Absolute Calibration Strategies for the Hydrogen Epoch of Reionization Array and Their Impact on the 21 cm Power Spectrum

Kern, Nicholas S.; Dillon, Joshua S.; Parsons, Aaron; Carilli, Christopher L.; Bernardi, G.; Abdurashidova, Zara; Aguirre, James E.; Alexander, Paul; Ali, Zaki S.; Balfour, Yanga; Beardsley, Adam P.; Billings, Tashalee S.; Bowman, Judd D.; Bradley, Richard F.; Bull, Philip; Burba, Jacob; Carey, S. H.; Cheng, Carina; DeBoer, David R.; Dexter, Matt; Acedo, Eloy de Lera; Ely, John; Ewall‐Wice, Aaron; Fagnoni, Nicolas; Fritz, Randall; Furlanetto, Steve R.; Gale‐Sides, Kingsley; Glendenning, Brian; Gorthi, Deepthi; Greig, Bradley; Grobbelaar, Jasper; Halday, Ziyaad; Hazelton, B. J.; Hewitt, Jacqueline N.; Hickish, J.; Jacobs, Daniel; Julius, Austin; Kerrigan, Joshua; Kittiwisit, Piyanat; Kohn, Saul A.; Kolopanis, Matthew; Lanman, Adam; Plante, Paul La; Lekalake, Telalo; Liu, Adrian; MacMahon, David H. E.; Malan, Lourence; Malgas, Cresshim; Maree, Matthys; Martinot, Zachary E.; Matsetela, Eunice; Mesinger, Andrei; Molewa, Mathakane; Morales, M. F.; Mosiane, Tshegofalang; Murray, Steven; Neben, Abraham R.; Nikolic, Bojan; Nunhokee, Chuneeta D.; Patra, Nipanjana; Pieterse, Samantha; Pober, Jonathan C.; Razavi-Ghods, N.; Ringuette, Jon; Robnett, James; Rosie, Kathryn; Sims, Peter; Smith, Craig; Syce, Angelo; Thyagarajan, Nithyanandan; Williams, Peter K. G.; Zheng, Haoxuan

doi:10.3847/1538-4357/ab67bc

Cited by 48 publications

(83 citation statements)

References 89 publications

(143 reference statements)

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“…This effect has been considered by a number of authors, including Byrne et al (2019), Li et al (2019), Barry et al (2016), van Weeren et al (2016), and Ewall-Wice et al (2017. Most recently, Kern et al (2020) show that the unmodeled spectral structure leads to a peak in the amplitudes in the delay transform at around ∼200 nanosec, implying potential contamination of the measured H I 21 cm power spectrum using the delay spectrum approach at low wavenumber k∼0.1 Mpc −1 . Fortunately, delay spectrum searches for H I 21 cm emission have thus far relied on analyses at wavenumbers, k0.2 Mpc −1 (Parsons et al 2014).…”

Section: Discussionmentioning

confidence: 99%

“…How will the unmodeled extra spectral structure affect the HERA search for the H I 21 cm signal from cosmic reionization? This question has been considered in Kern et al (2020) and , which we briefly summarize.…”

Section: Discussionmentioning

confidence: 99%

“…The data for imaging have been flagged using the standard HERA procedures (Kerrigan et al 2019). The data have been calibrated using a hybrid process of initial sky-based delay calibration, then redundant baseline calibration, then a skybased calibration procedure to determine the missing parameters inherent in the redundant baseline calibration process and to determine the absolute gain scale and bandpass (Dillon et al 2017;Kern et al 2020).…”

Section: Hydrogen Epoch Of Reionization Arraymentioning

confidence: 99%

“…Self-calibration in the case of Fornax A was required due to the dynamic range issues posed by the large flux density of Fornax A. The standard bandpass calibration process for HERA is weighted toward sources near the pointing center (=zenith), in the calibration fields (Kern et al 2020). Fornax A, being well down in the primary beam, has a significant residual spectral shape imposed by the primary beam shape as a function of frequency.…”

