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14 results on '"Razavi-Ghods, N."'

1. Understanding the HERA Phase i receiver system with simulations and its impact on the detectability of the EoR delay power spectrum

Author

Fagnoni, N, De Lera Acedo, E, Deboer, DR, Abdurashidova, Z, Aguirre, JE, Alexander, P, Ali, ZS, Balfour, Y, Beardsley, AP, Bernardi, G, Billings, TS, Bowman, JD, Bradley, RF, Bull, P, Burba, J, Carilli, CL, Cheng, C, Dexter, M, Dillon, JS, Ewall-Wice, A, Fritz, R, Furlanetto, SR, Gale-Sides, K, Glendenning, B, Gorthi, D, Greig, B, Grobbelaar, J, Halday, Z, Hazelton, BJ, Hewitt, JN, Hickish, J, Jacobs, DC, Josaitis, A, Julius, A, Kern, NS, Kerrigan, J, Kim, H, Kittiwisit, P, Kohn, SA, Kolopanis, M, Lanman, A, Plante, PL, Lekalake, T, Liu, A, Macmahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Matsetela, E, Mena Parra, J, Mesinger, A, Molewa, M, Morales, MF, Mosiane, T, Neben, AR, Nikolic, B, Parsons, AR, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Robnett, J, Rosie, K, Sims, P, Smith, C, Syce, A, Thyagarajan, N, Williams, PKG, and Zheng, H

Subjects
instrumentation: interferometers, methods: numerical, techniques: interferometric, telescopes, dark ages, reionization, first stars, astro-ph.IM, dark ages, reionization, Astronomy & Astrophysics, Astronomical and Space Sciences
Abstract

The detection of the Epoch of Reionization (EoR) delay power spectrum using a 'foreground avoidance method' highly depends on the instrument chromaticity. The systematic effects induced by the radio telescope spread the foreground signal in the delay domain, which contaminates the EoR window theoretically observable. Applied to the Hydrogen Epoch of Reionization Array (HERA), this paper combines detailed electromagnetic and electrical simulations in order to model the chromatic effects of the instrument, and quantify its frequency and time responses. In particular, the effects of the analogue receiver, transmission cables, and mutual coupling are included. These simulations are able to accurately predict the intensity of the reflections occurring in the 150-m cable which links the antenna to the backend. They also show that electromagnetic waves can propagate from one dish to another one through large sections of the array due to mutual coupling. The simulated system time response is attenuated by a factor 104 after a characteristic delay which depends on the size of the array and on the antenna position. Ultimately, the system response is attenuated by a factor 105 after 1400 ns because of the reflections in the cable, which corresponds to characterizable ka-modes above 0.7 $h\,\,\rm {Mpc}^{-1}$ at 150 MHz. Thus, this new study shows that the detection of the EoR signal with HERA Phase I will be more challenging than expected. On the other hand, it improves our understanding of the telescope, which is essential to mitigate the instrument chromaticity.

Published
2021

2. Foreground modelling via Gaussian process regression: An application to HERA data

Author

Ghosh, A, Mertens, F, Bernardi, G, Santos, MG, Kern, NS, Carilli, CL, Grobler, TL, Koopmans, LVE, Jacobs, DC, Liu, A, Parsons, AR, Morales, MF, Aguirre, JE, Dillon, JS, Hazelton, BJ, Smirnov, OM, Gehlot, BK, Matika, S, Alexander, P, Ali, ZS, Beardsley, AP, Benefo, RK, Billings, TS, Bowman, JD, Bradley, RF, Cheng, C, Chichura, PM, Deboer, DR, Acedo, EDL, Ewall-Wice, A, Fadana, G, Fagnoni, N, Fortino, AF, Fritz, R, Furlanetto, SR, Gallardo, S, Glendenning, B, Gorthi, D, Greig, B, Grobbelaar, J, Hickish, J, Josaitis, A, Julius, A, Igarashi, AS, Kariseb, M, Kohn, SA, Kolopanis, M, Lekalake, T, Loots, A, MacMahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Mathison, N, Matsetela, E, Mesinger, A, Neben, AR, Nikolic, B, Nunhokee, CD, Patra, N, Pieterse, S, Razavi-Ghods, N, Ringuette, J, Robnett, J, Rosie, K, Sell, R, Smith, C, Syce, A, Tegmark, M, Thyagarajan, N, Williams, PKG, and Zheng, H

Subjects
instrumentation: interferometers, methods: statistical, dark ages, reionization, first stars, diffuse radiation, large-scale structure of Universe, cosmology: observations, astro-ph.CO, dark ages, reionization, first stars, Astronomy & Astrophysics, Astronomical and Space Sciences
Abstract

The key challenge in the observation of the redshifted 21-cm signal from cosmic reionization is its separation from the much brighter foreground emission. Such separation relies on the different spectral properties of the two components, although, in real life, the foreground intrinsic spectrum is often corrupted by the instrumental response, inducing systematic effects that can further jeopardize the measurement of the 21-cm signal. In this paper, we use Gaussian Process Regression to model both foreground emission and instrumental systematics in ∼2 h of data from the Hydrogen Epoch of Reionization Array. We find that a simple co-variance model with three components matches the data well, giving a residual power spectrum with white noise properties. These consist of an 'intrinsic' and instrumentally corrupted component with a coherence scale of 20 and 2.4 MHz, respectively (dominating the line-of-sight power spectrum over scales kâ ≤ 0.2 h cMpc-1) and a baseline-dependent periodic signal with a period of ∼1 MHz (dominating over kâ ∼0.4-0.8 h cMpc-1), which should be distinguishable from the 21-cm Epoch of Reionization signal whose typical coherence scale is ∼0.8 MHz.

