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

Author

Thyagarajan, N, Carilli, CL, Nikolic, B, Kent, J, Mesinger, A, Kern, NS, Bernardi, G, Matika, S, Abdurashidova, Z, Aguirre, JE, Alexander, P, Ali, ZS, Balfour, Y, Beardsley, AP, Billings, TS, Bowman, JD, Bradley, RF, Burba, J, Carey, S, Cheng, C, Deboer, DR, Dexter, M, Acedo, EDL, Dillon, JS, 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, La Plante, P, Lekalake, T, Lewis, D, Liu, A, Macmahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Matsetela, E, Molewa, M, Morales, MF, Mosiane, T, Neben, AR, Parsons, AR, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Ringuette, J, Robnett, J, Rosie, K, Sims, P, Smith, C, Syce, A, Williams, PKG, and Zheng, H

Subjects
astro-ph.CO, astro-ph.IM
Abstract

Characterizing the epoch of reionization (EoR) at z 6 via the redshifted 21 cm line of neutral Hydrogen (H i) 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 H i 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 "1σ"upper limits on the IGM brightness temperature to be ≤ 316 "pseudo"mK at κ =0.33 "pseudo"h Mpc-1 (data-limited) and ≤ 1000 "pseudo"mK at κ =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 H i signal from the foregrounds is similar to that in standard approaches, and the power spectrum of the bispectrum phase is still data-limited (at 106 dynamic range) indicating scope for further improvement in sensitivity as the array build-out continues.

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. Erratum: PAPER-64 constraints on reionization: The 21 cm power spectrum at z = 8.4 (Astrophysical Journal (2015) 809 (61) DOI: 10.1088/0004-637X/809/1/61)

Author

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

Subjects
Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry, Astronomy & Astrophysics, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural)
Abstract

In this erratum, we retract the upper limits on the 21 cm power spectrum presented in the published article. The published article reported an upper limit on δ 212(k ) of (22.4 mK)2 at z= 8.4 in the range 0.15 < k < 0.5h Mpc-1. This analysis underestimated the level of signal loss, or attenuation of the target cosmological 21 cm signal associated with the chosen power spectrum estimator, and also underestimated the statistical error on those estimates. A revised result, with a new analysis, is presented in M. K. Kolopanis et al. (2018, in preparation). Below, we briefly summarize the errors in the original analysis and how they are corrected. For an indepth analysis and discussion of the errors, we refer the reader to Cheng et al. (2018). Signal loss was expected in the original analysis because the covariance matrices, C, used to weight the un-normalized bandpower estimates, qa, in (Formula Presented) were empirically estimated from a time-averaged finite ensemble of the data, x, such that (Formula Presented). While the true covariance C leads to an inherently unbiased lossless estimator of the power spectrum, using an empirically estimated Ĉ can lead to signal loss. Specifically, weighting data by an empirically estimated covariance carries the risk of overfitting and downweighting EoR fluctuations that are coupled to the data. In Cheng et al. (2018), it is shown that these couplings are especially strong in the fringe-rate filtered PAPER-64 data set. The first and most impactful error relates to the method by which signal loss was estimated. To assess signal loss from the empirically estimated covariance matrix, different realizations of mock cosmological signals e of known amplitudes are added to the original data to form a new data vector, (Formula Presented). New covariance matrices, (Formula Presented) are used to estimate un-normalized bandpowers (Formula Presented), which can be written as (Formula Presented). The normalized power estimate can then be compared to the known injected power in e to estimate signal loss. The key error in the previous analysis was to assume that, since e was statistically independent of x, that the two middle crossterms in Equation (2) would average to zero in an ensemble. However, as shown in Cheng et al. (2018) and Switzer et al. (2015), these cross-terms can contain significant negative power because Ĉr contains information that correlates the two vectors. Ignoring these cross-terms leads to a significant underestimate of signal loss. As a result, we presented negligible signal loss in our original analysis, when in fact approximately 99.99% of the signal was removed (Cheng et al. 2018). Correcting for the actual signal loss is the biggest factor revising the upper limit on 21 D2 . The second mistake made in the original analysis was to underestimate the statistical errors in the reported power spectrum estimates. The original analysis used a bootstrap resampling technique on power spectral measurements over the baseline and time axes. However, fringe-rate filtering introduces significant correlations in the data along the time axis. As is discussed in Cheng et al. (2018), bootstrapping across correlated samples can result in a significant underestimate of the variation in the data if the number of resamplings is not equal to the number of independent samples in the data, as in the case of the original analysis. The error bars associated with this oversampling were underestimated by approximately a factor of 2 (in mK). The revised analysis in M. K. Kolopanis et al. (2018, in preparation) only applies bootstrap resampling across the baseline axis to avoid this problem. The mistake in estimating the statistical errors should have become apparent when comparing results to our theoretical thermal noise sensitivity. Unfortunately, a third miscalculation was made in estimating the thermal noise sensitivity. As detailed in Cheng et al. (2018), this miscalculation stemmed from numerous small mismatches between the idealized analysis pipeline used to estimate sensitivity and the actual analysis applied to the data. As a result, our estimated thermal noise sensitivity was approximately a factor of 3 low (in mK), leading to the mistaken impression that our error bars were consistent with the level of thermal noise. In summary, we retract the power spectrum results shown in Figures 18 and 20 in the published article. Results that relied on the original limits, including those presented in Figure 21, are retracted. Additionally, the companion paper to the original manuscript, Pober et al. (2015), used the original limits to place constraints on the spin temperature of the intergalactic medium (IGM) at z=8.4. Our revised limits do not place significant constraints on the IGM temperature, and the results of Figure 4 from Pober et al. (2015) should be disregarded. However, we note that their analysis would still be relevant should a future experiment place constraints on the 21 cm signal similar to those claimed in the published article. An updated analysis of this same data set is presented in M. K. Kolopanis et al. (2018, in preparation), where these revised results are put into context with measurements at other redshifts.

Published
2018

7. Polarized redundant-baseline calibration for 21 cm cosmology without adding spectral structure

Author

Dillon, JS, Kohn, SA, Parsons, AR, Aguirre, JE, Ali, ZS, Bernardi, G, Kern, NS, Li, W, Liu, A, Nunhokee, CD, and Pober, JC

Subjects
instrumentation: interferometers, dark ages, reionization, first stars, dark ages, reionization, first stars, Astronomy & Astrophysics, Astronomical and Space Sciences
Abstract

21 cm cosmology is a promising new probe of the evolution of visible matter in our universe, especially during the poorly constrained Cosmic Dawn and Epoch of Reionization. However, in order to separate the 21 cm signal from bright astrophysical foregrounds, we need an exquisite understanding of our telescopes so as to avoid adding spectral structure to spectrally smooth foregrounds. One powerful calibration method relies on repeated simultaneous measurements of the same interferometric baseline to solve for the sky signal and for instrumental parameters simultaneously. However, certain degrees of freedom are not constrained by asserting internal consistency between redundant measurements. In this paper, we review the origin of these degeneracies of redundant-baseline calibration and demonstrate how they can source unwanted spectral structure in our measurement and show how to eliminate that additional, artificial structure. We also generalize redundant calibration to dual-polarization instruments, derive the degeneracy structure, and explore the unique challenges to calibration and preserving spectral smoothness presented by a polarized measurement.

Published
2018

8. 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

9. 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

10. PAPER-64 CONSTRAINTS on REIONIZATION: The 21 cm POWER SPECTRUM at z = 8.4

Author

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

Subjects
cosmology: observations, dark ages, reionization, first stars, early universe, instrumentation: interferometers, 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

In this paper, we report new limits on 21 cm emission from cosmic reionization based on a 135 day observing campaign with a 64-element deployment of the Donald C. Backer Precision Array for Probing the Epoch of Reionization in South Africa. This work extends the work presented in Parsons et al. with more collecting area, a longer observing period, improved redundancy-based calibration, improved fringe-rate filtering, and updated power-spectral analysis using optimal quadratic estimators. The result is a new 2σ upper limit on Δ2(k) of (22.4 mK)2 in the range < k < 0.5h Mpc-1 at z = 8.4. This represents a three-fold improvement over the previous best upper limit. As we discuss in more depth in a forthcoming paper, this upper limit supports and extends previous evidence against extremely cold reionization scenarios. We conclude with a discussion of implications for future 21 cm reionization experiments, including the newly funded Hydrogen Epoch of Reionization Array.

