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1. The MeerKAT Galaxy Cluster Legacy Survey I. Survey Overview and Highlights

Author

Knowles, K., Cotton, W. D., Rudnick, L., Camilo, F., Goedhart, S., Deane, R., Ramatsoku, M., Bietenholz, M. F., Brüggen, M., Button, C., Chen, H., Chibueze, J. O., Clarke, T. E., de Gasperin, F., Ianjamasimanana, R., Józsa, G. I. G., Hilton, M., Kesebonye, K. C., Kolokythas, K., Kraan-Korteweg, R. C., Lawrie, G., Lochner, M., Loubser, S. I., Marchegiani, P., Mhlahlo, N., Moodley, K., Murphy, E., Namumba, B., Oozeer, N., Parekh, V., Pillay, D. S., Passmoor, S. S., Ramaila, A. J. T., Ranchod, S., Retana-Montenegro, E., Sebokolodi, L., Sikhosana, S. P., Smirnov, O., Thorat, K., Venturi, T., Abbott, T. D., Adam, R. M., Adams, G., Aldera, M. A., Bauermeister, E. F., Bennett, T. G. H., Bode, W. A., Botha, D. H., Botha, A. G., Brederode, L. R. S., Buchner, S., Burger, J. P., Cheetham, T., de Villiers, D. I. L., Dikgale-Mahlakoana, M. A., Toit, L. J. du, Esterhuyse, S. W. P., Fadana, G., Fanaroff, B. L., Fataar, S., Foley, A. R., Fourie, D. J., Frank, B. S., Gamatham, R. R. G., Gatsi, T. G., Geyer, M., Gouws, M., Gumede, S. C., Heywood, I., Hlakola, M. J., Hokwana, A., Hoosen, S. W., Horn, D. M., Horrell, J. M. G., Hugo, B. V., Isaacson, A. R., Jonas, J. L., Jordaan, J. D. B., Joubert, A. F., Julie, R. P. M., Kapp, F. B., Kasper, V. A., Kenyon, J. S., Kotzé, P. P. A., Kotze, A. G., Kriek, N., Kriel, H., Krishnan, V. K., Kusel, T. W., Legodi, L. S., Lehmensiek, R., Liebenberg, D., Lord, R. T., Lunsky, B. M., Madisa, K., Magnus, L. G., Main, J. P. L., Makhaba, A., Makhathini, S., Malan, J. A., Manley, J. R., Marais, S. J., Maree, M. D. J., Martens, A., Mauch, T., McAlpine, K., Merry, B. C., Millenaar, R. P., Mokone, O. J., Monama, T. E., Mphego, M. C., New, W. S., Ngcebetsha, B., Ngoasheng, K. J., Ockards, M. T., Otto, A. J., Patel, A. A., Peens-Hough, A., Perkins, S. J., Ramanujam, N. M., Ramudzuli, Z. R., Ratcliffe, S. M., Renil, R., Robyntjies, A., Rust, A. N., Salie, S., Sambu, N., Schollar, C. T. G., Schwardt, L. C., Schwartz, R. L., Serylak, M., Siebrits, R., Sirothia, S. K., Slabber, M., Sofeya, L., Taljaard, B., Tasse, C., Tiplady, A. J., Toruvanda, O., Twum, S. N., van Balla, T. J., van der Byl, A., van der Merwe, C., van Dyk, C. L., Van Tonder, V., Van Wyk, R., Venter, A. J., Venter, M., Welz, M. G., Williams, L. P., and Xaia, B.

Subjects
Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

MeerKAT's large number of antennas, spanning 8 km with a densely packed 1 km core, create a powerful instrument for wide-area surveys, with high sensitivity over a wide range of angular scales. The MeerKAT Galaxy Cluster Legacy Survey (MGCLS) is a programme of long-track MeerKAT L-band (900-1670 MHz) observations of 115 galaxy clusters, observed for $\sim$6-10 hours each in full polarisation. The first legacy product data release (DR1), made available with this paper, includes the MeerKAT visibilities, basic image cubes at $\sim$8" resolution, and enhanced spectral and polarisation image cubes at $\sim$8" and 15" resolutions. Typical sensitivities for the full-resolution MGCLS image products are $\sim$3-5 {\mu}Jy/beam. The basic cubes are full-field and span 4 deg^2. The enhanced products consist of the inner 1.44 deg^2 field of view, corrected for the primary beam. The survey is fully sensitive to structures up to $\sim$10' scales and the wide bandwidth allows spectral and Faraday rotation mapping. HI mapping at 209 kHz resolution can be done at $0