Published
2020

3. Redundant-baseline calibration of the hydrogen epoch of reionization array

Author

Dillon, JS, Lee, M, Ali, ZS, Parsons, AR, Orosz, N, Nunhokee, CD, La Plante, P, Beardsley, AP, Kern, NS, Abdurashidova, Z, Aguirre, JE, Alexander, P, Balfour, Y, Bernardi, G, Billings, TS, Bowman, JD, Bradley, RF, Bull, P, Burba, J, Carey, S, Carilli, CL, Cheng, C, DeBoer, DR, Dexter, M, de Lera Acedo, E, Ely, J, Ewall-Wice, A, Fagnoni, N, Fritz, R, Furlanetto, SR, Gale-Sides, K, Glendenning, B, Gorthi, D, Greig, B, Grobbelaar, J, Halday, Z, Hazelton, BJ, Hewitt, JN, Hickish, J, Jacobs, DC, Julius, A, Kerrigan, J, Kittiwisit, P, Kohn, SA, Kolopanis, M, Lanman, A, Lekalake, T, Lewis, D, Liu, A, Ma, YZ, MacMahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Matsetela, E, Mesinger, A, Molewa, M, Morales, MF, Mosiane, T, Murray, S, Neben, AR, Nikolic, B, Pascua, R, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Ringuette, J, Robnett, J, Rosie, K, Santos, MG, Sims, P, Smith, C, Syce, A, Tegmark, M, Thyagarajan, N, Williams, PKG, and Zheng, H

Subjects
instrumentation: interferometers, dark ages, reionization, first stars, astro-ph.IM, astro-ph.CO, dark ages, reionization, first stars, Astronomy & Astrophysics, Astronomical and Space Sciences
Abstract

In 21-cm cosmology, precision calibration is key to the separation of the neutral hydrogen signal from very bright but spectrally smooth astrophysical foregrounds. The Hydrogen Epoch of Reionization Array (HERA), an interferometer specialized for 21-cm cosmology and now under construction in South Africa, was designed to be largely calibrated using the self-consistency of repeated measurements of the same interferometric modes. This technique, known as redundant-baseline calibration resolves most of the internal degrees of freedom in the calibration problem. It assumes, however, on antenna elements with identical primary beams placed precisely on a redundant grid. In this work, we review the detailed implementation of the algorithms enabling redundant-baseline calibration and report results with HERA data.We quantify the effects of real-world non-redundancy and how they compare to the idealized scenario in which redundant measurements differ only in their noise realizations. Finally, we study how non-redundancy can produce spurious temporal structure in our calibration solutions-both in data and in simulations-and present strategies for mitigating that structure.

Published
2020

4. Optimizing sparse RFI prediction using deep learning

Author

Kerrigan, J, la Plante, P, Kohn, S, Pober, JC, Aguirre, J, Abdurashidova, Z, Alexander, P, Ali, ZS, Balfour, Y, Beardsley, AP, Bernardi, G, Bowman, JD, Bradley, RF, Burba, J, Carilli, CL, Cheng, C, DeBoer, DR, Dexter, M, de Lera Acedo, E, Dillon, JS, Estrada, J, Ewall-Wice, A, Fagnoni, N, Fritz, R, Furlanetto, SR, Glendenning, B, Greig, B, Grobbelaar, J, Gorthi, D, Halday, Z, Hazelton, BJ, Hickish, J, Jacobs, DC, Julius, A, Kern, NS, Kittiwisit, P, Kolopanis, M, Lanman, A, Lekalake, T, Liu, A, MacMahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Matsetela, E, Mesinger, A, Molewa, M, Morales, MF, Mosiane, T, Neben, AR, Parsons, AR, Patra, N, Pieterse, S, Razavi-Ghods, N, Ringuette, J, Robnett, J, Rosie, K, Sims, P, Smith, C, Syce, A, Thyagarajan, N, Williams, PKG, and Zheng, H

Subjects
methods: data analysis, techniques: interferometric, astro-ph.IM, astro-ph.CO, Astronomy & Astrophysics, Astronomical and Space Sciences
Abstract

Radio frequency interference (RFI) is an ever-present limiting factor among radio telescopes even in the most remote observing locations. When looking to retain the maximum amount of sensitivity and reduce contamination for Epoch of Reionization studies, the identification and removal of RFI is especially important. In addition to improved RFI identification, we must also take into account computational efficiency of the RFI-Identification algorithm as radio interferometer arrays such as the Hydrogen Epoch of Reionization Array (HERA) grow larger in number of receivers. To address this, we present a deep fully convolutional neural network (DFCN) that is comprehensive in its use of interferometric data, where both amplitude and phase information are used jointly for identifying RFI. We train the network using simulated HERA visibilities containing mock RFI, yielding a known ‘ground truth’ data set for evaluating the accuracy of various RFI algorithms. Evaluation of the DFCN model is performed on observations from the 67 dish build-out, HERA-67, and achieves a data throughput of 1.6 × 105 HERA time-ordered 1024 channelled visibilities per hour per GPU. We determine that relative to an amplitude only network including visibility phase adds important adjacent time–frequency context which increases discrimination between RFI and non-RFI. The inclusion of phase when predicting achieves a recall of 0.81, precision of 0.58, and F2 score of 0.75 as applied to our HERA-67 observations.

Published
2019

5. The HERA-19 Commissioning Array: Direction-dependent Effects

Author

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, and Zheng, H

Subjects
cosmology: observations, dark ages, reionization, first stars, instrumentation: interferometers, polarization, techniques: interferometric, astro-ph.IM, dark ages, reionization, first stars, Astronomy & Astrophysics, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural)
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.

Published
2019

6. The hydrogen epoch of reionization array dish III: measuring chromaticity of prototype element with reflectometry

Author

Patra, N, Parsons, AR, DeBoer, DR, Thyagarajan, N, Ewall-Wice, A, Hsyu, G, Leung, TK, Day, CK, de Lera Acedo, E, Aguirre, JE, Alexander, P, Ali, ZS, Beardsley, AP, Bowman, JD, Bradley, RF, Carilli, CL, Cheng, C, Dillon, JS, Fadana, G, Fagnoni, N, Fritz, R, Furlanetto, SR, Glendenning, B, Greig, B, Grobbelaar, J, Hazelton, BJ, Jacobs, DC, Julius, A, Kariseb, MC, Kohn, SA, Lebedeva, A, Lekalake, T, Liu, A, Loots, A, MacMahon, D, Malan, L, Malgas, C, Maree, M, Martinot, Z, Mathison, N, Matsetela, E, Mesinger, A, Morales, MF, Neben, AR, Pieterse, S, Pober, JC, Razavi-Ghods, N, Ringuette, J, Robnett, J, Rosie, K, Sell, R, Smith, C, Syce, A, Tegmark, M, Williams, PKG, and Zheng, H

Subjects
Astronomical instrumentation, Methods and techniques-wideband radio interferometry, Delay spectrum technique-EoR power spectrum, cm cosmology, astro-ph.IM, Astronomy & Astrophysics, Astronomical and Space Sciences
Abstract