Published
2015

11. Direct Optimal Mapping for 21cm Cosmology: A Demonstration with the Hydrogen Epoch of Reionization Array

Author

Xu, Z, Hewitt, JN, Chen, KF, Kim, H, Dillon, JS, Kern, NS, Morales, MF, Hazelton, BJ, Byrne, R, Fagnoni, N, Acedo, EDL, Abdurashidova, Z, Adams, T, Aguirre, JE, Alexander, P, Ali, ZS, Baartman, R, Balfour, Y, Beardsley, AP, Bernardi, G, Billings, TS, Bowman, JD, Bradley, RF, Bull, P, Burba, J, Carey, S, Carilli, CL, Cheng, C, DeBoer, DR, Dexter, M, Eksteen, N, Ely, J, Ewall-Wice, A, Fritz, R, Furlanetto, Gale-Sides, K, Glendenning, B, Gorthi, D, Greig, B, Grobbelaar, J, Halday, Z, Hickish, J, Jacobs, DC, Julius, A, Kariseb, M, Kerrigan, J, Kittiwisit, P, Kohn, SA, Kolopanis, M, Lanman, A, Plante, PL, Liu, A, Loots, A, Ma, YZ, Edward MacMahon, DH, Malan, L, Malgas, C, Malgas, K, Marero, B, Martinot, ZE, Mesinger, A, Molewa, M, Mosiane, T, Murray, SG, Neben, AR, Nikolic, B, Nuwegeld, H, Parsons, AR, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Robnett, J, Rosie, K, Sims, P, Smith, C, Swarts, H, Thyagarajan, N, Wyngaarden, PVV, Williams, PKG, Zheng, H, Xu, Z [0000-0001-5112-2567], Hewitt, JN [0000-0002-4117-570X], Chen, KF [0000-0002-3839-0230], Dillon, JS [0000-0003-3336-9958], Kern, NS [0000-0002-8211-1892], Morales, MF [0000-0001-7694-4030], Hazelton, BJ [0000-0001-7532-645X], Byrne, R [0000-0003-4980-2736], Aguirre, JE [0000-0002-4810-666X], Beardsley, AP [0000-0001-9428-8233], Bernardi, G [0000-0002-0916-7443], Bowman, JD [0000-0002-8475-2036], Bradley, RF [0000-0003-1172-8331], Bull, P [0000-0001-5668-3101], Carilli, CL [0000-0001-6647-3861], DeBoer, DR [0000-0003-3197-2294], Ewall-Wice, A [0000-0002-0086-7363], Furlanetto, SR [0000-0002-0658-1243], Gorthi, D [0000-0002-0829-167X], Greig, B [0000-0002-4085-2094], Jacobs, DC [0000-0002-0917-2269], Kerrigan, J [0000-0002-1876-272X], Kittiwisit, P [0000-0003-0953-313X], Kohn, SA [0000-0001-6744-5328], Kolopanis, M [0000-0002-2950-2974], Lanman, A [0000-0003-2116-3573], Plante, PL [0000-0002-4693-0102], Liu, A [0000-0001-6876-0928], Ma, YZ [0000-0001-8108-0986], Mesinger, A [0000-0003-3374-1772], Murray, SG [0000-0003-3059-3823], Neben, AR [0000-0001-7776-7240], Parsons, AR [0000-0002-5400-8097], Patra, N [0000-0002-9457-1941], Pober, JC [0000-0002-3492-0433], Sims, P [0000-0002-2871-0413], Thyagarajan, N [0000-0003-1602-7868], Williams, PKG [0000-0003-3734-3587], Apollo - University of Cambridge Repository, Xu, Zhilei, Hewitt, Jacqueline N., Chen, Kai-Feng, Kim, Honggeun, Dillon, Joshua S., Kern, Nicholas S., Morales, Miguel F., Hazelton, Bryna J., Byrne, Ruby, Fagnoni, Nicola, de Lera Acedo, Eloy, Abdurashidova, Zara, Adams, Tyrone, Aguirre, James E., Alexander, Paul, Ali, Zaki S., Baartman, Rushelle, Balfour, Yanga, Beardsley, Adam P., Bernardi, Gianni, Billings, Tashalee S., Bowman, Judd D., Bradley, Richard F., Bull, Philip, Burba, Jacob, Carey, Steven, Carilli, Chris L., Cheng, Carina, Deboer, David R., Dexter, Matt, Eksteen, Nico, Ely, John, Ewall-Wice, Aaron, Fritz, Randall, Furlanetto, Steven R., Gale-Sides, Kingsley, Glendenning, Brian, Gorthi, Deepthi, Greig, Bradley, Grobbelaar, Jasper, Halday, Ziyaad, Hickish, Jack, Jacobs, Daniel C., Julius, Austin, Kariseb, Maccalvin, Kerrigan, Joshua, Kittiwisit, Piyanat, Kohn, Saul A., Kolopanis, Matthew, Lanman, Adam, La Plante, Paul, Liu, Adrian, Loots, Anita, Ma, Yin-Zhe, Harold Edward MacMahon, David, Malan, Lourence, Malgas, Cresshim, Malgas, Keith, Marero, Bradley, Martinot, Zachary E., Mesinger, ANDREI ALBERT, Molewa, Mathakane, Mosiane, Tshegofalang, Murray, Steven G., Neben, Abraham R., Nikolic, Bojan, Nuwegeld, Han, Parsons, Aaron R., Patra, Nipanjana, Pieterse, Samantha, Pober, Jonathan C., Razavi-Ghods, Nima, Robnett, Jame, Rosie, Kathryn, Sims, Peter, Smith, Craig, Swarts, Hilton, Thyagarajan, Nithyanandan, Van Van Wyngaarden, Pieter, Williams, Peter K. G., and Zheng, Haoxuan

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), model, maps, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Galactic radio-emission, 5109 Space Sciences, power spectrum, calibration, 10 mhz, Settore FIS/05 - Astronomia e Astrofisica, 5101 Astronomical Sciences, Space and Planetary Science, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), upper limit, 51 Physical Sciences, 5107 Particle and High Energy Physics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Motivated by the desire for wide-field images with well-defined statistical properties for 21cm cosmology, we implement an optimal mapping pipeline that computes a maximum likelihood estimator for the sky using the interferometric measurement equation. We demonstrate this direct optimal mapping with data from the Hydrogen Epoch of Reionization (HERA) Phase I observations. After validating the pipeline with simulated data, we develop a maximum likelihood figure-of-merit for comparing four sky models at 166MHz with a bandwidth of 100kHz. The HERA data agree with the GLEAM catalogs to, 16 pages, 10 figures, 2 tables, published on ApJ

Published
2022

12. Automated Detection of Antenna Malfunctions in Large-N Interferometers: A case study With the Hydrogen Epoch of Reionization Array

Author

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

Published
2022

13. Effects of model incompleteness on the drift-scan calibration of radio telescopes

Author

Gehlot, BK, Jacobs, DC, Bowman, JD, Mahesh, N, Murray, SG, Kolopanis, M, Beardsley, AP, Abdurashidova, Z, Aguirre, JE, Alexander, P, Ali, ZS, Balfour, Y, Bernardi, G, Billings, TS, Bradley, RF, Bull, P, Burba, J, Carey, S, Carilli, CL, Cheng, C, DeBoer, DR, Dexter, M, Acedo, EDL, Dillon, JS, 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, Julius, A, Kern, NS, Kerrigan, J, Kittiwisit, P, Kohn, SA, Lanman, A, La Plante, P, Lekalake, T, Lewis, D, Liu, A, Ma, Y-Z, MacMahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Matsetela, E, Mesinger, A, Molewa, M, Monsalve, RA, Morales, MF, Mosiane, T, Neben, AR, Nikolic, B, Parsons, AR, 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, Zheng, H, Gehlot, BK, Jacobs, DC, Bowman, JD, Mahesh, N, Murray, SG, Kolopanis, M, Beardsley, AP, Abdurashidova, Z, Aguirre, JE, Alexander, P, Ali, ZS, Balfour, Y, Bernardi, G, Billings, TS, Bradley, RF, Bull, P, Burba, J, Carey, S, Carilli, CL, Cheng, C, DeBoer, DR, Dexter, M, Acedo, EDL, Dillon, JS, 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, Julius, A, Kern, NS, Kerrigan, J, Kittiwisit, P, Kohn, SA, Lanman, A, La Plante, P, Lekalake, T, Lewis, D, Liu, A, Ma, Y-Z, MacMahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Matsetela, E, Mesinger, A, Molewa, M, Monsalve, RA, Morales, MF, Mosiane, T, Neben, AR, Nikolic, B, Parsons, AR, 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

Abstract

Precision calibration poses challenges to experiments probing the redshifted 21-cm signal of neutral hydrogen from the Cosmic Dawn and Epoch of Reionization (z ∼ 30–6). In both interferometric and global signal experiments, systematic calibration is the leading source of error. Though many aspects of calibration have been studied, the overlap between the two types of instruments has received less attention. We investigate the sky based calibration of total power measurements with a HERA dish and an EDGES-style antenna to understand the role of autocorrelations in the calibration of an interferometer and the role of sky in calibrating a total power instrument. Using simulations we study various scenarios such as time variable gain, incomplete sky calibration model, and primary beam model. We find that temporal gain drifts, sky model incompleteness, and beam inaccuracies cause biases in the receiver gain amplitude and the receiver temperature estimates. In some cases, these biases mix spectral structure between beam and sky resulting in spectrally variable gain errors. Applying the calibration method to the HERA and EDGES data, we find good agreement with calibration via the more standard methods. Although instrumental gains are consistent with beam and sky errors similar in scale to those simulated, the receiver temperatures show significant deviations from expected values. While we show that it is possible to partially mitigate biases due to model inaccuracies by incorporating a time-dependent gain model in calibration, the resulting errors on calibration products are larger and more correlated. Completely addressing these biases will require more accurate sky and primary beam models.

