Hazelton, BJ, Hewitt, JN, Hickish, J, Jacobs, DC, Julius, A, Kariseb, M, Kolopanis, M, Lekalake, T, Loots, A, Macmahon, D, Malan, L, Malgas, C, Maree, M, Mathison, N, Matsetela, E, Mesinger, A, Morales, MF, Neben, AR, Nikolic, B, Parsons, AR, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Ringuette, J, Robnett, J, Rosie, K, Sell, R, Smith, C, Syce, A, Tegmark, M, Thyagarajan, N, Williams, PKG & Zheng, H 2019, 'The HERA-19 Commissioning Array: Direction-dependent Effects', Astrophysical Journal, vol. 882, no. 1, 58. https://doi.org/10.3847/1538-4357/ab2f72
Kohn SA, Aguirre JE, La Plante P, Billings TS, Chichura PM, Fortino AF et al. The HERA-19 Commissioning Array: Direction-dependent Effects. Astrophysical Journal. 2019 Sep 1;882(1). 58. https://doi.org/10.3847/1538-4357/ab2f72
Kohn, Saul A. ; Aguirre, James E. ; La Plante, Paul ; Billings, Tashalee S. ; Chichura, Paul M. ; Fortino, Austin F. ; Igarashi, Amy S. ; Benefo, Roshan K. ; Gallardo, Samavarti ; Martinot, Zachary E. ; Nunhokee, Chuneeta D. ; Kern, Nicholas S. ; Bull, Philip ; Liu, Adrian ; Alexander, Paul ; Ali, Zaki S. ; Beardsley, Adam P. ; Bernardi, Gianni ; Bowman, Judd D. ; Bradley, Richard F. ; Carilli, Chris L. ; Cheng, Carina ; Deboer, David R. ; Acedo, Eloy De Lera ; Dillon, Joshua S. ; Ewall-Wice, Aaron ; Fadana, Gcobisa ; Fagnoni, Nicolas ; Fritz, Randall ; Furlanetto, Steven R. ; Glendenning, Brian ; Greig, Bradley ; Grobbelaar, Jasper ; Hazelton, Bryna J. ; Hewitt, Jacqueline N. ; Hickish, Jack ; Jacobs, Daniel C. ; Julius, Austin ; Kariseb, Maccalvin ; Kolopanis, Matthew ; Lekalake, Telalo ; Loots, Anita ; Macmahon, David ; Malan, Lourence ; Malgas, Cresshim ; Maree, Matthys ; Mathison, Nathan ; Matsetela, Eunice ; Mesinger, Andrei ; Morales, Miguel F. ; Neben, Abraham R. ; Nikolic, Bojan ; Parsons, Aaron R. ; Patra, Nipanjana ; Pieterse, Samantha ; Pober, Jonathan C. ; Razavi-Ghods, Nima ; Ringuette, Jon ; Robnett, James ; Rosie, Kathryn ; Sell, Raddwine ; Smith, Craig ; Syce, Angelo ; Tegmark, Max ; Thyagarajan, Nithyanandan ; Williams, Peter K.G. ; Zheng, Haoxuan. / The HERA-19 Commissioning Array : Direction-dependent Effects. In: Astrophysical Journal. 2019 ; Vol. 882, No. 1.
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title = "The HERA-19 Commissioning Array: Direction-dependent Effects",
abstract = "Foreground power dominates the measurements of interferometers that seek a statistical detection of highly-redshifted H i emission from the Epoch of Reionization (EoR). The chromaticity of the instrument creates a boundary in the Fourier transform of frequency (proportional to k ∥) between spectrally smooth emission, characteristic of the strong synchrotron foreground (the {"}wedge{"}), and the spectrally structured emission from H i in the EoR (the {"}EoR window{"}). Faraday rotation can inject spectral structure into otherwise smooth polarized foreground emission, which through instrument effects or miscalibration could possibly pollute the EoR window. For instruments pursuing a {"}foreground avoidance{"} strategy of simply measuring in the EoR window, and not attempting to model and remove foregrounds, as is the plan for the first stage of the Hydrogen Epoch of Reionization Array (HERA), characterizing the intrinsic instrument polarization response is particularly important. Using data from the HERA 19-element commissioning array, we investigate the polarization response of this new instrument in the power-spectrum domain. We perform a simple image-based calibration based on the unpolarized diffuse emission of the Global Sky Model, and show that it achieves qualitative redundancy between the nominally redundant baselines of the array and reasonable amplitude accuracy. We construct power spectra of all fully polarized coherencies in all pseudo-Stokes parameters, and discuss the achieved isolation of foreground power due to the intrinsic spectral smoothness of the foregrounds, the instrument chromaticity, and the calibration. We compare to simulations based on an unpolarized diffuse sky model and detailed electromagnetic simulations of the dish and feed, confirming that in Stokes I, the calibration does not add significant spectral structure beyond that expected from the interferometer array configuration and the modeled primary beam response. Furthermore, this calibration is stable over the 8 days of observations considered. Excess power is seen in the power spectra of the linear polarization Stokes parameters, which is not easily attributable to leakage via the primary beam, and results from some combination of residual calibration errors and actual polarized emission. Stokes V is found to be highly discrepant from the expectation of zero power, strongly pointing to the need for more accurate polarized calibration.",
keywords = "cosmology: observations, dark ages, reionization, first stars, instrumentation: interferometers, polarization, techniques: interferometric",
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TY - JOUR