Spectral structures due to the instrument response is the current limiting factor for the experiments attempting to detect the redshifted 21 cm signal from the Epoch of Reionization (EoR). Recent advances in the delay spectrum methodology for measuring the redshifted 21 cm EoR power spectrum brought new attention to the impact of an antenna’s frequency response on the viability of making this challenging measurement. The delay spectrum methodology provides a somewhat straightforward relationship between the time-domain response of an instrument that can be directly measured and the power spectrum modes accessible to a 21 cm EoR experiment. In this paper, we derive the explicit relationship between antenna reflection coefficient (S11) measurements made by a Vector Network Analyzer (VNA) and the extent of additional foreground contaminations in delay space. In the light of this mathematical framework, we examine the chromaticity of a prototype antenna element that will constitute the Hydrogen Epoch of Reionization Array (HERA) between 100 and 200 MHz. These reflectometry measurements exhibit additional structures relative to electromagnetic simulations, but we find that even without any further design improvement, such an antenna element will support measuring spatial k modes with line-of-sight components of k∥ > 0.2h Mpc− 1. We also find that when combined with the powerful inverse covariance weighting method used in optimal quadratic estimation of redshifted 21 cm power spectra the HERA prototype elements can successfully measure the power spectrum at spatial modes as low as k∥ > 0.1h Mpc− 1. This work represents a major step toward understanding the HERA antenna element and highlights a straightforward method for characterizing instrument response for future experiments designed to detect the 21 cm EoR power spectrum.

Published
2018

7. PAPER-64 CONSTRAINTS on REIONIZATION. II. the TEMPERATURE of the z = 8.4 INTERGALACTIC MEDIUM

Author

Pober, JC, Ali, ZS, Parsons, AR, McQuinn, M, Aguirre, JE, Bernardi, G, Bradley, RF, Carilli, CL, Cheng, C, Deboer, DR, Dexter, MR, Furlanetto, SR, Grobbelaar, J, Horrell, J, Jacobs, DC, Klima, PJ, Kohn, SA, Liu, A, Macmahon, DHE, Maree, M, Mesinger, A, Moore, DF, Razavi-Ghods, N, Stefan, II, Walbrugh, WP, Walker, A, and Zheng, H

Subjects
dark ages, reionization, first stars, galaxies: high-redshift, intergalactic medium, astro-ph.CO, dark ages, reionization, first stars, Astronomy & Astrophysics, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural)
Abstract

We present constraints on both the kinetic temperature of the intergalactic medium (IGM) at z = 8.4, and on models for heating the IGM at high-redshift with X-ray emission from the first collapsed objects. These constraints are derived using a semi-analytic method to explore the new measurements of the 21 cm power spectrum from the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER), which were presented in a companion paper, Ali et al. Twenty-one cm power spectra with amplitudes of hundreds of mK2 can be generically produced if the kinetic temperature of the IGM is significantly below the temperature of the cosmic microwave background (CMB); as such, the new results from PAPER place lower limits on the IGM temperature at z = 8.4. Allowing for the unknown ionization state of the IGM, our measurements find the IGM temperature to be above ≈5 K for neutral fractions between 10% and 85%, above ≈7 K for neutral fractions between 15% and 80%, or above ≈10 K for neutral fractions between 30% and 70%. We also calculate the heating of the IGM that would be provided by the observed high redshift galaxy population, and find that for most models, these galaxies are sufficient to bring the IGM temperature above our lower limits. However, there are significant ranges of parameter space that could produce a signal ruled out by the PAPER measurements; models with a steep drop-off in the star formation rate density at high redshifts or with relatively low values for the X-ray to star formation rate efficiency of high redshift galaxies are generally disfavored. The PAPER measurements are consistent with (but do not constrain) a hydrogen spin temperature above the CMB temperature, a situation which we find to be generally predicted if galaxies fainter than the current detection limits of optical/NIR surveys are included in calculations of X-ray heating.

Published
2015

8. Understanding the HERA Phase i receiver system with simulations and its impact on the detectability of the EoR delay power spectrum

Author

Fagnoni, N, De Lera Acedo, E, Deboer, DR, Abdurashidova, Z, Aguirre, JE, Alexander, P, Ali, ZS, Balfour, Y, Beardsley, AP, Bernardi, G, Billings, TS, Bowman, JD, Bradley, RF, Bull, P, Burba, J, Carilli, CL, Cheng, C, Dexter, M, Dillon, JS, Ewall-Wice, A, Fritz, R, Furlanetto, SR, Gale-Sides, K, Glendenning, B, Gorthi, D, Greig, B, Grobbelaar, J, Halday, Z, Hazelton, BJ, Hewitt, JN, Hickish, J, Jacobs, DC, Josaitis, A, Julius, A, Kern, NS, Kerrigan, J, Kim, H, Kittiwisit, P, Kohn, SA, Kolopanis, M, Lanman, A, Plante, PL, Lekalake, T, Liu, A, Macmahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Matsetela, E, Mena Parra, J, Mesinger, A, Molewa, M, Morales, MF, Mosiane, T, Neben, AR, Nikolic, B, Parsons, AR, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Robnett, J, Rosie, K, Sims, P, Smith, C, Syce, A, Thyagarajan, N, Williams, PKG, Zheng, H, De Lera Acedo, Eloy [0000-0001-8530-6989], Alexander, Paul [0000-0002-0292-9513], Nikolic, Bojan [0000-0001-7168-2705], Razavi-Ghods, Nima [0000-0003-2930-5396], and Apollo - University of Cambridge Repository

Subjects
interferometers [instrumentation], first stars, Astrophysics::Instrumentation and Methods for Astrophysics, numerical [methods], telescopes, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, interferometric [techniques], methods: numerical, dark ages, reionization, techniques: interferometric, reionization, dark ages, instrumentation: interferometers, Astronomical and Space Sciences, astro-ph.IM
Abstract

The detection of the Epoch of Reionization (EoR) delay power spectrum using a "foreground avoidance method" highly depends on the instrument chromaticity. The systematic effects induced by the radio-telescope spread the foreground signal in the delay domain, which contaminates the EoR window theoretically observable. Applied to the Hydrogen Epoch of Reionization Array (HERA), this paper combines detailed electromagnetic and electrical simulations in order to model the chromatic effects of the instrument, and quantify its frequency and time responses. In particular, the effects of the analogue receiver, transmission cables, and mutual coupling are included. These simulations are able to accurately predict the intensity of the reflections occurring in the 150-m cable which links the antenna to the back-end. They also show that electromagnetic waves can propagate from one dish to another one through large sections of the array due to mutual coupling. The simulated system time response is attenuated by a factor $10^{4}$ after a characteristic delay which depends on the size of the array and on the antenna position. Ultimately, the system response is attenuated by a factor $10^{5}$ after 1400 ns because of the reflections in the cable, which corresponds to characterizable ${k_\parallel}$-modes above 0.7 $h\;\rm{Mpc}^{-1}$ at 150 MHz. Thus, this new study shows that the detection of the EoR signal with HERA Phase I will be more challenging than expected. On the other hand, it improves our understanding of the telescope, which is essential to mitigate the instrument chromaticity.

