Eloy de Lera Acedo
A5001024440- Radio Astronomy Observations and Technology
- Antenna Design and Optimization
- Astrophysics and Cosmic Phenomena
- Antenna Design and Analysis
- Electromagnetic Compatibility and Measurements
- Radio Wave Propagation Studies
- Superconducting and THz Device Technology
- Microwave Engineering and Waveguides
- Advanced Antenna and Metasurface Technologies
- Millimeter-Wave Propagation and Modeling
- Electromagnetic Scattering and Analysis
- Soil Moisture and Remote Sensing
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Electromagnetic Compatibility and Noise Suppression
- Advanced Optical Sensing Technologies
- Advanced Wireless Communication Techniques
- Precipitation Measurement and Analysis
- Cosmology and Gravitation Theories
- Power Line Communications and Noise
- Astronomical Observations and Instrumentation
- Scientific Research and Discoveries
- Particle Accelerators and Free-Electron Lasers
- Satellite Image Processing and Photogrammetry
- Gyrotron and Vacuum Electronics Research
University of Cambridge
2016-2025
Institute for Advanced Study
2023
University of California, Santa Cruz
2023
Tel Aviv University
2023
University of the Western Cape
2023
Queen Mary University of London
2021
Cavendish Hospital
2019
Universidad Carlos III de Madrid
2017
UCLouvain
2017
Netherlands Institute for Radio Astronomy
2009
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,...
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 report characterization results for an engineering prototype of a next-generation low-frequency radio astronomy array. This prototype, which we refer to as the Aperture Array Verification System 0.5 (AAVS0.5), is sparse pseudo-random array 16 log-periodic antennas designed 70-450 MHz. It co-located with Murchison Widefield (MWA) at Radioastronomy Observatory (MRO) near Australian Square Kilometre (SKA) core site. characterize AAVS0.5 using two methods: in-situ interferometry astronomical...
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...
The HI 21cm absorption line is masked by bright foregrounds and systematic distortions that arise due to the chromaticity of antenna used make observation coupling spectral inhomogeneity these foregrounds. We demonstrate are sufficient conceal signal when not perfectly achromatic simple corrections assuming a constant spatial distribution foreground power insufficient overcome them. then propose new physics-motivated method modelling experiments in order fit chromatic as part This done...
ABSTRACT Maximally Smooth Functions (MSFs) are a form of constrained functions in which there no inflection points or zero crossings high-order derivatives. Consequently, they have applications to signal recovery experiments where signals interest expected be non-smooth features masked by larger smooth foregrounds. They can also act as powerful tool for diagnosing the presence systematics. The nature MSFs makes fitting these non-trivial task. We introduce maxsmooth, an open-source package...
ABSTRACT Global 21-cm cosmology aims to investigate the cosmic dawn and epoch of reionization by measuring sky averaged H i absorption signal, which requires, accurate modelling of, or correction for, bright radio foregrounds distortions arising from chromaticity antenna beam. We effect improving foreground fitting data sets many observation times simultaneously in a single Bayesian analysis, for same parameter set performing these fits on simulated data. find that hexagonal dipole antenna,...
Abstract The redshifted 21 cm line of cosmic atomic hydrogen is one the most auspicious tools in deciphering early Universe. Recovering this signal remains an ongoing problem for cosmologists field, with being hidden behind foregrounds approximately five orders magnitude brighter than itself. A traditional forward modelling data analysis pipeline using Bayesian and a physically motivated foreground model to find shows great promise case unchanging environmental conditions. However we...
A fast full-wave simulation technique is presented for the analysis of large irregular planar arrays identical 3-D metallic antennas. The solution method relies on Macro Basis Functions (MBF) approach and an interpolatory to compute interactions between MBFs. Harmonic-polynomial (HARP) model established near-field in a modified system coordinates. For extremely made complex antennas, two approaches assuming limited radius influence mutual coupling are considered: one based sparse-matrix LU...
The Radio Experiment for the Analysis of Cosmic Hydrogen (REACH) is a new instrument dedicated to detection red-shifted radio signature signal from times when universe transitioned vast empty space realm celestial objects. These are known as Dawn and Epoch Re-ionization. REACH will use our best knowledge Physics that governed Universe during these early epochs much brighter foreground signals later added faint cosmic signal. Furthermore, it make physics rooted models describing...
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...
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....
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 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 modelled the two major layer of Earth's ionosphere, F-layer and D-layer, by a simplified spatial model with temporal variance to study chromatic ionospheric effects on global 21-cm observations. From analyses, we found that magnitude disruptions due refraction absorption can be greater than expected signal, variation its differ, depending conditions. Within parameter space adopted in model, shape signal is distorted after propagating through while amplitude weakened. It observed do not...
Emulation of the Global (sky-averaged) 21-cm signal with neural networks has been shown to be an essential tool for physical modelling. In this paper we present globalemu, a emulator that uses redshift as character defining variable alongside set astrophysical parameters estimate brightness temperature. Combined physically-motivated data pre-processing makes reliable and fast is relatively insensitive network design. globalemu can emulate high resolution in 1.3 ms comparison 133 ms, factor...
Properties of the first generation stars (Pop III), such as their initial mass function (IMF), are poorly constrained by observations and have yet to converge between simulations. The cosmological 21-cm signal neutral hydrogen is predicted be sensitive Lyman-band photons produced these stars, thus providing a unique way probe stellar population. In this paper, we investigate impacts Pop III IMF on cosmic dawn via Wouthuysen-Field effect, Lyman-Werner feedback, Ly-alpha heating, CMB heating....
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...
ABSTRACT The early Universe, spanning 400 000 to million years after the big bang (z ≈ 1100–11), has been left largely unexplored as light from luminous objects is too faint be observed directly. While new experiments are pushing redshift limit of direct observations, measurements in low-frequency radio band promise probe star and black hole formation via observations hydrogen 21-cm line. In this work, we explore synergies between data HERA SARAS 3 unresolved X-ray backgrounds using...