Jasper Grobbelaar
A5067642637- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Radio Wave Propagation Studies
- Antenna Design and Optimization
- Electromagnetic Compatibility and Measurements
- Galaxies: Formation, Evolution, Phenomena
- Soil Moisture and Remote Sensing
- Particle Accelerators and Free-Electron Lasers
- Millimeter-Wave Propagation and Modeling
- Superconducting and THz Device Technology
- Diamond and Carbon-based Materials Research
- Pulsed Power Technology Applications
- Gyrotron and Vacuum Electronics Research
- Advanced Wireless Communication Techniques
- Luminescence Properties of Advanced Materials
- Astronomical Observations and Instrumentation
- Optical measurement and interference techniques
- Telecommunications and Broadcasting Technologies
- Molecular Biology Techniques and Applications
- Adaptive optics and wavefront sensing
- Radio Frequency Integrated Circuit Design
- Ethics in Clinical Research
- Forensic and Genetic Research
- Scientific Research and Discoveries
- Photonic and Optical Devices
South African Radio Astronomy Observatory
2020-2025
University of Cape Town
2024
University of California, Berkeley
2023
SKA Telescope, South Africa
2015-2022
Brown University
2021
De Beers (South Africa)
1990-1991
Rhodes University
1967
The Hydrogen Epoch of Reionization Array (HERA) is a staged experiment to measure 21 cm emission from the primordial intergalactic medium (IGM) throughout cosmic reionization ($z=6-12$), and explore earlier epochs our Cosmic Dawn ($z\sim30$). During these epochs, early stars black holes heated ionized IGM, introducing fluctuations in emission. HERA designed characterize evolution power spectrum constrain timing morphology reionization, properties first galaxies, large-scale structure,...
In this paper, we report new limits on 21cm emission from cosmic reionization based a 135-day observing campaign with 64-element deployment of the Donald C. Backer Precision Array for Probing Epoch Reionization (PAPER) in South Africa. This work extends presented Parsons et al. (2014) more collecting area, longer period, improved redundancy-based calibration, optimal fringe-rate filtering, and power-spectral analysis using quadratic estimators. The result is $2\sigma$ upper limit...
Abstract We report upper limits on the Epoch of Reionization 21 cm power spectrum at redshifts 7.9 and 10.4 with 18 nights data (∼36 hr integration) from Phase I Hydrogen Array (HERA). The show evidence for systematics that can be largely suppressed systematic models down to a dynamic range ∼10 9 respect peak foreground power. This yields 95% confidence limit <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi...
Abstract Recently, the Hydrogen Epoch of Reionization Array (HERA) has produced experiment’s first upper limits on power spectrum 21 cm fluctuations at z ∼ 8 and 10. Here, we use several independent theoretical models to infer constraints intergalactic medium (IGM) galaxies during epoch reionization from these limits. We find that IGM must have been heated above adiabatic-cooling threshold by 8, uncertainties about ionization radio background. Combining HERA with complementary observations...
Abstract We report the most sensitive upper limits to date on 21 cm epoch of reionization power spectrum using 94 nights observing with Phase I Hydrogen Epoch Reionization Array (HERA). Using similar analysis techniques as in previously reported limits, we find at 95% confidence that Δ 2 ( k = 0.34 h Mpc −1 ) ≤ 457 mK z 7.9 and 0.36 3496 10.4, an improvement by a factor 2.1 2.6, respectively. These are mostly consistent thermal noise over wide range after our data quality cuts, despite...
Abstract This paper presents the design and deployment of Hydrogen Epoch Reionization Array (HERA) phase II system. HERA is designed as a staged experiment targeting 21 cm emission measurements Reionization. First results from I array are published early 2022, system nearing completion. We describe discuss progress on commissioning future upgrades. As designated Square Kilometre pathfinder instrument, we also show number “case studies” that investigate systematics seen while system, which...
We present constraints on both the kinetic temperature of intergalactic medium (IGM) at z=8.4, and models for heating IGM high-redshift with X-ray emission from first collapsed objects. These are derived using a semi-analytic method to explore new measurements 21 cm power spectrum Donald C. Backer Precision Array Probing Epoch Reionization (PAPER), which were presented in companion paper, Ali et al. (2015). Twenty-one spectra amplitudes hundreds mK^2 can be generically produced if is...
We present a study of internal reflection and cross coupling systematics in Phase I the Hydrogen Epoch Reionization Array (HERA). In companion paper, we outlined mathematical formalism for such presented algorithms modeling removing them from data. this work, apply these techniques to data HERA's first observing season as method demonstration. The show evidence that, without removal, would hinder detection 21 cm power spectrum targeted EoR line-of-sight modes range 0.2 < k_parallel 0.5\ h^-1...
ABSTRACT In 21-cm cosmology, precision calibration is key to the separation of neutral hydrogen signal from very bright but spectrally smooth astrophysical foregrounds. The Hydrogen Epoch Reionization Array (HERA), an interferometer specialized for cosmology and now under construction in South Africa, was designed be largely calibrated using self-consistency repeated measurements same interferometric modes. This technique, known as redundant-baseline resolves most internal degrees freedom...