Published
2020
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9. Foreground modelling via Gaussian process regression: an application to HERA data

Author

Max Tegmark, Aaron R. Parsons, Samavarti Gallardo, Angelo Syce, Jon Ringuette, Adam P. Beardsley, Gianni Bernardi, Richard F. Bradley, Matthew Kolopanis, Mario G. Santos, Adrian Liu, Kathryn Rosie, T. L. Grobler, Nicholas S. Kern, Brian Glendenning, Amy S. Igarashi, Siyanda Matika, Daniel C. Jacobs, Carina Cheng, Oleg Smirnov, Nithyanandan Thyagarajan, Haoxuan Zheng, Peter K. G. Williams, Matthys Maree, Roshan K. Benefo, Nathan Mathison, Lourence Malan, Austin Julius, Nima Razavi-Ghods, Cresshim Malgas, B. K. Gehlot, Nicolas Fagnoni, Bryna J. Hazelton, Andrei Mesinger, Chuneeta D. Nunhokee, Jasper Grobbelaar, David MacMahon, Deepthi Gorthi, Léon V. E. Koopmans, Joshua S. Dillon, Steve R. Furlanetto, Abraham R. Neben, Chris Carilli, Tashalee S. Billings, Zachary E. Martinot, Judd D. Bowman, Samantha Pieterse, Paul Alexander, Randall Fritz, James Robnett, Telalo Lekalake, Raddwine Sell, Saul A. Kohn, Eloy de Lera Acedo, Florent Mertens, Alec Josaitis, Bradley Greig, Nipanjana Patra, Craig Smith, Austin F. Fortino, David DeBoer, Miguel F. Morales, Zaki S. Ali, Bojan Nikolic, Aaron Ewall-Wice, Eunice Matsetela, MacCalvin Kariseb, Gcobisa Fadana, Paul M. Chichura, Jack Hickish, James E. Aguirre, Abhik Ghosh, Anita Loots, Ghosh, A., Mertens, F., Bernardi, G., Santos, M. G., Kern, N. S., Carilli, C. L., Grobler, T. L., Koopmans, L. V. E., Jacobs, D. C., Liu, A., Parsons, A. R., Morales, M. F., Aguirre, J. E., Dillon, J. S., Hazelton, B. J., Smirnov, O. M., Gehlot, B. K., Matika, S., Alexander, P., Ali, Z. S., Beardsley, A. P., Benefo, R. K., Billings, T. S., Bowman, J. D., Bradley, R. F., Cheng, C., Chichura, P. M., Deboer, D. R., Acedo, E. D. L., Ewall-Wice, A., Fadana, G., Fagnoni, N., Fortino, A. F., Fritz, R., Furlanetto, S. R., Gallardo, S., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Hickish, J., Josaitis, A., Julius, A., Igarashi, A. S., Kariseb, M., Kohn, S. A., Kolopanis, M., Lekalake, T., Loots, A., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Mathison, N., Matsetela, E., Mesinger, A., Neben, A. R., Nikolic, B., Nunhokee, C. D., Patra, N., Pieterse, S., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Sell, R., Smith, C., Syce, A., Tegmark, M., Thyagarajan, N., Williams, P. K. G., Zheng, H., Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), ITA, USA, ZAF, Astronomy, and Kapteyn Astronomical Institute

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), interferometers [instrumentation], first stars, statistical [methods], FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astronomy & Astrophysics, 01 natural sciences, Signal, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, Coherence (signal processing), dark ages, reionization, first stars, dark ages, instrumentation: interferometers, 010306 general physics, 010303 astronomy & astrophysics, Reionization, Astrophysics::Galaxy Astrophysics, Physics, methods: statistical, COSMIC cancer database, Astrophysics::Instrumentation and Methods for Astrophysics, Spectral density, Astronomy and Astrophysics, White noise, observations [cosmology], Redshift, diffuse radiation, Periodic function, interferometer [instrumentation], Space and Planetary Science, cosmology: observations, astro-ph.CO, reionization, dark ages, reionization, first star, large-scale structure of Universe, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astronomical and Space Sciences, Astrophysics - Cosmology and Nongalactic Astrophysics, observation [cosmology]
Abstract

The key challenge in the observation of the redshifted 21-cm signal from cosmic reionization is its separation from the much brighter foreground emission. Such separation relies on the different spectral properties of the two components, although, in real life, the foreground intrinsic spectrum is often corrupted by the instrumental response, inducing systematic effects that can further jeopardize the measurement of the 21-cm signal. In this paper, we use Gaussian Process Regression to model both foreground emission and instrumental systematics in $\sim 2$ hours of data from the Hydrogen Epoch of Reionization Array. We find that a simple co-variance model with three components matches the data well, giving a residual power spectrum with white noise properties. These consist of an "intrinsic" and instrumentally corrupted component with a coherence-scale of 20 MHz and 2.4 MHz respectively (dominating the line of sight power spectrum over scales $k_{\parallel} \le 0.2$ h cMpc$^{-1}$) and a baseline dependent periodic signal with a period of $\sim 1$ MHz (dominating over $k_{\parallel} \sim 0.4 - 0.8$h cMpc$^{-1}$) which should be distinguishable from the 21-cm EoR signal whose typical coherence-scales is $\sim 0.8$ MHz., 15 pages, 15 figures, 1 table, Accepted to MNRAS