Published
2021
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2. The 1.28 GHz MeerKAT DEEP2 Image

Author

Mauch, T., Cotton, W. D., Condon, J. J., Matthews, A. M., Abbott, T. D., Adam, R. M., Aldera, M. A., Asad, K. M. B., Bauermeister, E. F., Bennett, T. G. H., Bester, H., Botha, D. H., Brederode, L. R. S., Brits, Z. B., Buchner, S. J., Burger, J. P., Camilo, F., Chalmers, J. M., Cheetham, T., de Villiers, D., de Villiers, M. S., Dikgale-Mahlakoana, M. A., Toit, L. J. du, Esterhuyse, S. W. P., Fadana, G., Fanaroff, B. L., Fataar, S., February, S., Frank, B. S., Gamatham, R. R. G., Geyer, M., Goedhart, S., Gounden, S., Gumede, S. C., Heywood, I., Hlakola, M. J., Horrell, J. M. G., Hugo, B., Isaacson, A. R., Józsa, G. I. G., Jonas, J. L., Julie, R. P. M., Kapp, F. B., Kasper, V. A., Kenyon, J. S., Kotzé, P. P. A., Kriek, N., Kriel, H., Kusel, T. W., Lehmensiek, R., Loots, A., Lord, R. T., Lunsky, B. M., Madisa, K., Magnus, L. G., Main, J. P. L., Malan, J. A., Manley, J. R., Marais, S. J., Martens, A., Merry, B., Millenaar, R., Mnyandu, N., Moeng, I. P. T., Mokone, O. J., Monama, T. E., Mphego, M. C., New, W. S., Ngcebetsha, B., Ngoasheng, K. J., Ockards, M. T. O., Oozeer, N., Otto, A. J., Patel, A. A., Peens-Hough, A., Perkins, S. J., Ramaila, A. J. T., Ramudzuli, Z. R., Renil, R., Richter, L. L., Robyntjies, A., Salie, S., Schollar, C. T. G., Schwardt, L. C., Serylak, M., Siebrits, R., Sirothia, S. K., Smirnov, O. M., Sofeya, L., Stone, G., Taljaard, B., Tasse, C., Theron, I. P., Tiplady, A. J., Toruvanda, O., Twum, S. N., van Balla, T. J., van der Byl, A., van der Merwe, C., Van Tonder, V., Wallace, B. H., Welz, M. G., Williams, L. P., and Xaia, B.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We present the confusion-limited 1.28 GHz MeerKAT DEEP2 image covering one $\approx 68'$ FWHM primary beam area with $7.6''$ FWHM resolution and $0.55 \pm 0.01$ $\mu$Jy/beam rms noise. Its J2000 center position $\alpha=04^h 13^m 26.4^s$, $\delta=-80^\circ 00' 00''$ was selected to minimize artifacts caused by bright sources. We introduce the new 64-element MeerKAT array and describe commissioning observations to measure the primary beam attenuation pattern, estimate telescope pointing errors, and pinpoint $(u,v)$ coordinate errors caused by offsets in frequency or time. We constructed a 1.4 GHz differential source count by combining a power-law count fit to the DEEP2 confusion $P(D)$ distribution from $0.25$ to $10$ $\mu$Jy with counts of individual DEEP2 sources between $10$ $\mu$Jy and $2.5$ mJy. Most sources fainter than $S \sim 100$ $\mu$Jy are distant star-forming galaxies obeying the FIR/radio correlation, and sources stronger than $0.25$ $\mu$Jy account for $\sim93\%$ of the radio background produced by star-forming galaxies. For the first time, the DEEP2 source count has reached the depth needed to reveal the majority of the star formation history of the universe. A pure luminosity evolution of the 1.4 GHz local luminosity function consistent with the Madau & Dickinson (2014) model for the evolution of star-forming galaxies based on UV and infrared data underpredicts our 1.4 GHz source count in the range $-5 \lesssim \log[S(\mathrm{Jy})] \lesssim -4$., Comment: 20 pages, 18 figures. Accepted for publication in ApJ

Published
2019
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3. Foreground modelling via Gaussian process regression: An application to HERA data