Published
2021

14. A Real Time Processing system for big data in astronomy: Applications to HERA

Author

La Plante, P, Williams, PKG, Kolopanis, M, Dillon, JS, Beardsley, AP, Kern, NS, Wilensky, M, Ali, ZS, 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, Acedo, EDL, 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, Lanman, A, Lekalake, T, Lewis, D, Liu, A, 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, Parsons, AR, 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, Thyagarajan, N, Zheng, H, La Plante, P, Williams, PKG, Kolopanis, M, Dillon, JS, Beardsley, AP, Kern, NS, Wilensky, M, Ali, ZS, 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, Acedo, EDL, 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, Lanman, A, Lekalake, T, Lewis, D, Liu, A, 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, Parsons, AR, 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, Thyagarajan, N, and Zheng, H

Published
2021

15. 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
Full Text
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16. Imaging and Modeling Data from the Hydrogen Epoch of Reionization Array

Author

Carilli, CL, Thyagarajan, N, Kent, J, Nikolic, B, Gale-Sides, K, Kern, NS, Bernardi, G, Mesinger, A, Matika, S, Abdurashidova, Z, Aguirre, JE, Alexander, P, Ali, ZS, Balfour, Y, Beardsley, AP, Billings, TS, Bowman, JD, Bradley, RF, Bull, P, Burba, J, Cheng, C, Deboer, DR, Dexter, M, Acedo, EDL, Dillon, JS, Ewall-Wice, A, Fagnoni, N, Fritz, R, Furlanetto, SR, Glendenning, B, Gorthi, D, Greig, B, Grobbelaar, J, Halday, Z, Hazelton, BJ, Hewitt, JN, Hickish, J, Jacobs, DC, Josaitis, A, Julius, A, 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, Molewa, M, Morales, MF, Mosiane, T, Neben, AR, Parra, JM, Parsons, AR, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Robnett, J, Rosie, K, Sims, P, Syce, A, Williams, PKG, Zheng, H, Carilli, CL, Thyagarajan, N, Kent, J, Nikolic, B, Gale-Sides, K, Kern, NS, Bernardi, G, Mesinger, A, Matika, S, Abdurashidova, Z, Aguirre, JE, Alexander, P, Ali, ZS, Balfour, Y, Beardsley, AP, Billings, TS, Bowman, JD, Bradley, RF, Bull, P, Burba, J, Cheng, C, Deboer, DR, Dexter, M, Acedo, EDL, Dillon, JS, Ewall-Wice, A, Fagnoni, N, Fritz, R, Furlanetto, SR, Glendenning, B, Gorthi, D, Greig, B, Grobbelaar, J, Halday, Z, Hazelton, BJ, Hewitt, JN, Hickish, J, Jacobs, DC, Josaitis, A, Julius, A, 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, Molewa, M, Morales, MF, Mosiane, T, Neben, AR, Parra, JM, Parsons, AR, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Robnett, J, Rosie, K, Sims, P, Syce, A, Williams, PKG, and Zheng, H

Abstract

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.

Published
2020

17. Mitigating Internal Instrument Coupling for 21 cm Cosmology. II. A Method Demonstration with the Hydrogen Epoch of Reionization Array

Author

Kern, NS, Parsons, AR, Dillon, JS, Lanman, AE, Liu, A, Bull, P, Ewall-Wice, A, Abdurashidova, Z, Aguirre, JE, 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, Fagnoni, N, Fritz, R, Furlanetto, SR, 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, La Plante, P, Lekalake, T, Macmahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Matsetela, E, Mesinger, A, Molewa, M, Morales, MF, Mosiane, T, Murray, SG, Neben, AR, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Ringuette, J, Robnett, J, Rosie, K, Sims, P, Smith, C, Syce, A, Thyagarajan, N, Williams, PKG, Zheng, H, Kern, NS, Parsons, AR, Dillon, JS, Lanman, AE, Liu, A, Bull, P, Ewall-Wice, A, Abdurashidova, Z, Aguirre, JE, 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, Fagnoni, N, Fritz, R, Furlanetto, SR, 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, La Plante, P, Lekalake, T, Macmahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Matsetela, E, Mesinger, A, Molewa, M, Morales, MF, Mosiane, T, Murray, SG, Neben, AR, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Ringuette, J, Robnett, J, Rosie, K, Sims, P, Smith, C, Syce, A, Thyagarajan, N, Williams, PKG, and Zheng, H

Abstract

We present a study of internal reflection and cross-coupling systematics in Phase I of the Hydrogen Epoch of Reionization Array (HERA). In a companion paper, we outlined the mathematical formalism for such systematics and presented algorithms for modeling and removing them from the data. In this work, we apply these techniques to data from HERA's first observing season as a method demonstration. The data show evidence for systematics that, without removal, would hinder a detection of the 21 cm power spectrum for the targeted Epoch of Reionization (EoR) line-of-sight modes in the range 0.2 h Mpc < $" SRC="apjab5e8aieqn1.gif"/ < 0.5 h Mpc . In particular, we find evidence for nonnegligible amounts of spectral structure in the raw autocorrelations that overlaps with the EoR window and is suggestive of complex instrumental effects. Through systematic modeling on a single night of data, we find we can recover these modes in the power spectrum down to the integrated noise floor, achieving a dynamic range in the EoR window of 10 in power (mK units) with respect to the bright galactic foreground signal. Future work with deeper integrations will help determine whether these systematics can continue to be mitigated down to EoR levels. For future observing seasons, HERA will have upgraded analog and digital hardware to better control these systematics in the field. -1 -1 -1 -1 6 2

Published
2020

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

Author

Kern, NS, Dillon, JS, Parsons, AR, Carilli, CL, Bernardi, G, Abdurashidova, Z, Aguirre, JE, Alexander, P, Ali, ZS, Balfour, Y, Beardsley, AP, Billings, TS, Bowman, JD, Bradley, RF, Bull, P, Burba, J, Carey, S, 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, La Plante, P, Lekalake, T, Liu, A, Macmahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Matsetela, E, Mesinger, A, Molewa, M, Morales, MF, Mosiane, T, Murray, SG, Neben, AR, Nikolic, B, Nunhokee, CD, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Ringuette, J, Robnett, J, Rosie, K, Sims, P, Smith, C, Syce, A, Thyagarajan, N, Williams, PKG, Zheng, H, Kern, NS, Dillon, JS, Parsons, AR, Carilli, CL, Bernardi, G, Abdurashidova, Z, Aguirre, JE, Alexander, P, Ali, ZS, Balfour, Y, Beardsley, AP, Billings, TS, Bowman, JD, Bradley, RF, Bull, P, Burba, J, Carey, S, 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, La Plante, P, Lekalake, T, Liu, A, Macmahon, D, Malan, L, Malgas, C, Maree, M, Martinot, ZE, Matsetela, E, Mesinger, A, Molewa, M, Morales, MF, Mosiane, T, Murray, SG, Neben, AR, Nikolic, B, Nunhokee, CD, Patra, N, Pieterse, S, Pober, JC, Razavi-Ghods, N, Ringuette, J, Robnett, J, Rosie, K, Sims, P, Smith, C, Syce, A, Thyagarajan, N, Williams, PKG, and Zheng, H

Abstract

We discuss absolute calibration strategies for Phase I of the Hydrogen Epoch of Reionization Array (HERA), which aims to measure the cosmological 21 cm signal from the Epoch of Reionization. HERA is a drift-scan array with a 10° wide field of view, meaning bright, well-characterized point-source transits are scarce. This, combined with HERA's redundant sampling of the uv plane and the modest angular resolution of the Phase I instrument, make traditional sky-based and self-calibration techniques difficult to implement with high dynamic range. Nonetheless, in this work, we demonstrate calibration for HERA using point-source catalogs and electromagnetic simulations of its primary beam. We show that unmodeled diffuse flux and instrumental contaminants can corrupt the gain solutions and present a gain-smoothing approach for mitigating their impact on the 21 cm power spectrum. We also demonstrate a hybrid sky and redundant calibration scheme and compare it to pure sky-based calibration, showing only a marginal improvement to the gain solutions at intermediate delay scales. Our work suggests that the HERA Phase I system can be well calibrated for a foreground avoidance power spectrum estimator by applying direction-independent gains with a small set of degrees of freedom across the frequency and time axes.

Published
2020

19. H <scp>I</scp>21-cm Cosmology and the Bispectrum: Closure Diagnostics in Massively Redundant Interferometric Arrays

Author

Carilli, CL, Nikolic, B, Thyagarajan, N, Gale-Sides, K, Abdurashidova, Z, Aguirre, JE, Alexander, P, Ali, ZS, Balfour, Y, Beardsley, AP, Bernardi, G, Bowman, JD, Bradley, RF, Burba, J, Cheng, C, DeBoer, DR, Dexter, M, Acedo, EDL, Dillon, JS, Ewall-Wice, A, Fadana, G, Fagnoni, N, Fritz, R, Furlanetto, SR, Ghosh, A, Glendenning, B, Greig, B, Grobbelaar, J, Halday, Z, Hazelton, BJ, Hewitt, JN, Hickish, J, Jacobs, DC, Julius, A, Kariseb, M, Kohn, SA, Kolopanis, M, Lekalake, T, Liu, A, Loots, A, MacMahon, D, Malan, L, Malgas, C, Maree, M, Martinot, Z, Matsetela, E, Mesinger, A, Molewa, M, Morales, MF, Neben, AR, Parsons, AR, Patra, N, Pieterse, S, Plante, PL, Pober, JC, Razavi-Ghods, N, Ringuette, J, Robnett, J, Rosie, K, Sell, R, Sims, P, Smith, C, Syce, A, Williams, PKG, and Zheng, H

Subjects
Physics, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Phase (waves), Closure (topology), FOS: Physical sciences, Condensed Matter Physics, 01 natural sciences, Computational physics, Interferometry, 0103 physical sciences, Closure phase, Redundancy (engineering), General Earth and Planetary Sciences, Electrical and Electronic Engineering, Allan variance, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Reionization, Bispectrum, astro-ph.IM
Abstract