Published
2020

10. Redundant-baseline calibration of the hydrogen epoch of reionization array

Author

Adrian Liu, Craig Smith, Paul Alexander, John Ely, Deepthi Gorthi, Nithyanandan Thyagarajan, Steven G. Murray, Joshua S. Dillon, Bryna J. Hazelton, Phil Bull, Nipanjana Patra, Jon Ringuette, Zara Abdurashidova, Ziyaad Halday, Aaron R. Parsons, Bradley Greig, Lourence Malan, Angelo Syce, Gianni Bernardi, Piyanat Kittiwisit, Austin Julius, Daniel C. Jacobs, Kingsley Gale-Sides, Jack Hickish, Yin-Zhe Ma, Jonathan C. Pober, Kathryn Rosie, Adam P. Beardsley, Robert Pascua, Peter K. G. Williams, Cresshim Malgas, S. H. Carey, Jacob Burba, Nicolas Fagnoni, David MacMahon, Andrei Mesinger, Jasper Grobbelaar, Yanga Balfour, Joshua Kerrigan, Max Tegmark, Richard F. Bradley, Matthew Kolopanis, David DeBoer, Abraham R. Neben, Mario G. Santos, Randall Fritz, Jacqueline N. Hewitt, Tashalee S. Billings, Zachary E. Martinot, Eunice Matsetela, Saul A. Kohn, David Lewis, Peter Sims, Mathakane Molewa, Naomi Orosz, Steven R. Furlanetto, Paul La Plante, Chuneeta D. Nunhokee, Matt Dexter, Tshegofalang Mosiane, Nicholas S. Kern, Judd D. Bowman, Samantha Pieterse, Max E. Lee, James E. Aguirre, Nima Razavi-Ghods, Miguel F. Morales, Zaki S. Ali, Bojan Nikolic, Aaron Ewall-Wice, Chris Carilli, Eloy de Lera Acedo, James Robnett, Brian Glendenning, Carina Cheng, Matthys Maree, Telalo Lekalake, Haoxuan Zheng, Adam Lanman, ITA, USA, ZAF, Dillon, J. S., Lee, M., Ali, Z. S., Parsons, A. R., Orosz, N., Nunhokee, C. D., La Plante, P., Beardsley, A. P., Kern, N. S., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Balfour, Y., Bernardi, G., Billings, T. S., Bowman, J. D., Bradley, R. F., Bull, P., Burba, J., Carey, S., Carilli, C. L., Cheng, C., Deboer, D. R., Dexter, M., de Lera Acedo, E., Ely, J., Ewall-Wice, A., Fagnoni, N., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Hewitt, J. N., Hickish, J., Jacobs, D. C., Julius, A., Kerrigan, J., Kittiwisit, P., Kohn, S. A., Kolopanis, M., Lanman, A., Lekalake, T., Lewis, D., Liu, A., Ma, Y. -Z., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mesinger, A., Molewa, M., Morales, M. F., Mosiane, T., Murray, S., Neben, A. R., Nikolic, B., Pascua, R., Patra, N., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Santos, M. G., Sims, P., Smith, C., Syce, A., Tegmark, M., Thyagarajan, N., Williams, P. K. G., Zheng, H., Alexander, Paul [0000-0002-0292-9513], De Lera Acedo, Eloy [0000-0001-8530-6989], Nikolic, Bojan [0000-0001-7168-2705], Razavi-Ghods, Nima [0000-0003-2930-5396], and Apollo - University of Cambridge Repository

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), Calibration (statistics), interferometers [instrumentation], first stars, Degrees of freedom (statistics), FOS: Physical sciences, Astronomy & Astrophysics, 01 natural sciences, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, Astronomical interferometer, dark ages, reionization, first stars, dark ages, instrumentation: interferometers, 010303 astronomy & astrophysics, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), Physics, 010308 nuclear & particles physics, Noise (signal processing), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, HERA, Interferometry, Dark ages, reionization, first star, Space and Planetary Science, astro-ph.CO, reionization, Antenna (radio), Astrophysics - Instrumentation and Methods for Astrophysics, Algorithm, Astronomical and Space Sciences, Astrophysics - Cosmology and Nongalactic Astrophysics, astro-ph.IM
Abstract

In 21 cm cosmology, precision calibration is key to the separation of the neutral hydrogen signal from very bright but spectrally-smooth astrophysical foregrounds. The Hydrogen Epoch of Reionization Array (HERA), an interferometer specialized for 21 cm cosmology and now under construction in South Africa, was designed to be largely calibrated using the self-consistency of repeated measurements of the same interferometric modes. This technique, known as "redundant-baseline calibration" resolves most of the internal degrees of freedom in the calibration problem. It assumes, however, on antenna elements with identical primary beams placed precisely on a redundant grid. In this work, we review the detailed implementation of the algorithms enabling redundant-baseline calibration and report results with HERA data. We quantify the effects of real-world non-redundancy and how they compare to the idealized scenario in which redundant measurements differ only in their noise realizations. Finally, we study how non-redundancy can produce spurious temporal structure in our calibration solutions--both in data and in simulations--and present strategies for mitigating that structure., Comment: 24 Pages, 19 Figures. Updated to match the accepted MNRAS version

Published
2020

11. Detection of cosmic structures using the bispectrum phase. II. First results from application to cosmic reionization using the Hydrogen Epoch of Reionization Array

Author

Kathryn Rosie, James E. Aguirre, Jonathan C. Pober, Andrei Mesinger, Jasper Grobbelaar, David MacMahon, Nipanjana Patra, Tashalee S. Billings, Zachary E. Martinot, Ziyaad Halday, Deepthi Gorthi, Joshua S. Dillon, S. H. Carey, Paul Alexander, Haoxuan Zheng, Eunice Matsetela, Piyanat Kittiwisit, Adam P. Beardsley, Saul A. Kohn, Jon Ringuette, Kingsley Gale-Sides, Joshua Kerrigan, John Ely, Siyanda Matika, Zara Abdurashidova, David DeBoer, Nithyanandan Thyagarajan, Aaron R. Parsons, Matt Dexter, Bryna J. Hazelton, Adrian Liu, Nicholas S. Kern, James Kent, Jack Hickish, Judd D. Bowman, Samantha Pieterse, James Robnett, Miguel F. Morales, Paul La Plante, Richard F. Bradley, Matthew Kolopanis, Austin Julius, Chris Carilli, Eloy de Lera Acedo, Peter K. G. Williams, Craig Smith, Jacob Burba, Zaki S. Ali, Brian Glendenning, Jacqueline N. Hewitt, Carina Cheng, Gianni Bernardi, David B. Lewis, Bojan Nikolic, Aaron Ewall-Wice, Abraham R. Neben, Randall Fritz, Steven R. Furlanetto, Mathakane Molewa, Tshegofalang Mosiane, Lourence Malan, Bradley Greig, Nima Razavi-Ghods, Adam Lanman, Peter Sims, Daniel C. Jacobs, Cresshim Malgas, Nicolas Fagnoni, Yanga Balfour, Angelo Syce, Telalo Lekalake, Matthys Maree, Thyagarajan, N., Carilli, C. L., Nikolic, B., Kent, J., Mesinger, A., Kern, N. S., Bernardi, G., Matika, S., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Ali, Z. S., Balfour, Y., Beardsley, A. P., Billings, T. S., Bowman, J. D., Bradley, R. F., Burba, J., Carey, S., Cheng, C., Deboer, D. R., Dexter, M., Acedo, E. D. L., Dillon, J. S., Ely, J., Ewall-Wice, A., Fagnoni, N., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Hewitt, J. N., Hickish, J., Jacobs, D. C., Julius, A., Kerrigan, J., Kittiwisit, P., Kohn, S. A., Kolopanis, M., Lanman, A., La Plante, P., Lekalake, T., Lewis, D., Liu, A., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Molewa, M., Morales, M. F., Mosiane, T., Neben, A. R., Parsons, A. R., Patra, N., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Sims, P., Smith, C., Syce, A., Williams, P. K. G., Zheng, H., Nikolic, Bojan [0000-0001-7168-2705], Kent, James [0000-0003-3331-2409], Alexander, Paul [0000-0002-0292-9513], Razavi-Ghods, Nima [0000-0003-2930-5396], Apollo - University of Cambridge Repository, ITA, USA, and ZAF