T1 - The HERA-19 Commissioning Array

T2 - Direction-dependent Effects

AU - Kohn, Saul A.

AU - Aguirre, James E.

AU - La Plante, Paul

AU - Billings, Tashalee S.

AU - Chichura, Paul M.

AU - Fortino, Austin F.

AU - Igarashi, Amy S.

AU - Benefo, Roshan K.

AU - Gallardo, Samavarti

AU - Martinot, Zachary E.

AU - Nunhokee, Chuneeta D.

AU - Kern, Nicholas S.

AU - Bull, Philip

AU - Liu, Adrian

AU - Alexander, Paul

AU - Ali, Zaki S.

AU - Beardsley, Adam P.

AU - Bernardi, Gianni

AU - Bowman, Judd D.

AU - Bradley, Richard F.

AU - Carilli, Chris L.

AU - Cheng, Carina

AU - Deboer, David R.

AU - Acedo, Eloy De Lera

AU - Dillon, Joshua S.

AU - Ewall-Wice, Aaron

AU - Fadana, Gcobisa

AU - Fagnoni, Nicolas

AU - Fritz, Randall

AU - Furlanetto, Steven R.

AU - Glendenning, Brian

AU - Greig, Bradley

AU - Grobbelaar, Jasper

AU - Hazelton, Bryna J.

AU - Hewitt, Jacqueline N.

AU - Hickish, Jack

AU - Jacobs, Daniel C.

AU - Julius, Austin

AU - Kariseb, Maccalvin

AU - Kolopanis, Matthew

AU - Lekalake, Telalo

AU - Loots, Anita

AU - Macmahon, David

AU - Malan, Lourence

AU - Malgas, Cresshim

AU - Maree, Matthys

AU - Mathison, Nathan

AU - Matsetela, Eunice

AU - Mesinger, Andrei

AU - Morales, Miguel F.

AU - Neben, Abraham R.

AU - Nikolic, Bojan

AU - Parsons, Aaron R.

AU - Patra, Nipanjana

AU - Pieterse, Samantha

AU - Pober, Jonathan C.

AU - Razavi-Ghods, Nima

AU - Ringuette, Jon

AU - Robnett, James

AU - Rosie, Kathryn

AU - Sell, Raddwine

AU - Smith, Craig

AU - Syce, Angelo

AU - Tegmark, Max

AU - Thyagarajan, Nithyanandan

AU - Williams, Peter K.G.