New massively redundant low frequency arrays allow for a novel investigation of closure relations in interferometry. We employ commissioning data from the Hydrogen Epoch of Reionization Array to investigate closure quantities in this densely packed grid array of 14m antennas operating at 100 MHz to 200 MHz. We investigate techniques that utilize closure phase spectra for redundant triads to estimate departures from redundancy for redundant baseline visibilities. We find a median absolute deviation from redundancy in closure phase across the observed frequency range of about 4.5deg. This value translates into a non-redundancy per visibility phase of about 2.6deg, using prototype electronics. The median absolute deviations from redundancy decrease with longer baselines. We show that closure phase spectra can be used to identify ill-behaved antennas in the array, independent of calibration. We investigate the temporal behavior of closure spectra. The Allan variance increases after a one minute stride time, due to passage of the sky through the primary beam of the transit telescope. However, the closure spectra repeat to well within the noise per measurement at corresponding local sidereal times (LST) from day to day. In future papers in this series we will develop the technique of using closure phase spectra in the search for the HI 21cm signal from cosmic reionization., 32 pages. 11 figures. Accepted to Radio Science

Published
2018

20. Polarized Foreground Power Spectra from the HERA-19 Commissioning Array

Author

Kohn, S, Chichura, PM, Igarashi, AS, Fortino, AF, Aguirre, JE, Benefo, RK, Billings, TS, Gallardo, S, Plante, PL, Martinot, ZE, Nunhokee, CD, 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, Kern, NS, Kolopanis, M, Lekalake, T, Liu, A, 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
Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics, 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 inherent spectral smoothness of synchrotron radiation, the dominant foreground emission mechanism, and the chromaticity of the instrument allows these experiments to delineate a boundary between spectrally smooth and structured emission in Fourier space (the "wedge" or "pitchfork", and the "EoR Window", respectively). 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 Hydrogen Epoch of Reionization Array (HERA) 19-element commissioning array, we investigate the polarization response of this new instrument in the power spectrum domain. We confirm the expected structure of foreground emission in Fourier space predicted by Thyagarajan et al. (2015a, 2016) for a HERA-type dish, and detect polarized power within the pitchfork. Using simulations of the polarized response of HERA feeds, we find that almost all of the power in Stokes Q, U and V can be attributed to instrumental leakage effects. Power consistent with noise in the EoR window suggests a negligible amount of spectrally-structured polarized power, to the noise-levels attained. This lends confidence to deep integrations with HERA in the future, but with a lower noise floor these future studies will also have to investigate their polarized response.

Published
2018

21. Spectral Energy Distribution and Radio Halo of NGC 253 at Low Radio Frequencies

Author

Kapińska, AD, Staveley-Smith, L, Crocker, R, Meurer, GR, Bhandari, S, Hurley-Walker, N, Offringa, AR, Hanish, DJ, Seymour, N, Ekers, RD, Bell, ME, Callingham, JR, Dwarakanath, KS, For, BQ, Gaensler, BM, Hancock, PJ, Hindson, L, Johnston-Hollitt, M, Lenc, E, McKinley, B, Morgan, J, Procopio, P, Wayth, RB, Wu, C, Zheng, Q, Barry, N, Beardsley, AP, Bowman, JD, Briggs, F, Carroll, P, Dillon, JS, Ewall-Wice, A, Feng, L, Greenhill, LJ, Hazelton, BJ, Hewitt, JN, Jacobs, DJ, Kim, HS, Kittiwisit, P, Line, J, Loeb, A, Mitchell, DA, Morales, MF, Neben, AR, Paul, S, Pindor, B, Pober, JC, Riding, J, Sethi, SK, Shankar, NU, Subrahmanyan, R, Sullivan, IS, Tegmark, M, Thyagarajan, N, Tingay, SJ, Trott, CM, Webster, RL, Wyithe, SB, Cappallo, RJ, Deshpande, AA, Kaplan, DL, Lonsdale, CJ, McWhirter, SR, Morgan, E, Oberoi, D, Ord, SM, Prabu, T, Srivani, KS, Williams, A, Williams, CL, Kapińska, AD, Staveley-Smith, L, Crocker, R, Meurer, GR, Bhandari, S, Hurley-Walker, N, Offringa, AR, Hanish, DJ, Seymour, N, Ekers, RD, Bell, ME, Callingham, JR, Dwarakanath, KS, For, BQ, Gaensler, BM, Hancock, PJ, Hindson, L, Johnston-Hollitt, M, Lenc, E, McKinley, B, Morgan, J, Procopio, P, Wayth, RB, Wu, C, Zheng, Q, Barry, N, Beardsley, AP, Bowman, JD, Briggs, F, Carroll, P, Dillon, JS, Ewall-Wice, A, Feng, L, Greenhill, LJ, Hazelton, BJ, Hewitt, JN, Jacobs, DJ, Kim, HS, Kittiwisit, P, Line, J, Loeb, A, Mitchell, DA, Morales, MF, Neben, AR, Paul, S, Pindor, B, Pober, JC, Riding, J, Sethi, SK, Shankar, NU, Subrahmanyan, R, Sullivan, IS, Tegmark, M, Thyagarajan, N, Tingay, SJ, Trott, CM, Webster, RL, Wyithe, SB, Cappallo, RJ, Deshpande, AA, Kaplan, DL, Lonsdale, CJ, McWhirter, SR, Morgan, E, Oberoi, D, Ord, SM, Prabu, T, Srivani, KS, Williams, A, and Williams, CL

Abstract

© 2017. The American Astronomical Society. All rights reserved. We present new radio continuum observations of NGC 253 from the Murchison Widefield Array at frequencies between 76 and 227 MHz. We model the broadband radio spectral energy distribution for the total flux density of NGC 253 between 76 MHz and 11 GHz. The spectrum is best described as a sum of a central starburst and extended emission. The central component, corresponding to the inner 500 pc of the starburst region of the galaxy, is best modeled as an internally free-free absorbed synchrotron plasma, with a turnover frequency around 230 MHz. The extended emission component of the spectrum of NGC 253 is best described as a synchrotron emission flattening at low radio frequencies. We find that 34% of the extended emission (outside the central starburst region) at 1 GHz becomes partially absorbed at low radio frequencies. Most of this flattening occurs in the western region of the southeast halo, and may be indicative of synchrotron self-absorption of shock-reaccelerated electrons or an intrinsic low-energy cutoff of the electron distribution. Furthermore, we detect the large-scale synchrotron radio halo of NGC 253 in our radio images. At 154-231 MHz the halo displays the well known X-shaped/horn-like structure, and extends out to ∼8 kpc in the z-direction (from the major axis).

Published
2017

22. FOREGROUNDS IN WIDE-FIELD REDSHIFTED 21 cm POWER SPECTRA

Author

Thyagarajan, N, Jacobs, DC, Bowman, JD, Barry, N, Beardsley, AP, Bernardi, G, Briggs, F, Cappallo, RJ, Carroll, P, Corey, BE, de Oliveira-Costa, A, Dillon, JS, Emrich, D, Ewall-Wice, A, Feng, L, Goeke, R, Greenhill, LJ, Hazelton, BJ, Hewitt, JN, Hurley-Walker, N, Johnston-Hollitt, M, Kaplan, DL, Kasper, JC, Kim, H-S, Kittiwisit, P, Kratzenberg, E, Lenc, E, Line, J, Loeb, A, Lonsdale, CJ, Lynch, MJ, McKinley, B, McWhirter, SR, Mitchell, DA, Morales, MF, Morgan, E, Neben, AR, Oberoi, D, Offringa, AR, Ord, SM, Paul, S, Pindor, B, Pober, JC, Prabu, T, Procopio, P, Riding, J, Rogers, AEE, Roshi, A, Shankar, NU, Sethi, SK, Srivani, KS, Subrahmanyan, R, Sullivan, IS, Tegmark, M, Tingay, SJ, Trott, CM, Waterson, M, Wayth, RB, Webster, RL, Whitney, AR, Williams, A, Williams, CL, Wu, C, Wyithe, JSB, Thyagarajan, N, Jacobs, DC, Bowman, JD, Barry, N, Beardsley, AP, Bernardi, G, Briggs, F, Cappallo, RJ, Carroll, P, Corey, BE, de Oliveira-Costa, A, Dillon, JS, Emrich, D, Ewall-Wice, A, Feng, L, Goeke, R, Greenhill, LJ, Hazelton, BJ, Hewitt, JN, Hurley-Walker, N, Johnston-Hollitt, M, Kaplan, DL, Kasper, JC, Kim, H-S, Kittiwisit, P, Kratzenberg, E, Lenc, E, Line, J, Loeb, A, Lonsdale, CJ, Lynch, MJ, McKinley, B, McWhirter, SR, Mitchell, DA, Morales, MF, Morgan, E, Neben, AR, Oberoi, D, Offringa, AR, Ord, SM, Paul, S, Pindor, B, Pober, JC, Prabu, T, Procopio, P, Riding, J, Rogers, AEE, Roshi, A, Shankar, NU, Sethi, SK, Srivani, KS, Subrahmanyan, R, Sullivan, IS, Tegmark, M, Tingay, SJ, Trott, CM, Waterson, M, Wayth, RB, Webster, RL, Whitney, AR, Williams, A, Williams, CL, Wu, C, and Wyithe, JSB

Abstract

Detection of 21~cm emission of HI from the epoch of reionization, at redshifts z>6, is limited primarily by foreground emission. We investigate the signatures of wide-field measurements and an all-sky foreground model using the delay spectrum technique that maps the measurements to foreground object locations through signal delays between antenna pairs. We demonstrate interferometric measurements are inherently sensitive to all scales, including the largest angular scales, owing to the nature of wide-field measurements. These wide-field effects are generic to all observations but antenna shapes impact their amplitudes substantially. A dish-shaped antenna yields the most desirable features from a foreground contamination viewpoint, relative to a dipole or a phased array. Comparing data from recent Murchison Widefield Array observations, we demonstrate that the foreground signatures that have the largest impact on the HI signal arise from power received far away from the primary field of view. We identify diffuse emission near the horizon as a significant contributing factor, even on wide antenna spacings that usually represent structures on small scales. For signals entering through the primary field of view, compact emission dominates the foreground contamination. These two mechanisms imprint a characteristic "pitchfork" signature on the "foreground wedge" in Fourier delay space. Based on these results, we propose that selective down-weighting of data based on antenna spacing and time can mitigate foreground contamination substantially by a factor ~100 with negligible loss of sensitivity.