Subjects
Brightness, Cosmology and Nongalactic Astrophysics (astro-ph.CO), FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Atomic, 01 natural sciences, Cosmology, Radio telescope, Particle and Plasma Physics, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, Nuclear, Astrophysics - Cosmology and Nongalactic Astrophysic, 010306 general physics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Reionization, Physics, Quantum Physics, COSMIC cancer database, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Molecular, Nuclear & Particles Physics, Redshift, 5101 Astronomical Sciences, astro-ph.CO, Hydrogen line, Astrophysics - Instrumentation and Methods for Astrophysics, 51 Physical Sciences, Bispectrum, Astronomical and Space Sciences, astro-ph.IM, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Characterizing the epoch of reionization (EoR) at $z\gtrsim 6$ via the redshifted 21 cm line of neutral Hydrogen (HI) is critical to modern astrophysics and cosmology, and thus a key science goal of many current and planned low-frequency radio telescopes. The primary challenge to detecting this signal is the overwhelmingly bright foreground emission at these frequencies, placing stringent requirements on the knowledge of the instruments and inaccuracies in analyses. Results from these experiments have largely been limited not by thermal sensitivity but by systematics, particularly caused by the inability to calibrate the instrument to high accuracy. The interferometric bispectrum phase is immune to antenna-based calibration and errors therein, and presents an independent alternative to detect the EoR HI fluctuations while largely avoiding calibration systematics. Here, we provide a demonstration of this technique on a subset of data from the Hydrogen Epoch of Reionization Array (HERA) to place approximate constraints on the brightness temperature of the intergalactic medium (IGM). From this limited data, at $z=7.7$ we infer "$1\sigma$" upper limits on the IGM brightness temperature to be $\le 316$ "pseudo" mK at $\kappa_\parallel=0.33$ "pseudo" $h$ Mpc$^{-1}$ (data-limited) and $\le 1000$ "pseudo" mK at $\kappa_\parallel=0.875$ "pseudo" $h$ Mpc$^{-1}$ (noise-limited). The "pseudo" units denote only an approximate and not an exact correspondence to the actual distance scales and brightness temperatures. By propagating models in parallel to the data analysis, we confirm that the dynamic range required to separate the cosmic HI signal from the foregrounds is similar to that in standard approaches, and the power spectrum of the bispectrum phase is still data-limited (at $\gtrsim 10^6$ dynamic range) indicating scope for further improvement in sensitivity as the array build-out continues., Comment: 22 pages, 12 figures (including sub-figures). Published in PhRvD. Abstract may be slightly abridged compared to the actual manuscript due to length limitations on arXiv

Published
2020

12. Optimizing sparse RFI prediction using deep learning

Author

Nithyanandan Thyagarajan, Adam Lanman, Kathryn Rosie, Angelo Syce, Gianni Bernardi, Deepthi Gorthi, Joshua S. Dillon, Peter Sims, Judd D. Bowman, Brian Glendenning, Carina Cheng, Samantha Pieterse, Craig Smith, Nicholas S. Kern, Eunice Matsetela, Joshua Kerrigan, Miguel F. Morales, Piyanat Kittiwisit, Mathakane Molewa, Zaki S. Ali, Paul Alexander, Tshegofalang Mosiane, Aaron Ewall-Wice, Daniel C. Jacobs, Jack Hickish, Haoxuan Zheng, David MacMahon, Telalo Lekalake, Matt Dexter, Cresshim Malgas, Nicolas Fagnoni, Jacob Burba, Yanga Balfour, Adam P. Beardsley, Bradley Greig, Abraham R. Neben, Steve R. Furlanetto, Matthys Maree, Julia Estrada, David DeBoer, Randall Fritz, James E. Aguirre, Nipanjana Patra, Peter K. G. Williams, Nima Razavi-Ghods, Ziyaad Halday, Richard F. Bradley, Matthew Kolopanis, Paul La Plante, Aaron R. Parsons, Lourence Malan, Adrian Liu, Zara Abdurashidova, Austin Julius, Eloy de Lera Acedo, Jon Ringuette, James Robnett, Jonathan C. Pober, Andrei Mesinger, Jasper Grobbelaar, Saul A. Kohn, Chris Carilli, Zachary E. Martinot, Bryna J. Hazelton, USA, Kerrigan, J., la Plante, P., Kohn, S., Pober, J. C., Aguirre, J., Abdurashidova, Z., Alexander, P., Ali, Z. S., Balfour, Y., Beardsley, A. P., Bernardi, G., Bowman, J. D., Bradley, R. F., Burba, J., Carilli, C. L., Cheng, C., Deboer, D. R., Dexter, M., de Lera Acedo, E., Dillon, J. S., Estrada, J., Ewall-Wice, A., Fagnoni, N., Fritz, R., Furlanetto, S. R., Glendenning, B., Greig, B., Grobbelaar, J., Gorthi, D., Halday, Z., Hazelton, B. J., Hickish, J., Jacobs, D. C., Julius, A., Kern, N. S., Kittiwisit, P., Kolopanis, M., Lanman, A., Lekalake, T., Liu, A., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mesinger, A., Molewa, M., Morales, M. F., Mosiane, T., Neben, A. R., Parsons, A. R., Patra, N., Pieterse, S., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Sims, P., Smith, C., Syce, A., Thyagarajan, N., Williams, P. K. G., and Zheng, H.

