A Bayesian approach to high fidelity interferometric calibration − II: demonstration with simulated data

Sims, Peter; Pober, Jonathan C.; Sievers, Jonathan

doi:10.1093/mnras/stac1749

Cited by 8 publications

(1 citation statement)

References 77 publications

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“…Lowlevel spectral errors in calibration introduce spectral structure into the foreground signal, preventing effective foreground removal. In recent years, this problem has inspired a proliferation of precision bandpass calibration methods (Mitchell et al 2008;Yatawatta et al 2009;Kazemi et al 2011;Sullivan et al 2012;Kazemi & Yatawatta 2013;Salvini & Wijnholds 2014;Sievers 2017;Dillon et al 2020;Kern et al 2020;Sob et al 2020;Byrne et al 2021b;Ewall-Wice et al 2022;Sims et al 2022aSims et al , 2022b. Nevertheless, precision calibration approaches generally require exquisite prior knowledge of the sky signal and instrumental response, and calibration precision remains a principal limitation of 21 cm cosmology analyses.…”

Section: Introductionmentioning

confidence: 99%

Delay-weighted Calibration: Precision Calibration for 21 cm Cosmology with Resilience to Sky Model Error

Byrne

2023

ApJ

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One of the principal challenges of 21 cm cosmology experiments is overcoming calibration error. Established calibration approaches in the field require an exquisitely accurate sky model, and low-level sky model errors introduce calibration errors that corrupt the cosmological signal. We present a novel calibration approach called delay-weighted calibration, or DWCal, which enables precise calibration even in the presence of sky model error. Sky model error does not affect all power spectrum modes equally, and DWCal fits calibration solutions preferentially from error-free modes. We apply this technique to simulated data, showing that it substantially reduces calibration error in the presence of realistic levels of sky model error and can improve 21 cm power spectrum sensitivity by approximately 2 orders of magnitude.

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Section: Introductionmentioning

confidence: 99%

Delay-weighted Calibration: Precision Calibration for 21 cm Cosmology with Resilience to Sky Model Error

Byrne

2023

ApJ

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A Bayesian approach to high-fidelity interferometric calibration – I. Mathematical formalism

Sims

Pober

Sievers

2022

Monthly Notices of the Royal Astronomical Society

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High-fidelity radio interferometric data calibration that minimizes spurious spectral structure in the calibrated data is essential in astrophysical applications, such as 21 cm cosmology, which rely on knowledge of the relative spectral smoothness of distinct astrophysical emission components to extract the signal of interest. Existing approaches to radio interferometric calibration have been shown to impart spurious spectral structure to the calibrated data if the sky model used to calibrate the data is incomplete. In this paper, we introduce BayesCal: a novel solution to the sky-model incompleteness problem in interferometric calibration, designed to enable high-fidelity data calibration. The BayesCal data model supplements the a priori known component of the forward model of the sky with a statistical model for the missing and uncertain flux contribution to the data, constrained by a prior on the power in the model. We demonstrate how the parameters of this model can be marginalized out analytically, reducing the dimensionality of the parameter space to be sampled from and allowing one to sample directly from the posterior probability distribution of the calibration parameters. Additionally, we show how physically motivated priors derived from theoretical and measurement-based constraints on the spectral smoothness of the instrumental gains can be used to constrain the calibration solutions. In a companion paper, we apply this algorithm to simulated observations with a HERA-like array and demonstrate that it enables up to four orders of magnitude suppression of power in spurious spectral fluctuations relative to standard calibration approaches.

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A general Bayesian framework to account for foreground map errors in global 21-cm experiments

Pagano,

Sims,

Liu

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Measurement of the global 21-cm signal during Cosmic Dawn and the Epoch of Reionization is made difficult by bright foreground emission which is 2–5 orders of magnitude larger than the expected signal. Fitting for a physics-motivated parametric forward model of the data within a Bayesian framework provides a robust means to separate the signal from the foregrounds, given sufficient information about the instrument and sky. It has previously been demonstrated that, within such a modelling framework, a foreground model of sufficient fidelity can be generated by dividing the sky into N regions and scaling a base map assuming a distinct uniform spectral index in each region. Using the Radio Experiment for the Analysis of Cosmic Hydrogen as our fiducial instrument, we show that, if unaccounted-for, amplitude errors in low-frequency radio maps used for our base map model will prevent recovery of the 21-cm signal within this framework, and that the level of bias in the recovered 21-cm signal is proportional to the amplitude and the correlation length of the base-map errors in the region. We introduce an updated foreground model that is capable of accounting for these measurement errors by fitting for a monopole offset and a set of spatially dependent scale factors describing the ratio of the true and model sky temperatures, with the size of the set determined by Bayesian evidence-based model comparison. We show that our model is flexible enough to account for multiple foreground error scenarios allowing the 21-cm sky-averaged signal to be detected without bias from simulated observations with a smooth conical log spiral antenna.

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A Bayesian approach to high fidelity interferometric calibration − II: demonstration with simulated data

Cited by 8 publications

References 77 publications

Delay-weighted Calibration: Precision Calibration for 21 cm Cosmology with Resilience to Sky Model Error

Delay-weighted Calibration: Precision Calibration for 21 cm Cosmology with Resilience to Sky Model Error

A Bayesian approach to high-fidelity interferometric calibration – I. Mathematical formalism

A general Bayesian framework to account for foreground map errors in global 21-cm experiments

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