G. Bernardi
A5017361196- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Antenna Design and Optimization
- Radio Wave Propagation Studies
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Superconducting and THz Device Technology
- Cosmology and Gravitation Theories
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Astronomical Observations and Instrumentation
- Electromagnetic Compatibility and Measurements
- Particle Accelerators and Free-Electron Lasers
- Soil Moisture and Remote Sensing
- GNSS positioning and interference
- Stellar, planetary, and galactic studies
- Scientific Research and Discoveries
- Astrophysics and Star Formation Studies
- Dark Matter and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Millimeter-Wave Propagation and Modeling
- Geophysics and Sensor Technology
South African Radio Astronomy Observatory
2019-2025
Rhodes University
2016-2025
Istituto di Radioastronomia di Bologna
2017-2025
University of California, Berkeley
2023
SKA Telescope, South Africa
2013-2022
National Institute for Astrophysics
2006-2022
Center for Astrophysics Harvard & Smithsonian
2010-2021
Arcetri Astrophysical Observatory
2021
University of Bologna
2003-2018
The University of Sydney
2015
LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in north of Netherlands and across europe. Utilizing novel phased-array design, LOFAR covers largely unexplored low-frequency range from 10-240 MHz provides number unique observing capabilities. Spreading out core located near village Exloo northeast Netherlands, total 40 stations are nearing completion. A further five have been deployed throughout Germany, one station has built each France, Sweden, UK....
The Murchison Widefield Array (MWA) is one of three Square Kilometre Precursor telescopes and located at the Radio-astronomy Observatory in Shire mid-west Western Australia, a location chosen for its extremely low levels radio frequency interference. MWA operates frequencies, 80-300 MHz, with processed bandwidth 30.72 MHz both linear polarisations, consists 128 aperture arrays (known as tiles) distributed over ~3 km diameter area. Novel hybrid hardware/software correlation real-time imaging...
Astronomical wide-field imaging of interferometric radio data is computationally expensive, especially for the large volumes created by modern non-coplanar many-element arrays. We present a new imager that uses w-stacking algorithm and can make use w-snapshot algorithm. The performance dependences casa's w-projection our are analysed analytical functions derived describe required computing cost both imagers. On from Murchison Widefield Array, we find method to be an order magnitude faster...
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,...
We describe and compare several post-correlation radio frequency interference (RFI) classification methods. As data sizes of observations grow with new improved telescopes, the need for completely automated, robust methods RFI mitigation is pressing. investigated find that, sets we used, most accurate among them SumThreshold method. This a method formed from combination existing techniques, including way thresholding. iterative estimates astronomical signal by carrying out surface fit in...
Abstract Significant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in southern hemisphere designed specifically to explore low-frequency astronomical sky between 80 300 MHz with arcminute angular resolution high survey efficiency. will enable advances along four key science themes, including searching redshifted 21-cm emission from EoR early Universe; Galactic extragalactic all-sky surveys;...
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...
The Murchison Widefield Array (MWA) has collected hundreds of hours Epoch Reionization (EoR) data and now faces the challenge overcoming foreground systematic contamination to reduce a cosmological measurement. We introduce several novel analysis techniques such as cable reflection calibration, hyper-resolution gridding kernels, diffuse model subtraction, quality control methods. Each change pipeline is tested against two dimensional power spectrum figure merit demonstrate improvement....
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...
Future high redshift 21-cm experiments will suffer from a degree of contamination, due both to astrophysical foregrounds and non-astrophysical instrumental effects. In order reliably extract the cosmological signal observed data, it is essential understand very well all data components their influence on extracted signal. Here we present simulated datacubes discuss possible statistical effects data. The foreground maps are produced assuming 5 deg x windows that match those expected be by...
We present techniques for bridging the gap between idealized inverse covariance weighted quadratic estimation of 21 cm power spectra and real-world challenges presented universally by interferometric observation. By carefully evaluating various estimators adapting our large but incomplete data sets, we develop a robust spectrum framework that preserves so-called "Epoch Reionization (EoR) window" keeps track estimator errors covariances. apply method to observations from 32-tile prototype...
<i>Context. <i/>The cosmological 21 cm line promises to be a formidable tool for cosmology, allowing the investigation of end so-called dark ages, when first galaxies formed.<i>Aims. <i/>Astrophysical foregrounds are expected about three orders magnitude greater than signal and therefore represent serious contamination line. Detailed knowledge both their intensity polarization structure on relevant angular scale 1–30 arcmin will essential extracting from data.<i>Methods. <i/>We present...
We describe a new low-frequency wideband radio survey of the southern sky. Observations covering 72-231MHz and Declinations south +30° have been performed with Murchison Widefield Array "extended" Phase I configuration over 2018-2020 will be processed to form data products including continuum polarisation images mosaics, multi-frequency catalogues, transient search data, ionospheric measurements. From pilot field described in this work, we publish an initial release 1,447 deg2 4 h≤ RA≤ 13 h,...
The first station of the Long Wavelength Array (LWA1) was completed in April 2011 and is currently performing observations resulting from its call for proposals addition to a continuing program commissioning characterization observations. instrument consists 258 dual-polarization dipoles, which are digitized combined into beams. Four independently-steerable beams available, each with two tunings 16 MHz bandwidth that can be independently tuned any frequency between 10 88 MHz. system...
The Large-aperture Experiment to Detect the Dark Age (LEDA) was designed detect predicted O(100) mK sky-averaged absorption of cosmic microwave background by hydrogen in neutral pre- and intergalactic medium just after cosmological Age. spectral signature would be associated with emergence a diffuse Lyα from starlight during 'Cosmic Dawn'. Recently, Bowman et al. have reported detection this feature, an unexpectedly large amplitude 530 mK, centred at 78 MHz. Verification result independent...
In this paper we explore for the first time relative magnitudes of three fundamental sources uncertainty, namely, foreground contamination, thermal noise and sample variance in detecting HI power spectrum from Epoch Reionization (EoR). We derive limits on sensitivity a Fourier synthesis telescope to detect EoR based its array configuration statistical representation images made by instrument. use Murchison Widefield Array (MWA) our studies. Using unified framework estimating signal...
HI intensity mapping (IM) is a novel technique capable of the large-scale structure Universe in three dimensions and delivering exquisite constraints on cosmology, by using as biased tracer dark matter density field.This achieved measuring redshifted 21cm line over sky range redshifts without requirement to resolve individual galaxies.In this chapter, we investigate potential SKA1 deliver maps broad frequencies substantial fraction sky.By pinning down baryon acoustic oscillation redshift...
The Murchison Widefield Array (MWA) is a new low-frequency interferometric radio telescope built in Western Australia at one of the locations future Square Kilometre (SKA). We describe automated radio-frequency interference (RFI) detection strategy implemented for MWA, which based on AOFlagger platform, and present 72-231-MHz RFI statistics from 10 observing nights. removes 1.1% data. digital TV (DTV) observed 3% time due to occasional ionospheric or atmospheric propagation. After excision,...