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), FOS: Physical sciences, Context (language use), 02 engineering and technology, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, 01 natural sciences, Radio telescope, Settore FIS/05 - Astronomia e Astrofisica, 020204 information systems, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, data analysis [methods], 010303 astronomy & astrophysics, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), Discrete mathematics, Physics, business.industry, Deep learning, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, HERA, interferometric [techniques], Amplitude, Space and Planetary Science, data analysis – Techniques: interferometric [Methods], astro-ph.CO, Artificial intelligence, Radio interferometer, Astrophysics - Instrumentation and Methods for Astrophysics, business, Astronomical and Space Sciences, Astrophysics - Cosmology and Nongalactic Astrophysics, astro-ph.IM
Abstract

Radio Frequency Interference (RFI) is an ever-present limiting factor among radio telescopes even in the most remote observing locations. When looking to retain the maximum amount of sensitivity and reduce contamination for Epoch of Reionization studies, the identification and removal of RFI is especially important. In addition to improved RFI identification, we must also take into account computational efficiency of the RFI-Identification algorithm as radio interferometer arrays such as the Hydrogen Epoch of Reionization Array grow larger in number of receivers. To address this, we present a Deep Fully Convolutional Neural Network (DFCN) that is comprehensive in its use of interferometric data, where both amplitude and phase information are used jointly for identifying RFI. We train the network using simulated HERA visibilities containing mock RFI, yielding a known "ground truth" dataset for evaluating the accuracy of various RFI algorithms. Evaluation of the DFCN model is performed on observations from the 67 dish build-out, HERA-67, and achieves a data throughput of 1.6$\times 10^{5}$ HERA time-ordered 1024 channeled visibilities per hour per GPU. We determine that relative to an amplitude only network including visibility phase adds important adjacent time-frequency context which increases discrimination between RFI and Non-RFI. The inclusion of phase when predicting achieves a Recall of 0.81, Precision of 0.58, and $F_{2}$ score of 0.75 as applied to our HERA-67 observations., Comment: 11 pages, 7 figures

Published
2019

13. Understanding the HERA Phase I receiver system with simulations and its impact on the detectability of the EoR delay power spectrum

Author

Richard F. Bradley, Matthew Kolopanis, Nithyanandan Thyagarajan, Adam Lanman, Lourence Malan, Saul A. Kohn, Alec Josaitis, Adrian Liu, Bryna J. Hazelton, Matt Dexter, Haoxuan Zheng, Piyanat Kittiwisit, Nicholas S. Kern, Kingsley Gale-Sides, Deepthi Gorthi, Joshua S. Dillon, Paul Alexander, Honggeun Kim, Craig Smith, Miguel F. Morales, Steve R. Furlanetto, Adam P. Beardsley, Mathakane Molewa, Zaki S. Ali, Bojan Nikolic, Aaron Ewall-Wice, Tshegofalang Mosiane, Phil Bull, Nipanjana Patra, Jacqueline N. Hewitt, Ziyaad Halday, Angelo Syce, Abraham R. Neben, Randall Fritz, Juan Mena Parra, Jack Hickish, Aaron R. Parsons, Joshua Kerrigan, Brian Glendenning, Carina Cheng, Paul La Plante, James Robnett, Jacob Burba, Chris Carilli, Eloy de Lera Acedo, Telalo Lekalake, Zara Abdurashidova, Kathryn Rosie, Gianni Bernardi, David MacMahon, Austin Julius, Daniel C. Jacobs, Nima Razavi-Ghods, Cresshim Malgas, Nicolas Fagnoni, Yanga Balfour, Matthys Maree, Peter Sims, Jonathan C. Pober, Andrei Mesinger, Jasper Grobbelaar, Tashalee S. Billings, Zachary E. Martinot, Bradley Greig, James E. Aguirre, Peter K. G. Williams, Eunice Matsetela, Judd D. Bowman, Samantha Pieterse, David DeBoer, ITA, USA, GBR, Fagnoni, N., De Lera Acedo, E., Deboer, D. R., Abdurashidova, Z., Aguirre, J. E., Alexander, P., Ali, Z. S., Balfour, Y., Beardsley, A. P., Bernardi, G., Billings, T. S., Bowman, J. D., Bradley, R. F., Bull, P., Burba, J., Carilli, C. L., Cheng, C., Dexter, M., Dillon, J. S., Ewall-Wice, A., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Hewitt, J. N., Hickish, J., Jacobs, D. C., Josaitis, A., Julius, A., Kern, N. S., Kerrigan, J., Kim, H., Kittiwisit, P., Kohn, S. A., Kolopanis, M., Lanman, A., Plante, P. L., Lekalake, T., Liu, A., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mena Parra, J., Mesinger, A., Molewa, M., Morales, M. F., Mosiane, T., Neben, A. R., Nikolic, B., Parsons, A. R., Patra, N., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Robnett, J., Rosie, K., Sims, P., Smith, C., Syce, A., Thyagarajan, N., Williams, P. K. G., and Zheng, H.

Subjects
interferometers [instrumentation], first stars, Phase (waves), FOS: Physical sciences, 02 engineering and technology, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, 01 natural sciences, law.invention, Radio telescope, Telescope, Optics, Settore FIS/05 - Astronomia e Astrofisica, law, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, dark ages, 010303 astronomy & astrophysics, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), Physics, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Spectral density, 020206 networking & telecommunications, Astronomy and Astrophysics, numerical [methods], telescopes, HERA, interferometric [techniques], interferometer [instrumentation], Transmission (telecommunications), Space and Planetary Science, reionization, dark ages, reionization, first star, Antenna (radio), Astrophysics - Instrumentation and Methods for Astrophysics, business, Astronomical and Space Sciences, astro-ph.IM
Abstract