Section: Hydrogen Epoch Of Reionization Arraymentioning

confidence: 99%

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Imaging and Modeling Data from the Hydrogen Epoch of Reionization Array

Carilli

Thyagarajan

Kent

et al. 2020

ApJS

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We analyze data from the Hydrogen Epoch of Reionization Array (HERA). This is the third in a series of papers on the closure phase delay spectrum technique designed to detect the H I 21 cm emission from cosmic reionization. We present the details of the data and models employed in the power spectral analysis and discuss limitations to the process. We compare images and visibility spectra made with HERA data to parallel quantities generated from sky models based on the Galactic and Extra-Galactic All-Sky MWA (GLEAM) survey, incorporating the HERA telescope model. We find reasonable agreement between images made from HERA data with those generated from the models, down to the confusion level. For the visibility spectra, there is broad agreement between model and data across the full band of ∼80 MHz. However, models with only GLEAM sources do not reproduce a roughly sinusoidal spectral structure at the tens of percent level seen in the observed visibility spectra on scales of ∼10 MHz on 29 m baselines. We find that this structure is likely due to diffuse Galactic emission, predominantly the Galactic plane, filling the far sidelobes of the antenna primary beam. We show that our current knowledge of the frequency dependence of the diffuse sky radio emission, and the primary beam at large zenith angles, is inadequate to provide an accurate reproduction of the diffuse structure in the models. We discuss some implications arising due to this missing structure in the models, in terms of calibration, and in the search for the H I 21 cm signal, as well as possible mitigation techniques.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Hydrogen Epoch Of Reionization Arraymentioning

confidence: 99%

Section: Hydrogen Epoch Of Reionization Arraymentioning

confidence: 99%

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Imaging and Modeling Data from the Hydrogen Epoch of Reionization Array

Carilli

Thyagarajan

Kent

et al. 2020

ApJS

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“…Although the principles and limitations of each calibration method are reasonably well understood, the actual performance of these techniques will be affected by realistic constraints, such as algorithm implementations, array configuration, sky model accuracy, and data contamination from interference. Recent analysis with the HERA telescope shows the potential for redundant calibration to provide some degree of information beyond sky calibration, as well as its value as a data quality metric (Kern et al 2020;Dillon et al 2020). Li et al (2018) used the compact array of Phase II of the MWA (Wayth et al 2018;Beardsley et al 2019), which has both large numbers of redundant baselines and a relatively complete sampling of Fourier space (i.e.…”

Section: Introductionmentioning

confidence: 99%

The impact of tandem redundant/sky-based calibration in MWA Phase II data analysis

Zhang

Pober

et al. 2020

Publ. Astron. Soc. Aust.

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Precise instrumental calibration is of crucial importance to 21-cm cosmology experiments. The Murchison Widefield Array’s (MWA) Phase II compact configuration offers us opportunities for both redundant calibration and sky-based calibration algorithms; using the two in tandem is a potential approach to mitigate calibration errors caused by inaccurate sky models. The MWA Epoch of Reionization (EoR) experiment targets three patches of the sky (dubbed EoR0, EoR1, and EoR2) with deep observations. Previous work in Li et al. (2018) and (2019) studied the effect of tandem calibration on the EoR0 field and found that it yielded no significant improvement in the power spectrum (PS) over sky-based calibration alone. In this work, we apply similar techniques to the EoR1 field and find a distinct result: the improvements in the PS from tandem calibration are significant. To understand this result, we analyse both the calibration solutions themselves and the effects on the PS over three nights of EoR1 observations. We conclude that the presence of the bright radio galaxy Fornax A in EoR1 degrades the performance of sky-based calibration, which in turn enables redundant calibration to have a larger impact. These results suggest that redundant calibration can indeed mitigate some level of model incompleteness error.

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