Published
2015

23. The Low-Frequency Environment of the Murchison Widefield Array: Radio-Frequency Interference Analysis and Mitigation

Author

Offringa, AR, Wayth, RB, Hurley-Walker, N, Kaplan, DL, Barry, N, Beardsley, AP, Bell, ME, Bernardi, G, Bowman, JD, Briggs, F, Callingham, JR, Cappallo, RJ, Carroll, P, Deshpande, AA, Dillon, JS, Dwarakanath, KS, Ewall-Wice, A, Feng, L, For, B-Q, Gaensler, BM, Greenhill, LJ, Hancock, P, Hazelton, BJ, Hewitt, JN, Hindson, L, Jacobs, DC, Johnston-Hollitt, M, Kapinska, AD, Kim, H-S, Kittiwisit, P, Lenc, E, Line, J, Loeb, A, Lonsdale, CJ, McKinley, B, McWhirter, SR, Mitchell, DA, Morales, MF, Morgan, E, Morgan, J, Neben, AR, Oberoi, D, Ord, SM, Paul, S, Pindor, B, Pober, JC, Prabu, T, Procopio, P, Riding, J, Shankar, NU, Sethi, S, Srivani, KS, Staveley-Smith, L, Subrahmanyan, R, Sullivan, IS, Tegmark, M, Thyagarajan, N, Tingay, SJ, Trott, CM, Webster, RL, Williams, A, Williams, CL, Wu, C, Wyithe, JS, Zheng, Q, Offringa, AR, Wayth, RB, Hurley-Walker, N, Kaplan, DL, Barry, N, Beardsley, AP, Bell, ME, Bernardi, G, Bowman, JD, Briggs, F, Callingham, JR, Cappallo, RJ, Carroll, P, Deshpande, AA, Dillon, JS, Dwarakanath, KS, Ewall-Wice, A, Feng, L, For, B-Q, Gaensler, BM, Greenhill, LJ, Hancock, P, Hazelton, BJ, Hewitt, JN, Hindson, L, Jacobs, DC, Johnston-Hollitt, M, Kapinska, AD, Kim, H-S, Kittiwisit, P, Lenc, E, Line, J, Loeb, A, Lonsdale, CJ, McKinley, B, McWhirter, SR, Mitchell, DA, Morales, MF, Morgan, E, Morgan, J, Neben, AR, Oberoi, D, Ord, SM, Paul, S, Pindor, B, Pober, JC, Prabu, T, Procopio, P, Riding, J, Shankar, NU, Sethi, S, Srivani, KS, Staveley-Smith, L, Subrahmanyan, R, Sullivan, IS, Tegmark, M, Thyagarajan, N, Tingay, SJ, Trott, CM, Webster, RL, Williams, A, Williams, CL, Wu, C, Wyithe, JS, and Zheng, Q

Abstract

The Murchison Widefield Array is a new low-frequency interferometric radio telescope built in Western Australia at one of the locations of the future Square Kilometre Array. We describe the automated radio-frequency interference detection strategy implemented for the Murchison Widefield Array, which is based on the aoflagger platform, and present 72–231 MHz radio-frequency interference statistics from 10 observing nights. Radio-frequency interference detection removes 1.1% of the data. Radio-frequency interference from digital TV is observed 3% of the time due to occasional ionospheric or atmospheric propagation. After radio-frequency interference detection and excision, almost all data can be calibrated and imaged without further radio-frequency interference mitigation efforts, including observations within the FM and digital TV bands. The results are compared to a previously published Low-Frequency Array radio-frequency interference survey. The remote location of the Murchison Widefield Array results in a substantially cleaner radio-frequency interference environment compared to Low-Frequency Array’s radio environment, but adequate detection of radio-frequency interference is still required before data can be analysed. We include specific recommendations designed to make the Square Kilometre Array more robust to radio-frequency interference, including: the availability of sufficient computing power for radio-frequency interference detection; accounting for radio-frequency interference in the receiver design; a smooth band-pass response; and the capability of radio-frequency interference detection at high time and frequency resolution (second and kHz-scale respectively).

Published
2015

24. Empirical covariance modeling for 21 cm power spectrum estimation: A method demonstration and new limits from early Murchison Widefield Array 128-tile data

Author

Dillon, JS, Neben, AR, Hewitt, JN, Tegmark, M, Barry, N, Beardsley, AP, Bowman, JD, Briggs, F, Carroll, P, de Oliveira-Costa, A, Ewall-Wice, A, Feng, L, Greenhill, LJ, Hazelton, BJ, Hernquist, L, Hurley-Walker, N, Jacobs, DC, Kim, HS, Kittiwisit, P, Lenc, E, Line, J, Loeb, A, McKinley, B, Mitchell, DA, Morales, MF, Offringa, AR, Paul, S, Pindor, B, Pober, JC, Procopio, P, Riding, J, Sethi, S, Shankar, NU, Subrahmanyan, R, Sullivan, I, Thyagarajan, N, Tingay, SJ, Trott, C, Wayth, RB, Webster, RL, Wyithe, S, Bernardi, G, Cappallo, RJ, Deshpande, AA, Johnston-Hollitt, M, Kaplan, DL, Lonsdale, CJ, McWhirter, SR, Morgan, E, Oberoi, D, Ord, SM, Prabu, T, Srivani, KS, Williams, A, Williams, CL, Dillon, JS, Neben, AR, Hewitt, JN, Tegmark, M, Barry, N, Beardsley, AP, Bowman, JD, Briggs, F, Carroll, P, de Oliveira-Costa, A, Ewall-Wice, A, Feng, L, Greenhill, LJ, Hazelton, BJ, Hernquist, L, Hurley-Walker, N, Jacobs, DC, Kim, HS, Kittiwisit, P, Lenc, E, Line, J, Loeb, A, McKinley, B, Mitchell, DA, Morales, MF, Offringa, AR, Paul, S, Pindor, B, Pober, JC, Procopio, P, Riding, J, Sethi, S, Shankar, NU, Subrahmanyan, R, Sullivan, I, Thyagarajan, N, Tingay, SJ, Trott, C, Wayth, RB, Webster, RL, Wyithe, S, Bernardi, G, Cappallo, RJ, Deshpande, AA, Johnston-Hollitt, M, Kaplan, DL, Lonsdale, CJ, McWhirter, SR, Morgan, E, Oberoi, D, Ord, SM, Prabu, T, Srivani, KS, Williams, A, and Williams, CL

Abstract

The separation of the faint cosmological background signal from bright astrophysical foregrounds remains one of the most daunting challenges of mapping the high-redshift intergalactic medium with the redshifted 21 cm line of neutral hydrogen. Advances in mapping and modeling of diffuse and point source foregrounds have improved subtraction accuracy, but no subtraction scheme is perfect. Precisely quantifying the errors and error correlations due to missubtracted foregrounds allows for both the rigorous analysis of the 21 cm power spectrum and for the maximal isolation of the "EoR window" from foreground contamination. We present a method to infer the covariance of foreground residuals from the data itself in contrast to previous attempts at a priori modeling. We demonstrate our method by setting limits on the power spectrum using a 3 h integration from the 128-tile Murchison Widefield Array. Observing between 167 and 198 MHz, we find at 95% confidence a best limit of Delta^2(k) < 3.7 x 10^4 mK^2 at comoving scale k = 0.18 hMpc^-1 and at z = 6.8, consistent with existing limits.