Author

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

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

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

Published
2020

4. 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

5. 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

6. The MeerKAT Galaxy Cluster Legacy Survey

Author

Knowles, K., primary, Cotton, W. D., additional, Rudnick, L., additional, Camilo, F., additional, Goedhart, S., additional, Deane, R., additional, Ramatsoku, M., additional, Bietenholz, M. F., additional, Brüggen, M., additional, Button, C., additional, Chen, H., additional, Chibueze, J. O., additional, Clarke, T. E., additional, de Gasperin, F., additional, Ianjamasimanana, R., additional, Józsa, G. I. G., additional, Hilton, M., additional, Kesebonye, K. C., additional, Kolokythas, K., additional, Kraan-Korteweg, R. C., additional, Lawrie, G., additional, Lochner, M., additional, Loubser, S. I., additional, Marchegiani, P., additional, Mhlahlo, N., additional, Moodley, K., additional, Murphy, E., additional, Namumba, B., additional, Oozeer, N., additional, Parekh, V., additional, Pillay, D. S., additional, Passmoor, S. S., additional, Ramaila, A. J. T., additional, Ranchod, S., additional, Retana-Montenegro, E., additional, Sebokolodi, L., additional, Sikhosana, S. P., additional, Smirnov, O., additional, Thorat, K., additional, Venturi, T., additional, Abbott, T. D., additional, Adam, R. M., additional, Adams, G., additional, Aldera, M. A., additional, Bauermeister, E. F., additional, Bennett, T. G. H., additional, Bode, W. A., additional, Botha, D. H., additional, Botha, A. G., additional, Brederode, L. R. S., additional, Buchner, S., additional, Burger, J. P., additional, Cheetham, T., additional, de Villiers, D. I. L., additional, Dikgale-Mahlakoana, M. A., additional, du Toit, L. J., additional, Esterhuyse, S. W. P., additional, Fadana, G., additional, Fanaroff, B. L., additional, Fataar, S., additional, Foley, A. R., additional, Fourie, D. J., additional, Frank, B. S., additional, Gamatham, R. R. G., additional, Gatsi, T. G., additional, Geyer, M., additional, Gouws, M., additional, Gumede, S. C., additional, Heywood, I., additional, Hlakola, M. J., additional, Hokwana, A., additional, Hoosen, S. W., additional, Horn, D. M., additional, Horrell, J. M. G., additional, Hugo, B. V., additional, Isaacson, A. R., additional, Jonas, J. L., additional, Jordaan, J. D. B., additional, Joubert, A. F., additional, Julie, R. P. M., additional, Kapp, F. B., additional, Kasper, V. A., additional, Kenyon, J. S., additional, Kotzé, P. P. A., additional, Kotze, A. G., additional, Kriek, N., additional, Kriel, H., additional, Krishnan, V. K., additional, Kusel, T. W., additional, Legodi, L. S., additional, Lehmensiek, R., additional, Liebenberg, D., additional, Lord, R. T., additional, Lunsky, B. M., additional, Madisa, K., additional, Magnus, L. G., additional, Main, J. P. L., additional, Makhaba, A., additional, Makhathini, S., additional, Malan, J. A., additional, Manley, J. R., additional, Marais, S. J., additional, Maree, M. D. J., additional, Martens, A., additional, Mauch, T., additional, McAlpine, K., additional, Merry, B. C., additional, Millenaar, R. P., additional, Mokone, O. J., additional, Monama, T. E., additional, Mphego, M. C., additional, New, W. S., additional, Ngcebetsha, B., additional, Ngoasheng, K. J., additional, Ockards, M. T., additional, Otto, A. J., additional, Patel, A. A., additional, Peens-Hough, A., additional, Perkins, S. J., additional, Ramanujam, N. M., additional, Ramudzuli, Z. R., additional, Ratcliffe, S. M., additional, Renil, R., additional, Robyntjies, A., additional, Rust, A. N., additional, Salie, S., additional, Sambu, N., additional, Schollar, C. T. G., additional, Schwardt, L. C., additional, Schwartz, R. L., additional, Serylak, M., additional, Siebrits, R., additional, Sirothia, S. K., additional, Slabber, M., additional, Sofeya, L., additional, Taljaard, B., additional, Tasse, C., additional, Tiplady, A. J., additional, Toruvanda, O., additional, Twum, S. N., additional, van Balla, T. J., additional, van der Byl, A., additional, van der Merwe, C., additional, van Dyk, C. L., additional, Van Tonder, V., additional, Van Wyk, R., additional, Venter, A. J., additional, Venter, M., additional, Welz, M. G., additional, Williams, L. P., additional, and Xaia, B., additional

Published
2022
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7. 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

