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The Impact of Beam Variations on Power Spectrum Estimation for 21 cm Cosmology. I. Simulations of Foreground Contamination for HERA

Kim, Honggeun and Nhan, Bang D. and Hewitt, Jacqueline N. and Kern, Nicholas S. and Dillon, Joshua S. and de Lera Acedo, Eloy and Dynes, Scott B. C. and Mahesh, Nivedita and Fagnoni, Nicolas and DeBoer, David R. (2022) The Impact of Beam Variations on Power Spectrum Estimation for 21 cm Cosmology. I. Simulations of Foreground Contamination for HERA. Astrophysical Journal, 941 (2). Art. No. 207. ISSN 0004-637X. doi:10.3847/1538-4357/ac9eaf.

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Detecting cosmological signals from the Epoch of Reionization (EoR) requires high-precision calibration to isolate the cosmological signals from foreground emission. In radio interferometry, the perturbed primary beams of antenna elements can disrupt the precise calibration, which results in the contamination of the foreground-free region, or the EoR window, in the cylindrically averaged power spectrum. For the Hydrogen Epoch of Reionization Array (HERA), we simulate and characterize the perturbed primary beams that are induced by feed motions, such as axial, lateral, and tilting motions, above the 14 m dish. To understand the effect of the perturbed beams, visibility measurements are modeled with two different foreground components, point sources and diffuse sources, and we find that different feed motions present a different reaction to each type of sky source. HERA’s redundant baseline calibration in the presence of nonredundant antenna beams due to feed motions introduces chromatic errors in the gain solutions, producing foreground power leakage into the EoR window. The observed leakage from the vertical feed motions comes predominantly from point sources around the zenith. Furthermore, the observed leakage from the horizontal and tilting feed motions comes predominantly from the diffuse components near the horizon. Mitigation of the chromatic gain errors will be necessary for robust detections of the EoR signals with minimal foreground bias, and this will be discussed in a subsequent paper.

Item Type:Article
Related URLs:
URLURL TypeDescription
Kim, Honggeun0000-0001-5421-8927
Nhan, Bang D.0000-0001-5122-9997
Hewitt, Jacqueline N.0000-0002-4117-570X
Kern, Nicholas S.0000-0002-8211-1892
Dillon, Joshua S.0000-0003-3336-9958
de Lera Acedo, Eloy0000-0001-8530-6989
Dynes, Scott B. C.0000-0001-7010-0937
Mahesh, Nivedita0000-0003-2560-8023
Fagnoni, Nicolas0000-0001-5300-3166
DeBoer, David R.0000-0003-3197-2294
Additional Information:This material is based upon work supported by the National Science Foundation, under grant Nos. 1636646 and 1836019, and institutional support from the HERA collaboration partners. This research is funded in part by the Gordon and Betty Moore Foundation, through grant GBMF5212 to the Massachusetts Institute of Technology. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. B.D.N. is a Jansky Fellow of the National Radio Astronomy Observatory. N.S.K. gratefully acknowledges support from the MIT Pappalardo fellowship.
Funding AgencyGrant Number
HERA partner institutionsUNSPECIFIED
Gordon and Betty Moore FoundationGBMF5212
Jansky FellowshipUNSPECIFIED
Massachusetts Institute of Technology (MIT)UNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20230117-372591200.34
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:118839
Deposited By: Research Services Depository
Deposited On:10 Feb 2023 21:49
Last Modified:10 Feb 2023 21:49

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