Published
2015

25. CONFIRMATION OF WIDE-FIELD SIGNATURES IN REDSHIFTED 21 cm POWER SPECTRA

Author

Thyagarajan, N, Jacobs, DC, Bowman, JD, Barry, N, Beardsley, AP, Bernardi, G, Briggs, F, Cappallo, RJ, Carroll, P, Deshpande, AA, de Oliveira-Costa, A, Dillon, JS, Ewall-Wice, A, Feng, L, Greenhill, LJ, Hazelton, BJ, Hernquist, L, Hewitt, JN, Hurley-Walker, N, Johnston-Hollitt, M, Kaplan, DL, Kim, H-S, Kittiwisit, P, Lenc, E, Line, J, Loeb, A, Lonsdale, CJ, McKinley, B, McWhirter, SR, Mitchell, DA, Morales, MF, Morgan, E, Neben, AR, Oberoi, D, Offringa, AR, Ord, SM, Paul, S, Pindor, B, Pober, JC, Prabu, T, Procopio, P, Riding, J, Shankar, NU, Sethi, SK, Srivani, KS, Subrahmanyan, R, Sullivan, IS, Tegmark, M, Tingay, SJ, Trott, CM, Wayth, RB, Webster, RL, Williams, A, Williams, CL, Wyithe, JSB, Thyagarajan, N, Jacobs, DC, Bowman, JD, Barry, N, Beardsley, AP, Bernardi, G, Briggs, F, Cappallo, RJ, Carroll, P, Deshpande, AA, de Oliveira-Costa, A, Dillon, JS, Ewall-Wice, A, Feng, L, Greenhill, LJ, Hazelton, BJ, Hernquist, L, Hewitt, JN, Hurley-Walker, N, Johnston-Hollitt, M, Kaplan, DL, Kim, H-S, Kittiwisit, P, Lenc, E, Line, J, Loeb, A, Lonsdale, CJ, McKinley, B, McWhirter, SR, Mitchell, DA, Morales, MF, Morgan, E, Neben, AR, Oberoi, D, Offringa, AR, Ord, SM, Paul, S, Pindor, B, Pober, JC, Prabu, T, Procopio, P, Riding, J, Shankar, NU, Sethi, SK, Srivani, KS, Subrahmanyan, R, Sullivan, IS, Tegmark, M, Tingay, SJ, Trott, CM, Wayth, RB, Webster, RL, Williams, A, Williams, CL, and Wyithe, JSB

Abstract

We confirm our recent prediction of the "pitchfork" foreground signature in power spectra of high-redshift 21 cm measurements where the interferometer is sensitive to large-scale structure on all baselines. This is due to the inherent response of a wide-field instrument and is characterized by enhanced power from foreground emission in Fourier modes adjacent to those considered to be the most sensitive to the cosmological H I signal. In our recent paper, many signatures from the simulation that predicted this feature were validated against Murchison Widefield Array (MWA) data, but this key pitchfork signature was close to the noise level. In this paper, we improve the data sensitivity through the coherent averaging of 12 independent snapshots with identical instrument settings and provide the first confirmation of the prediction with a signal-to-noise ratio > 10. This wide-field effect can be mitigated by careful antenna designs that suppress sensitivity near the horizon. Simple models for antenna apertures that have been proposed for future instruments such as the Hydrogen Epoch of Reionization Array and the Square Kilometre Array indicate they should suppress foreground leakage from the pitchfork by ~40 dB relative to the MWA and significantly increase the likelihood of cosmological signal detection in these critical Fourier modes in the three-dimensional power spectrum.

Published
2015

26. HERA Phase I Limits on the Cosmic 21 cm Signal: Constraints on Astrophysics and Cosmology during the Epoch of Reionization

Author

The HERA Collaboration, Abdurashidova, Zara, Aguirre, James E., Alexander, Paul, Ali, Zaki, Balfour, Yanga, Barkana, Rennan, Beardsley, Adam, Bernardi, Gianni, Billings, Tashalee, Bowman, Judd, Bradley, Richard, Bull, Phillip, Burba, Jacob, Carey, Steven, Carilli, Christopher, Cheng, Carina, DeBoer, David, Dexter, Matthew, Acedo, Eloy de Lera, Dillon, Joshua, Ely, John, Ewall-Wice, Aaron, Fagnoni, Nicolas, Fialkov, Anastasia, Fritz, Randall, Furlanetto, Steven, Gale-Sides, Kingsley, Glendenning, Brian, Gorthi, Deepthi, Greig, Bradley, Grobbelaar, Jasper, Halday, Ziyaad, Hazelton, Bryna, Heimersheim, Stefan, Hewitt, Jacqueline, Hickish, Jack, Jacobs, Daniel, Julius, Austin, Kern, Nicholas, Kerrigan, Joshua, Kittiwisit, Piyanat, Kohn, Saul, Kolopanis, Matthew, Lanman, Adam, La Plante, Paul, Lekalake, Telalo, Lewis, David, Liu, Adrian, Ma, Yin-Zhe, MacMahon, David, Malan, Lourence, Malgas, Cresshim, Maree, Matthys, Martinot, Zachary, Matsetela, Eunice, Mesinger, Andrei, Mirocha, Jordan, Molewa, Mathakane, Morales, Miguel, Mosiane, Tshegofalang, Munoz, Julian, Murray, Steven, Neben, Abraham, Nikolic, Bojan, Nunhokee, Chuneeta Devi, Parsons, Aaron, Patra, Nipanjana, Pieterse, Samantha, Pober, Jonathan, Qin, Yuxiang, Razavi-Ghods, N., Reis, Itamar, Ringuette, Jon, Robnett, James, Rosie, Kathryn, Santos, Mario, Sikder, Sudipta, Sims, Peter, Smith, Craig, Syce, Angelo, Thyagarajan, Nithyanandan, Williams, Peter, Zheng, Haoxuan, Abdurashidova, Z., Aguirre, J. E., Alexander, P., Ali, Z. S., Balfour, Y., Barkana, R., Beardsley, A. P., 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., Dillon, J. S., Ely, J., Ewall-Wice, A., Fagnoni, N., Fialkov, A., Fritz, R., Furlanetto, S. R., Gale-Sides, K., Glendenning, B., Gorthi, D., Greig, B., Grobbelaar, J., Halday, Z., Hazelton, B. J., Heimersheim, S., Hewitt, J. N., Hickish, J., Jacobs, D. C., Julius, A., Kern, N. S., Kerrigan, J., Kittiwisit, P., Kohn, S. A., Kolopanis, M., Lanman, A., La Plante, P., Lekalake, T., Lewis, D., Liu, A., Ma, Y. -Z., Macmahon, D., Malan, L., Malgas, C., Maree, M., Martinot, Z. E., Matsetela, E., Mesinger, A., Mirocha, J., Molewa, M., Morales, M. F., Mosiane, T., Munoz, J. B., Murray, S. G., Neben, A. R., Nikolic, B., Nunhokee, C. D., Parsons, A. R., Patra, N., Pieterse, S., Pober, J. C., Qin, Y., Razavi-Ghods, N., Reis, I., Ringuette, J., Robnett, J., Rosie, K., Santos, M. G., Sikder, S., Sims, P., Smith, C., Syce, A., Thyagarajan, N., Williams, P. K. G., Zheng, H., USA, GBR, ZAF, Aguirre, JE [0000-0002-4810-666X], Barkana, R [0000-0002-1557-693X], Beardsley, AP [0000-0001-9428-8233], Bernardi, G [0000-0002-0916-7443], Bowman, JD [0000-0002-8475-2036], Bradley, RF [0000-0003-1172-8331], Bull, P [0000-0001-5668-3101], Carilli, CL [0000-0001-6647-3861], Deboer, DR [0000-0003-3197-2294], Dillon, JS [0000-0003-3336-9958], Ewall-Wice, A [0000-0002-0086-7363], Fialkov, A [0000-0002-1369-633X], Furlanetto, SR [0000-0002-0658-1243], Gorthi, D [0000-0002-0829-167X], Greig, B [0000-0002-4085-2094], Hazelton, BJ [0000-0001-7532-645X], Heimersheim, S [0000-0001-9631-4212], Hewitt, JN [0000-0002-4117-570X], Jacobs, DC [0000-0002-0917-2269], Kern, NS [0000-0002-8211-1892], Kerrigan, J [0000-0002-1876-272X], Kittiwisit, P [0000-0003-0953-313X], Kohn, SA [0000-0001-6744-5328], Kolopanis, M [0000-0002-2950-2974], La Plante, P [0000-0002-4693-0102], Liu, A [0000-0001-6876-0928], Ma, YZ [0000-0001-8108-0986], Mesinger, A [0000-0003-3374-1772], Mirocha, J [0000-0002-8802-5581], Morales, MF [0000-0001-7694-4030], Munoz, JB [0000-0002-8984-0465], Neben, AR [0000-0001-7776-7240], Nunhokee, CD [0000-0002-5445-6586], Patra, N [0000-0002-9457-1941], Pober, JC [0000-0002-3492-0433], Qin, Y [0000-0002-4314-1810], Reis, I [0000-0002-6203-7496], Santos, MG [0000-0003-3892-3073], Sims, P [0000-0002-2871-0413], Thyagarajan, N [0000-0003-1602-7868], and Apollo - University of Cambridge Repository