8. The 1.28 GHz MeerKAT DEEP2 Image

Author

Mauch, T., primary, Cotton, W. D., additional, Condon, J. J., additional, Matthews, A. M., additional, Abbott, T. D., additional, Adam, R. M., additional, Aldera, M. A., additional, Asad, K. M. B., additional, Bauermeister, E. F., additional, Bennett, T. G. H., additional, Bester, H., additional, Botha, D. H., additional, Brederode, L. R. S., additional, Brits, Z. B., additional, Buchner, S. J., additional, Burger, J. P., additional, Camilo, F., additional, Chalmers, J. M., additional, Cheetham, T., additional, Villiers, D. de, additional, Villiers, M. S. de, additional, Dikgale-Mahlakoana, M. A., additional, Toit, L. J. du, additional, Esterhuyse, S. W. P., additional, Fadana, G., additional, Fanaroff, B. L., additional, Fataar, S., additional, February, S., additional, Frank, B. S., additional, Gamatham, R. R. G., additional, Geyer, M., additional, Goedhart, S., additional, Gounden, S., additional, Gumede, S. C., additional, Heywood, I., additional, Hlakola, M. J., additional, Horrell, J. M. G., additional, Hugo, B., additional, Isaacson, A. R., additional, Józsa, G. I. G., additional, Jonas, J. L., additional, Julie, R. P. M., additional, Kapp, F. B., additional, Kasper, V. A., additional, Kenyon, J. S., additional, Kotzé, P. P. A., additional, Kriek, N., additional, Kriel, H., additional, Kusel, T. W., additional, Lehmensiek, R., additional, Loots, A., additional, Lord, R. T., additional, Lunsky, B. M., additional, Madisa, K., additional, Magnus, L. G., additional, Main, J. P. L., additional, Malan, J. A., additional, Manley, J. R., additional, Marais, S. J., additional, Martens, A., additional, Merry, B., additional, Millenaar, R., additional, Mnyandu, N., additional, Moeng, I. P. T., additional, Mokone, O. J., additional, Monama, T. E., additional, Mphego, M. C., additional, New, W. S., additional, Ngcebetsha, B., additional, Ngoasheng, K. J., additional, Ockards, M. T. O., additional, Oozeer, N., additional, Otto, A. J., additional, Patel, A. A., additional, Peens-Hough, A., additional, Perkins, S. J., additional, Ramaila, A. J. T., additional, Ramudzuli, Z. R., additional, Renil, R., additional, Richter, L. L., additional, Robyntjies, A., additional, Salie, S., additional, Schollar, C. T. G., additional, Schwardt, L. C., additional, Serylak, M., additional, Siebrits, R., additional, Sirothia, S. K., additional, Smirnov, O. M., additional, Sofeya, L., additional, Stone, G., additional, Taljaard, B., additional, Tasse, C., additional, Theron, I. P., additional, Tiplady, A. J., additional, Toruvanda, O., additional, Twum, S. N., additional, Balla, T. J. van, additional, Byl, A. van der, additional, Merwe, C. van der, additional, Tonder, V. Van, additional, Wallace, B. H., additional, Welz, M. G., additional, Williams, L. P., additional, and Xaia, B., additional

Published
2020
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9. 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

10. Foreground modelling via Gaussian process regression: an application to HERA data

Author

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

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

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

Published
2020

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

Author

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

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

Foreground power dominates the measurements of interferometers that seek a statistical detection of highly-redshifted HI emission from the Epoch of Reionization (EoR). The chromaticity of the instrument creates a boundary in the Fourier transform of frequency (proportional to $k_\parallel$) between spectrally smooth emission, characteristic of the strong synchrotron foreground (the "wedge"), and the spectrally structured emission from HI in the EoR (the "EoR window"). Faraday rotation can inject spectral structure into otherwise smooth polarized foreground emission, which through instrument effects or miscalibration could possibly pollute the EoR window. Using data from the HERA 19-element commissioning array, we investigate the polarization response of this new instrument in the power spectrum domain. We perform a simple image-based calibration based on the unpolarized diffuse emission of the Global Sky Model, and show that it achieves qualitative redundancy between the nominally-redundant baselines of the array and reasonable amplitude accuracy. We construct power spectra of all fully polarized coherencies in all pseudo-Stokes parameters. We compare to simulations based on an unpolarized diffuse sky model and detailed electromagnetic simulations of the dish and feed, confirming that in Stokes I, the calibration does not add significant spectral structure beyond the expected level. Further, this calibration is stable over the 8 days of observations considered. Excess power is seen in the power spectra of the linear polarization Stokes parameters which is not easily attributable to leakage via the primary beam, and results from some combination of residual calibration errors and actual polarized emission. Stokes V is found to be highly discrepant from the expectation of zero power, strongly pointing to the need for more accurate polarized calibration., Comment: 21 pages, 12 figures, submitted to ApJ

Published
2018
Full Text
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