AU - Zheng, Haoxuan

PY - 2019/9/1

Y1 - 2019/9/1

N2 - Foreground power dominates the measurements of interferometers that seek a statistical detection of highly-redshifted H i emission from the Epoch of Reionization (EoR). The chromaticity of the instrument creates a boundary in the Fourier transform of frequency (proportional to k ∥) between spectrally smooth emission, characteristic of the strong synchrotron foreground (the "wedge"), and the spectrally structured emission from H i in the EoR (the "EoR window"). Faraday rotation can inject spectral structure into otherwise smooth polarized foreground emission, which through instrument effects or miscalibration could possibly pollute the EoR window. For instruments pursuing a "foreground avoidance" strategy of simply measuring in the EoR window, and not attempting to model and remove foregrounds, as is the plan for the first stage of the Hydrogen Epoch of Reionization Array (HERA), characterizing the intrinsic instrument polarization response is particularly important. Using data from the HERA 19-element commissioning array, we investigate the polarization response of this new instrument in the power-spectrum domain. We perform a simple image-based calibration based on the unpolarized diffuse emission of the Global Sky Model, and show that it achieves qualitative redundancy between the nominally redundant baselines of the array and reasonable amplitude accuracy. We construct power spectra of all fully polarized coherencies in all pseudo-Stokes parameters, and discuss the achieved isolation of foreground power due to the intrinsic spectral smoothness of the foregrounds, the instrument chromaticity, and the calibration. We compare to simulations based on an unpolarized diffuse sky model and detailed electromagnetic simulations of the dish and feed, confirming that in Stokes I, the calibration does not add significant spectral structure beyond that expected from the interferometer array configuration and the modeled primary beam response. Furthermore, this calibration is stable over the 8 days of observations considered. Excess power is seen in the power spectra of the linear polarization Stokes parameters, which is not easily attributable to leakage via the primary beam, and results from some combination of residual calibration errors and actual polarized emission. Stokes V is found to be highly discrepant from the expectation of zero power, strongly pointing to the need for more accurate polarized calibration.

AB - Foreground power dominates the measurements of interferometers that seek a statistical detection of highly-redshifted H i emission from the Epoch of Reionization (EoR). The chromaticity of the instrument creates a boundary in the Fourier transform of frequency (proportional to k ∥) between spectrally smooth emission, characteristic of the strong synchrotron foreground (the "wedge"), and the spectrally structured emission from H i in the EoR (the "EoR window"). Faraday rotation can inject spectral structure into otherwise smooth polarized foreground emission, which through instrument effects or miscalibration could possibly pollute the EoR window. For instruments pursuing a "foreground avoidance" strategy of simply measuring in the EoR window, and not attempting to model and remove foregrounds, as is the plan for the first stage of the Hydrogen Epoch of Reionization Array (HERA), characterizing the intrinsic instrument polarization response is particularly important. Using data from the HERA 19-element commissioning array, we investigate the polarization response of this new instrument in the power-spectrum domain. We perform a simple image-based calibration based on the unpolarized diffuse emission of the Global Sky Model, and show that it achieves qualitative redundancy between the nominally redundant baselines of the array and reasonable amplitude accuracy. We construct power spectra of all fully polarized coherencies in all pseudo-Stokes parameters, and discuss the achieved isolation of foreground power due to the intrinsic spectral smoothness of the foregrounds, the instrument chromaticity, and the calibration. We compare to simulations based on an unpolarized diffuse sky model and detailed electromagnetic simulations of the dish and feed, confirming that in Stokes I, the calibration does not add significant spectral structure beyond that expected from the interferometer array configuration and the modeled primary beam response. Furthermore, this calibration is stable over the 8 days of observations considered. Excess power is seen in the power spectra of the linear polarization Stokes parameters, which is not easily attributable to leakage via the primary beam, and results from some combination of residual calibration errors and actual polarized emission. Stokes V is found to be highly discrepant from the expectation of zero power, strongly pointing to the need for more accurate polarized calibration.

KW - cosmology: observations

KW - dark ages, reionization, first stars

KW - instrumentation: interferometers

KW - polarization

KW - techniques: interferometric

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