Subjects
High Energy Physics - Theory, Cosmology and Nongalactic Astrophysics (astro-ph.CO), 010308 nuclear & particles physics, astro-ph.GA, hep-th, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, High Energy Physics - Theory (hep-th), Settore FIS/05 - Astronomia e Astrofisica, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, astro-ph.CO, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Recently, the Hydrogen Epoch of Reionization Array (HERA) collaboration has produced the experiment's first upper limits on the power spectrum of 21-cm fluctuations at z~8 and 10. Here, we use several independent theoretical models to infer constraints on the intergalactic medium (IGM) and galaxies during the epoch of reionization (EoR) from these limits. We find that the IGM must have been heated above the adiabatic cooling threshold by z~8, independent of uncertainties about the IGM ionization state and the nature of the radio background. Combining HERA limits with galaxy and EoR observations constrains the spin temperature of the z~8 neutral IGM to 27 K < T_S < 630 K (2.3 K < T_S < 640 K) at 68% (95%) confidence. They therefore also place a lower bound on X-ray heating, a previously unconstrained aspects of early galaxies. For example, if the CMB dominates the z~8 radio background, the new HERA limits imply that the first galaxies produced X-rays more efficiently than local ones (with soft band X-ray luminosities per star formation rate constrained to L_X/SFR = { 10^40.2, 10^41.9 } erg/s/(M_sun/yr) at 68% confidence), consistent with expectations of X-ray binaries in low-metallicity environments. The z~10 limits require even earlier heating if dark-matter interactions (e.g., through millicharges) cool down the hydrogen gas. Using a model in which an extra radio background is produced by galaxies, we rule out (at 95% confidence) the combination of high radio and low X-ray luminosities of L_{r,ν}/SFR > 3.9 x 10^24 W/Hz/(M_sun/yr) and L_X/SFR, 40 pages, 19 figures, accepted to ApJ

Published
2022

27. First Results from HERA Phase I: Upper Limits on the Epoch of Reionization 21 cm Power Spectrum

Author

The HERA Collaboration, Abdurashidova, Zara, Aguirre, James E., Alexander, Paul, Ali, Zaki S., Balfour, Yanga, Beardsley, Adam P., Bernardi, Gianni, Billings, Tashalee S., Bowman, Judd D., Bradley, Richard F., Bull, Philip, Burba, Jacob, Carey, Steve, Carilli, Chris L., Cheng, Carina, DeBoer, David R., Dexter, Matt, Acedo, Eloy de Lera, Dibblee-Barkman, Taylor, Dillon, Joshua S., Ely, John, Ewall-Wice, Aaron, Fagnoni, Nicolas, Fritz, Randall, Furlanetto, Steven R., Gale-Sides, Kingsley, Glendenning, Brian, Gorthi, Deepthi, Greig, Bradley, Grobbelaar, Jasper, Halday, Ziyaad, Hazelton, Bryna J., Hewitt, Jacqueline N., Hickish, Jack, Jacobs, Daniel C., Julius, Austin, Kern, Nicholas S., Kerrigan, Joshua, Kittiwisit, Piyanat, Kohn, Saul A., Kolopanis, Matthew, Lanman, Adam, La Plante, Paul, Lekalake, Telalo, Lewis, David, Liu, Adrian, MacMahon, David, Malan, Lourence, Malgas, Cresshim, Maree, Matthys, Martinot, Zachary E., Matsetela, Eunice, Mesinger, Andrei, Molewa, Mathakane, Morales, Miguel F., Mosiane, Tshegofalang, Murray, Steven G., Neben, Abraham R., Nikolic, Bojan, Nunhokee, Chuneeta D., Parsons, Aaron R., Patra, Nipanjana, Pascua, Robert, Pieterse, Samantha, Pober, Jonathan C., Razavi-Ghods, Nima, Ringuette, Jon, Robnett, James, Rosie, Kathryn, Sims, Peter, Singh, Saurabh, Smith, Craig, Syce, Angelo, Thyagarajan, Nithyanandan, Williams, Peter K. G., Zheng, Haoxuan, USA, GBR, ZAF, 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., Carey, S., Carilli, C. L., Cheng, C., Deboer, D. R., Dexter, M., De Lera Acedo, E., Dibblee-Barkman, T., 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., Kern, N. S., 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., Mesinger, A., Molewa, M., Morales, M. F., Mosiane, T., Murray, S. G., Neben, A. R., Nikolic, B., Nunhokee, C. D., Parsons, A. R., Patra, N., Pascua, R., Pieterse, S., Pober, J. C., Razavi-Ghods, N., Ringuette, J., Robnett, J., Rosie, K., Sims, P., Singh, S., Smith, C., Syce, A., Thyagarajan, N., Williams, P. K. G., Zheng, H., Aguirre, JE [0000-0002-4810-666X], Beardsley, AP [0000-0001-9428-8233], Bernardi, G [0000-0002-0916-7443], Bowman, JD [0000-0002-8475-2036], Bull, P [0000-0001-5668-3101], Carilli, CL [0000-0001-6647-3861], Deboer, DR [0000-0003-3197-2294], Dillon, JS [0000-0003-3336-9958], Ewall-Wice, A [0000-0002-0086-7363], Furlanetto, SR [0000-0002-0658-1243], Gorthi, D [0000-0002-0829-167X], Greig, B [0000-0002-4085-2094], Hazelton, BJ [0000-0001-7532-645X], Jacobs, DC [0000-0002-0917-2269], Kern, NS [0000-0002-8211-1892], Kerrigan, J [0000-0002-1876-272X], Kittiwisit, P [0000-0003-0953-313X], Kohn, SA [0000-0001-6744-5328], Kolopanis, M [0000-0002-2950-2974], Liu, A [0000-0001-6876-0928], Mesinger, A [0000-0003-3374-1772], Morales, MF [0000-0001-7694-4030], Murray, SG [0000-0003-3059-3823], Neben, AR [0000-0001-7776-7240], Nunhokee, CD [0000-0002-5445-6586], Patra, N [0000-0002-9457-1941], Pober, JC [0000-0002-3492-0433], Sims, P [0000-0002-2871-0413], Singh, S [0000-0001-7755-902X], Thyagarajan, N [0000-0003-1602-7868], Williams, PKG [0000-0003-3734-3587], and Apollo - University of Cambridge Repository

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), Settore FIS/05 - Astronomia e Astrofisica, Space and Planetary Science, astro-ph.GA, Astrophysics of Galaxies (astro-ph.GA), astro-ph.CO, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We report upper-limits on the Epoch of Reionization (EoR) 21 cm power spectrum at redshifts 7.9 and 10.4 with 18 nights of data ($\sim36$ hours of integration) from Phase I of the Hydrogen Epoch of Reionization Array (HERA). The Phase I data show evidence for systematics that can be largely suppressed with systematic models down to a dynamic range of $\sim10^9$ with respect to the peak foreground power. This yields a 95% confidence upper limit on the 21 cm power spectrum of $\Delta^2_{21} \le (30.76)^2\ {\rm mK}^2$ at $k=0.192\ h\ {\rm Mpc}^{-1}$ at $z=7.9$, and also $\Delta^2_{21} \le (95.74)^2\ {\rm mK}^2$ at $k=0.256\ h\ {\rm Mpc}^{-1}$ at $z=10.4$. At $z=7.9$, these limits are the most sensitive to-date by over an order of magnitude. While we find evidence for residual systematics at low line-of-sight Fourier $k_\parallel$ modes, at high $k_\parallel$ modes we find our data to be largely consistent with thermal noise, an indicator that the system could benefit from deeper integrations. The observed systematics could be due to radio frequency interference, cable sub-reflections, or residual instrumental cross-coupling, and warrant further study. This analysis emphasizes algorithms that have minimal inherent signal loss, although we do perform a careful accounting in a companion paper of the small forms of loss or bias associated with the pipeline. Overall, these results are a promising first step in the development of a tuned, instrument-specific analysis pipeline for HERA, particularly as Phase II construction is completed en route to reaching the full sensitivity of the experiment., Comment: Accepted to ApJ. https://reionization.org/science/public-data-release-1/

