A5036630991- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Superconducting and THz Device Technology
- Antenna Design and Optimization
- Radio Wave Propagation Studies
- Soil Moisture and Remote Sensing
- Galaxies: Formation, Evolution, Phenomena
- Precipitation Measurement and Analysis
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Cosmology and Gravitation Theories
- Scientific Research and Discoveries
- Advanced Wireless Communication Techniques
- Electromagnetic Compatibility and Measurements
- Magnesium Alloys: Properties and Applications
- Planetary Science and Exploration
- Water Quality Monitoring and Analysis
- Astro and Planetary Science
- History and Developments in Astronomy
- Gamma-ray bursts and supernovae
- Orthopaedic implants and arthroplasty
- Spacecraft Design and Technology
- Aerospace Engineering and Energy Systems
- Advanced Thermodynamic Systems and Engines
- Metamaterials and Metasurfaces Applications
California Institute of Technology
2022-2025
Arizona State University
2018-2023
M S Ramaiah University of Applied Sciences
2020
Raman Research Institute
2014-2016
Abstract We present new constraints on parameters of cosmic dawn and the epoch reionization derived from EDGES High-Band spectrum (90–190 MHz). The are probed by evaluating global 21 cm signals generated with recently developed Global21cm tool. This tool uses neural networks trained tested ∼30,000 spectra produced semi-numerical simulations that assume standard thermal evolution microwave background intergalactic medium. From our analysis, we constrain at 68% (1) minimum virial circular...
Abstract We use the sky-average spectrum measured by EDGES High-band (90–190 MHz) to constrain parameters of early galaxies independent absorption feature at 78 MHz reported Bowman et al. These represent traditional models cosmic dawn and epoch reionization produced with 21cmFAST simulation code. The considered are (1) UV ionizing efficiency ( ζ ); (2) minimum halo virial temperature hosting efficient star-forming <?CDATA ${T}_{\mathrm{vir}}^{\min }$?> (3) integrated soft-band X-ray...
We report the spectral index of diffuse radio emission between 50 and 100 MHz from data collected with two implementations Experiment to Detect Global EoR Signature (EDGES) low-band system. EDGES employs a wide beam zenith-pointing dipole antenna centred on declination $-26.7^\circ$. measure sky brightness temperature as function frequency averaged over 244 nights acquired 14 September 2016 27 August 2017. derive index, $\beta$, local sidereal time (LST) using night-time two-parameter...
ABSTRACT Accurately accounting for spectral structure in spectrometer data induced by instrumental chromaticity on scales relevant detection of the 21-cm signal is among most significant challenges global analysis. In publicly available Experiment to Detect Global Epoch Reionization Signature low-band set, this complicating suppressed using beam-factor-based correction (BFCC), which works dividing a sky-map-weighted model instrument beam. Several analyses these have employed models that...
Comparing composite models for multi-component observational data is a prevalent scientific challenge. When fitting models, there exists the potential systematics from poor fit of one model component to be absorbed by another, resulting in providing an accurate aggregate but yielding biased posteriori estimates individual components. We begin defining classification scheme comparison scenarios, identifying two categories: category I, where with and predictive components are separable through...
Abstract The response of the antenna is a source uncertainty in measurements with Experiment to Detect Global Epoch Reionization Signature (EDGES). We aim validate electromagnetic beam model low-band (50–100 MHz) dipole comparisons between models and against data. find that simulations simplified over an infinite perfectly conducting ground plane are, one exception, robust changes numerical solver code or algorithm. For actual finite realistic soil properties, we two out three solvers agree...
FarView is an early-stage concept for a large, low-frequency radio observatory, manufactured in-situ on the lunar far side using metals extracted from regolith. It consists of 100,000 dipole antennas in compact subarrays distributed over large area but with empty space between core-halo structure. covers total ∼200 km2, has dense core within inner 36 and ∼power-law falloff antenna density out to ∼14 km center. With this design, it relatively easy identify multiple viable build sites side....
Abstract Line-intensity mapping is a promising probe of the Universe’s large-scale structure. We explore sensitivity DSA-2000, forthcoming array consisting over 2000 dishes, to statistical power spectrum neutral hydrogen’s 21 cm emission line. These measurements would reveal distribution hydrogen throughout near-redshift Universe without necessitating resolving individual sources. The success these relies on instrument’s and resilience systematics. show that DSA-2000 will have needed detect...