Radio Frequency Interference (RFI) is an ever-present limiting factor among radio telescopes even in the most remote observing locations. When looking to retain maximum amount of sensitivity and reduce contamination for Epoch Reionization studies, identification removal RFI especially important. In addition improved identification, we must also take into account computational efficiency RFI-Identification algorithm as interferometer arrays such Hydrogen Array grow larger number receivers. To...
Abstract We discuss absolute calibration strategies for Phase I of the Hydrogen Epoch Reionization Array (HERA), which aims to measure cosmological 21 cm signal from Reionization. HERA is a drift-scan array with 10° wide field view, meaning bright, well-characterized point-source transits are scarce. This, combined HERA’s redundant sampling uv plane and modest angular resolution instrument, make traditional sky-based self-calibration techniques difficult implement high dynamic range....
ABSTRACT The detection of the Epoch Reionization (EoR) delay power spectrum using a ‘foreground avoidance method’ highly depends on instrument chromaticity. systematic effects induced by radio telescope spread foreground signal in domain, which contaminates EoR window theoretically observable. Applied to Hydrogen Array (HERA), this paper combines detailed electromagnetic and electrical simulations order model chromatic instrument, quantify its frequency time responses. In particular,...
We describe the validation of HERA Phase I software pipeline by a series modular tests, building up to an end-to-end simulation. The philosophy this approach is validate and algorithms used in upper limit analysis on wholly synthetic data satisfying assumptions that analysis, not addressing whether actual meet these assumptions. discuss organization approach, specific tests performed, construction simulations. explicitly limitations scope current simulation effort. With mock visibility...
The construction of the seven-dish Karoo Array Telescope (KAT-7) array in region Northern Cape South Africa was intended primarily as an engineering prototype for technologies and techniques applicable to MeerKAT telescope. This paper looks at main scientific highlights from this effort, discusses their applicability both other next-generation radio telescopes. In particular, we found that composite dish surface works well, but it becomes complicated fabricate a lacking circular symmetry;...
The key challenge in the observation of redshifted 21-cm signal from cosmic reionization is its separation much brighter foreground emission. Such relies on different spectral properties two components, although, real life, intrinsic spectrum often corrupted by instrumental response, inducing systematic effects that can further jeopardize measurement signal. In this paper, we use Gaussian Process Regression to model both emission and systematics $\sim 2$ hours data Hydrogen Epoch...
ABSTRACT Detection of the faint 21 cm line emission from Cosmic Dawn and Epoch Reionization will require not only exquisite control over instrumental calibration systematics to achieve necessary dynamic range observations but also validation analysis techniques demonstrate their statistical properties signal loss characteristics. A key ingredient in achieving this is ability perform high-fidelity simulations kinds data that are produced by large, many-element, radio interferometric arrays...
Characterizing the epoch of reionization (EoR) at z≳6 via redshifted 21 cm line neutral Hydrogen (H i) is critical to modern astrophysics and cosmology, thus a key science goal many current planned low-frequency radio telescopes. The primary challenge detecting this signal overwhelmingly bright foreground emission these frequencies, placing stringent requirements on knowledge instruments inaccuracies in analyses. Results from experiments have largely been limited not by thermal sensitivity...
Radio Frequency Interference (RFI) is one of the systematic challenges preventing 21cm interferometric instruments from detecting Epoch Reionization. To mitigate effects RFI on data analysis pipelines, numerous inpaint techniques have been developed to restore corrupted data. We examine qualitative and quantitative errors introduced into visibilities power spectrum due inpainting. perform our simulated as well real Hydrogen Reionization Array (HERA) Phase 1 upper limits. also introduce a...
Foreground power dominates the measurements of interferometers that seek a statistical detection highly-redshifted HI emission from Epoch Reionization (EoR). The chromaticity instrument creates boundary in Fourier transform frequency (proportional to $k_\parallel$) between spectrally smooth emission, characteristic strong synchrotron foreground (the "wedge"), and structured EoR "EoR window"). Faraday rotation can inject spectral structure into otherwise polarized which through effects or...
Combining the visibilities measured by an interferometer to form a cosmological power spectrum is complicated process. In delay-based analysis, mapping between instrumental and space not one-to-one relation. Instead, neighbouring modes contribute at one point, with their respective contributions encoded in window functions. To better understand interferometer, we assess impact of instrument characteristics analysis choices on these Focusing Hydrogen Epoch Reionization Array (HERA) as case...
Precise measurements of the 21 cm power spectrum are crucial for understanding physical processes hydrogen reionization. Currently, this probe is being pursued by low-frequency radio interferometer arrays. As these experiments come closer to making a first detection signal, error estimation will play an increasingly important role in setting robust measurements. Using delay approach, we have produced critical examination different ways that one can estimate bars on spectrum. We do through...
As current- and next-generation astronomical instruments come online, they will generate an unprecedented deluge of data. Analyzing these data in real time presents unique conceptual computational challenges, their long-term storage archiving is scientifically essential for generating reliable, reproducible results. We present here the real-time processing (RTP) system Hydrogen Epoch Reionization Array (HERA), a radio interferometer endeavoring to provide first detection highly redshifted 21...