Published
2021

28. Imaging and Modeling Data from the Hydrogen Epoch of Reionization Array

Author

Juan Mena Parra, Piyanat Kittiwisit, Kingsley Gale-Sides, Joshua Kerrigan, Honggeun Kim, Adrian Liu, Phil Bull, Nipanjana Patra, Ziyaad Halday, Matthys Maree, James E. Aguirre, Bryna J. Hazelton, Jacqueline N. Hewitt, Zara Abdurashidova, Saul A. Kohn, Judd D. Bowman, Matt Dexter, K. Gale-Sides, Samantha Pieterse, Paul La Plante, Mathakane Molewa, James Kent, Nithyanandan Thyagarajan, Eunice Matsetela, Nicolas Fagnoni, Adam P. Beardsley, Alec Josaitis, Kathryn Rosie, David MacMahon, Jonathan C. Pober, Andrei Mesinger, Jasper Grobbelaar, Tashalee S. Billings, Zachary E. Martinot, Tshegofalang Mosiane, Abraham R. Neben, Austin Julius, Randall Fritz, Siyanda Matika, Brian Glendenning, Carina Cheng, Peter Sims, Paul Alexander, Daniel C. Jacobs, Steve R. Furlanetto, Gianni Bernardi, Bradley Greig, Lourence Malan, Nima Razavi-Ghods, Cresshim Malgas, Yanga Balfour, Nicholas S. Kern, Telalo Lekalake, David DeBoer, Aaron R. Parsons, Richard F. Bradley, Matthew Kolopanis, Deepthi Gorthi, Peter K. G. Williams, James Robnett, Joshua S. Dillon, Chris Carilli, Eloy de Lera Acedo, Miguel F. Morales, Zaki S. Ali, Bojan Nikolic, Aaron Ewall-Wice, Jack Hickish, Jacob Burba, Angelo Syce, Haoxuan Zheng, Adam Lanman, ITA, USA, ZAF, Carilli, C. L., Thyagarajan, N., Kent, J., Nikolic, B., Gale-Sides, K., Kern, N. S., Bernardi, G., Mesinger, A., Matika, S., Abdurashidova, Zara, Aguirre, James E., Paul, Alexander Christian, Ali, Zaki S., Balfour, Yanga, Beardsley, Adam P., Billings, Tashalee S., Bowman, Judd D., Bradley, Richard F., Bull, Phil, Burba, Jacob, Cheng, Carina, Deboer, David R., Dexter, Matt, Acedo, Eloy de Lera, Dillon, Joshua S., Ewall-Wice, Aaron, Fagnoni, Nicola, Fritz, Randall, Furlanetto, Steve R., Gale-Sides, Kingsley, Glendenning, Brian, Gorthi, Deepthi, Greig, Bradley, Grobbelaar, Jasper, Halday, Ziyaad, Hazelton, Bryna J., Hewitt, Jacqueline N., Hickish, Jack, Jacobs, Daniel C., Josaitis, Alec, Julius, Austin, Kerrigan, Joshua, Kim, Honggeun, Kittiwisit, Piyanat, Kohn, Saul A., Kolopanis, Matthew, Lanman, Adam, Plante, Paul La, Lekalake, Telalo, Liu, Adrian, Macmahon, David, Malan, Lourence, Malgas, Cresshim, Maree, Matthy, Martinot, Zachary E., Matsetela, Eunice, Molewa, Mathakane, Morales, Miguel F., Mosiane, Tshegofalang, Neben, Abraham R., Parra, Juan Mena, Parsons, Aaron R., Patra, Nipanjana, Pieterse, Samantha, Pober, Jonathan C., Razavi-Ghods, Nima, Robnett, Jame, Rosie, Kathryn, Sims, Peter, Syce, Angelo, Williams, Peter K. G., Zheng, Haoxuan, Carilli, CL [0000-0001-6647-3861], Thyagarajan, N [0000-0003-1602-7868], Kern, NS [0000-0002-8211-1892], Bernardi, G [0000-0002-0916-7443], Aguirre, JE [0000-0002-4810-666X], Beardsley, AP [0000-0001-9428-8233], Bowman, JD [0000-0002-8475-2036], Bull, P [0000-0001-5668-3101], 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], Kerrigan, J [0000-0002-1876-272X], Kittiwisit, P [0000-0003-0953-313X], Kohn, SA [0000-0001-6744-5328], Kolopanis, M [0000-0002-2950-2974], Liu, A [0000-0001-6876-0928], Morales, MF [0000-0001-7694-4030], Neben, AR [0000-0001-7776-7240], Patra, N [0000-0002-9457-1941], Pober, JC [0000-0002-3492-0433], Williams, PKG [0000-0003-3734-3587], and Apollo - University of Cambridge Repository

Subjects
Physics, Cosmological evolution, Hydrogen, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, chemistry.chemical_element, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Cosmology, Data modeling, chemistry, Reionization, Space and Planetary Science, 0103 physical sciences, Radio interferometry, Astrophysics - Instrumentation and Methods for Astrophysics, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

We analyze data from the Hydrogen Epoch of Reionization Array. This is the third in a series of papers on the closure phase delay-spectrum technique designed to detect the HI 21cm 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 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 $\sim 80$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 $\sim 10$ 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 implications due to this missing structure in the models, including calibration, and in the search for the HI 21cm signal, as well as possible mitigation techniques., Comment: 17 pages, 10 figures, accepted for the ApJ Supplement

Published
2020

29. Validation of the HERA Phase I Epoch of Reionization 21 cm Power Spectrum Software Pipeline

Author

Aguirre, James E., Murray, Steven G., Pascua, Robert, Martinot, Zachary E., Burba, Jacob, Dillon, Joshua S., Jacobs, Daniel C., Kern, Nicholas S., Kittiwisit, Piyanat, Kolopanis, Matthew, Lanman, Adam, Liu, Adrian, Whitler, Lily, Abdurashidova, Zara, Alexander, Paul, Ali, Zaki S., Balfour, Yanga, Beardsley, Adam P., BERNARDI, GIANNI, Billings, Tashalee S., Bowman, Judd D., Bradley, Richard F., BULL, PHILIP, Carey, Steve, Carilli, Chris L., Cheng, Carina, DeBoer, David R., Dexter, Matt, de Lera Acedo, Eloy, Ely, John, Ewall-Wice, Aaron, Fagnoni, Nicolas, Fritz, Randall, Furlanetto, Steven R., Gale-Sides, Kingsley, Glendenning, Brian, Gorthi, Deepthi, Greig, Bradley, Grobbelaar, Jasper, Halday, Ziyaad, Hazelton, Bryna J., Hewitt, Jacqueline N., Hickish, Jack, Julius, Austin, Kerrigan, Joshua, Kohn, Saul A., La Plante, Paul, Lekalake, Telalo, Lewis, David, MacMahon, David, Malan, Lourence, Malgas, Cresshim, Maree, Matthys, Matsetela, Eunice, Mesinger, Andrei, Molewa, Mathakane, Morales, Miguel F., Mosiane, Tshegofalang, Neben, Abraham R., Nikolic, Bojan, Parsons, Aaron R., Patra, Nipanjana, Pieterse, Samantha, Pober, Jonathan C., Razavi-Ghods, Nima, Ringuette, Jon, Robnett, James, Rosie, Kathryn, Santos, Mario G., Sims, Peter, Singh, Saurabh, Smith, Craig, Syce, Angelo, Thyagarajan, Nithyanandan, Williams, Peter K. G., Zheng, Haoxuan, HERA Collaboration, Aguirre, J. E., Murray, S. G., Pascua, R., Martinot, Z. E., Burba, J., Dillon, J. S., Jacobs, D. C., Kern, N. S., Kittiwisit, P., Kolopanis, M., Lanman, A., Liu, A., Whitler, L., Abdurashidova, Z., Alexander, P., Ali, Z. S., Balfour, Y., Beardsley, A. P., Bernardi, G., Billings, T. S., Bowman, J. D., Bradley, R. F., Bull, P., 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., Julius, A., Kerrigan, J., Kohn, S. A., La Plante, P., Lekalake, T., Lewis, D., Macmahon, D., Malan, L., Malgas, C., Maree, M., Matsetela, E., 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., Ringuette, J., Robnett, J., Rosie, K., Santos, M. G., Sims, P., Singh, S., Smith, C., Syce, A., Thyagarajan, N., Williams, P. K. G., Zheng, H., USA, GBR, ZAF, Aguirre, JE [0000-0002-4810-666X], Murray, SG [0000-0003-3059-3823], Dillon, JS [0000-0003-3336-9958], Jacobs, DC [0000-0002-0917-2269], Kern, NS [0000-0002-8211-1892], Kittiwisit, P [0000-0003-0953-313X], Kolopanis, M [0000-0002-2950-2974], Lanman, A [0000-0003-2116-3573], Liu, A [0000-0001-6876-0928], Beardsley, AP [0000-0001-9428-8233], Bernardi, G [0000-0002-0916-7443], Bowman, JD [0000-0002-8475-2036], Bradley, RF [0000-0003-1172-8331], Bull, P [0000-0001-5668-3101], Carilli, CL [0000-0001-6647-3861], Deboer, DR [0000-0003-3197-2294], Ewall-Wice, A [0000-0002-0086-7363], Furlanetto, SR [0000-0002-0658-1243], Gorthi, D [0000-0002-0829-167X], Greig, B [0000-0002-4085-2094], Hazelton, BJ [0000-0001-7532-645X], Hewitt, JN [0000-0002-4117-570X], Kerrigan, J [0000-0002-1876-272X], Kohn, SA [0000-0001-6744-5328], Mesinger, A [0000-0003-3374-1772], Morales, MF [0000-0001-7694-4030], Neben, AR [0000-0001-7776-7240], Patra, N [0000-0002-9457-1941], Pober, JC [0000-0002-3492-0433], Santos, MG [0000-0003-3892-3073], Sims, P [0000-0002-2871-0413], Singh, S [0000-0001-7755-902X], and Apollo - University of Cambridge Repository

Subjects
Settore FIS/05 - Astronomia e Astrofisica, 010308 nuclear & particles physics, Space and Planetary Science, 0103 physical sciences, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, 01 natural sciences, astro-ph.IM
Abstract

We describe the validation of the HERA Phase I software pipeline by a series of modular tests, building up to an end-to-end simulation. The philosophy of this approach is to validate the software and algorithms used in the Phase I upper limit analysis on wholly synthetic data satisfying the assumptions of that analysis, not addressing whether the actual data meet these assumptions. We discuss the organization of this validation approach, the specific modular tests performed, and the construction of the end-to-end simulations. We explicitly discuss the limitations in scope of the current simulation effort. With mock visibility data generated from a known analytic power spectrum and a wide range of realistic instrumental effects and foregrounds, we demonstrate that the current pipeline produces power spectrum estimates that are consistent with known analytic inputs to within thermal noise levels (at the 2 sigma level) for k > 0.2 h/Mpc for both bands and fields considered. Our input spectrum is intentionally amplified to enable a strong `detection' at k ~0.2 h/Mpc -- at the level of ~25 sigma -- with foregrounds dominating on larger scales, and thermal noise dominating at smaller scales. Our pipeline is able to detect this amplified input signal after suppressing foregrounds with a dynamic range (foreground to noise ratio) of > 10^7. Our validation test suite uncovered several sources of scale-independent signal loss throughout the pipeline, whose amplitude is well-characterized and accounted for in the final estimates. We conclude with a discussion of the steps required for the next round of data analysis., 32 pages, 20 figures. Submitted to the Astrophysical Journal

Published
2022

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