The detection of the Epoch of Reionization (EoR) delay power spectrum using a "foreground avoidance method" highly depends on the instrument chromaticity. The systematic effects induced by the radio-telescope spread the foreground signal in the delay domain, which contaminates the EoR window theoretically observable. Applied to the Hydrogen Epoch of Reionization Array (HERA), this paper combines detailed electromagnetic and electrical simulations in order to model the chromatic effects of the instrument, and quantify its frequency and time responses. In particular, the effects of the analogue receiver, transmission cables, and mutual coupling are included. These simulations are able to accurately predict the intensity of the reflections occurring in the 150-m cable which links the antenna to the back-end. They also show that electromagnetic waves can propagate from one dish to another one through large sections of the array due to mutual coupling. The simulated system time response is attenuated by a factor $10^{4}$ after a characteristic delay which depends on the size of the array and on the antenna position. Ultimately, the system response is attenuated by a factor $10^{5}$ after 1400 ns because of the reflections in the cable, which corresponds to characterizable ${k_\parallel}$-modes above 0.7 $h\;\rm{Mpc}^{-1}$ at 150 MHz. Thus, this new study shows that the detection of the EoR signal with HERA Phase I will be more challenging than expected. On the other hand, it improves our understanding of the telescope, which is essential to mitigate the instrument chromaticity., Comment: 13 pages, 17 figures - Submitted to MNRAS - 2nd revision

Published
2019
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14. The HERA-19 Commissioning Array: Direction-dependent Effects

Author

Judd D. Bowman, Samantha Pieterse, Daniel C. Jacobs, Gcobisa Fadana, Paul M. Chichura, C. H. Smith, Jacqueline N. Hewitt, Richard F. Bradley, Matthew Kolopanis, Joshua S. Dillon, Jon Ringuette, Cresshim Malgas, Jonathan C. Pober, Andrei Mesinger, Nicolas Fagnoni, Jasper Grobbelaar, Chris Carilli, Nima Razavi-Ghods, Tashalee S. Billings, Zachary E. Martinot, Eloy de Lera Acedo, David DeBoer, Chuneeta D. Nunhokee, Miguel F. Morales, Roshan K. Benefo, Haoxuan Zheng, Brian Glendenning, Austin Julius, Amy S. Igarashi, Gianni Bernardi, Carina Cheng, Zaki S. Ali, Nipanjana Patra, Bojan Nikolic, Aaron Ewall-Wice, Anita Loots, Angelo Syce, Peter Williams, Paul Alexander, Lourence Malan, Eunice Matsetela, Nithyanandan Thyagarajan, Steven R. Furlanetto, James E. Aguirre, Raddwine Sell, MacCalvin Kariseb, Telalo Lekalake, Max Tegmark, Matthys Maree, Bryna J. Hazelton, Bradley Greig, Adrian Liu, Jack Hickish, Nicholas S. Kern, Paul La Plante, Abraham R. Neben, Randall Fritz, Aaron R. Parsons, Samavarti Gallardo, Austin F. Fortino, Philip Bull, James Robnett, David MacMahon, Adam P. Beardsley, Saul A. Kohn, Kathryn Rosie, Nathan Mathison, ITA, USA, Kohn, SA [0000-0001-6744-5328], Aguirre, JE [0000-0002-4810-666X], La Plante, P [0000-0002-4693-0102], Nunhokee, CD [0000-0002-5445-6586], Kern, NS [0000-0002-8211-1892], Liu, A [0000-0001-6876-0928], Beardsley, AP [0000-0001-9428-8233], Bernardi, G [0000-0002-0916-7443], Bowman, JD [0000-0002-8475-2036], Carilli, CL [0000-0001-6647-3861], Dillon, JS [0000-0003-3336-9958], Ewall-Wice, A [0000-0002-0086-7363], Furlanetto, SR [0000-0002-0658-1243], Hazelton, BJ [0000-0001-7532-645X], Jacobs, DC [0000-0002-0917-2269], Kolopanis, M [0000-0002-2950-2974], Morales, MF [0000-0001-7694-4030], Neben, AR [0000-0001-7776-7240], Patra, N [0000-0002-9457-1941], Tegmark, M [0000-0001-7670-7190], Thyagarajan, N [0000-0003-1602-7868], Williams, PKG [0000-0003-3734-3587], Apollo - University of Cambridge Repository, Kohn, S. A., Aguirre, J. E., La Plante, P., Billings, T. S., Chichura, P. M., Fortino, A. F., Igarashi, A. S., Benefo, R. K., Gallardo, S., Martinot, Z. E., Nunhokee, C. D., Kern, N. S., Bull, P., Liu, A., Alexander, P., Ali, Z. S., Beardsley, A. P., Bernardi, G., Bowman, J. D., Bradley, R. F., Carilli, C. L., Cheng, C., Deboer, D. R., Acedo, E. D. L., Dillon, J. S., Ewall-Wice, A., Fadana, G., Fagnoni, N., Furlanetto, S. R., Glendenning, B., Greig, B., Grobbelaar, J., Hazelton, B. J., Hewitt, J. N., Hickish, J., Jacobs, D. C., 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, M. F., Neben, A. R., Nikolic, B., Parsons, A. R., Patra, N., Pieterse, S., Pober, J. C., Randall, F., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Sell, R., Smith, C., Syce, A., Tegmark, M., Thyagarajan, N., Williams, P. K. G., and Zheng, H.

Subjects
010504 meteorology & atmospheric sciences, interferometers [instrumentation], Atomic, Physical Chemistry, 7. Clean energy, 01 natural sciences, Spectral line, Particle and Plasma Physics, Astronomical interferometer, Stokes parameters, dark ages, instrumentation: interferometers, 010303 astronomy & astrophysics, Physics, Linear polarization, Astrophysics::Instrumentation and Methods for Astrophysics, HERA, Polarization (waves), observations [cosmology], interferometric [techniques], interferometer [instrumentation], Amplitude, techniques: interferometric, symbols, reionization, dark ages, reionization, first star, Astrophysics - Instrumentation and Methods for Astrophysics, Astronomical and Space Sciences, observation [cosmology], Physical Chemistry (incl. Structural), first stars, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, symbols.namesake, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, Nuclear, dark ages, reionization, first stars, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, polarization, 010308 nuclear & particles physics, Molecular, Astronomy and Astrophysics, Computational physics, Space and Planetary Science, 13. Climate action, cosmology: observations, astro-ph.IM
Abstract

Foreground power dominates the measurements of interferometers that seek a statistical detection of highly-redshifted HI emission from the Epoch of Reionization (EoR). The chromaticity of the instrument creates a boundary in the Fourier transform of frequency (proportional to $k_\parallel$) between spectrally smooth emission, characteristic of the strong synchrotron foreground (the "wedge"), and the spectrally structured emission from HI 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. 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. 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 the expected level. Further, 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., Comment: 21 pages, 12 figures, submitted to ApJ

Published
2018
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