Abstract One key challenge in detecting a 21 cm cosmological signal at z > 6 is to separate the from foreground emission. This can be studied power spectrum space where confined low delay (or, equivalently, k ∥ ) modes, whereas spread out high modes. When there calibration error, however, chromaticity of gain errors propagates estimate and contaminates modes for detection. The Hydrogen Epoch Reionization Array (HERA) employs high-precision scheme using redundancy measurements. In this...
We develop a Bayesian model that jointly constrains receiver calibration, foregrounds and cosmic 21cm signal for the EDGES global 21\,cm experiment. This simultaneously describes calibration data taken in lab along with sky-data low-band antenna. apply our to same (both sky calibration) used report evidence first star formation 2018. find does not contribute significant uncertainty inferred (<1%), though joint is able more robustly estimate foreground models are otherwise too inflexible...
Abstract Detecting cosmological signals from the Epoch of Reionization (EoR) requires high-precision calibration to isolate foreground emission. In radio interferometry, perturbed primary beams antenna elements can disrupt precise calibration, which results in contamination foreground-free region, or EoR window, cylindrically averaged power spectrum. For Hydrogen Array (HERA), we simulate and characterize that are induced by feed motions, such as axial, lateral, tilting above 14 m dish. To...
The critical component of radio astronomy radiometers built to detect redshifted 21-cm signals from Cosmic Dawn is the antenna element. We describe design and performance an octave bandwidth cone disc this signal in band 40 90 MHz. predicted be a wideband spectral feature orders magnitude weaker than sky ground brightness. Thus, engineering challenge at low frequencies that able provide with high fidelity faint cosmological signal, along foreground sky, receiver. characteristics must not...
Abstract Accurate detection of the cosmological 21 cm global signal requires galactic foreground models that can remove power over 10 6 . Although and unavoidably exhibit overlap in their vector spaces inducing bias error extracted signal, a second source arises from inadequate models, i.e., cannot fit spectra down to noise level signal. We therefore test which seven commonly employed models—including nonlinear linear forward polynomials, maximally smooth polynomials—fit realistic simulated...
We present the design, construction, and measurements of electromagnetic performance a wideband space beam splitter. The splitter is sheet in free that designed to divide incident radiation into reflected transmitted components for interferometer measurement spectral features mean cosmic radio background. Analysis two-element configuration with vertical between pair antennas leads requirement be resistive resistance η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML"...
Scattering from objects near an antenna produce correlated signals strong compact radio sources in a manner similar to those used by the Sea Interferometer measure source positions using fine frequency structure total power spectrum of single antenna. These fringes or ripples due signal interference are present at low level any and major systematics systems global redshifted 21-cm early universe. In on cliff above sea is add direct path reflected thereby forming interferometer. This was for...
We use EDGES measurements to determine scale and zero-level corrections the diffuse radio surveys by Guzm\'an et al. at $45$ MHz Landecker & Wielebinski $150$ MHz. find that map requires a correction of $1.076 \pm 0.034$ ($2\sigma$) $-160 78$ K best-fit data. For map, is $1.112 0.023$ $0.7 6.0$ ($2\sigma$). The uncertainties are dominated systematic effects, which most significant uncertainty in calibration receivers, antenna pointing, tropospheric ionospheric effects. propagate estimate...
Precision calibration poses challenges to experiments probing the redshifted 21-cm signal of neutral hydrogen from Cosmic Dawn and Epoch Reionization (z~30-6). In both interferometric global experiments, systematic is leading source error. Though many aspects have been studied, overlap between two types instruments has received less attention. We investigate sky based total power measurements with a HERA dish an EDGES style antenna understand role auto-correlations in interferometer...
FarView is an early-stage concept for a large, low-frequency radio observatory, manufactured in-situ on the lunar far side using metals extracted from regolith. It consists of 100,000 dipole antennas in compact subarrays distributed over large area but with empty space between core-halo structure. covers total ~200 km2, has dense core within inner ~36 and ~power-law falloff antenna density out to ~14 km center. With this design, it relatively easy identify multiple viable build sites side....
We present the design, construction and measurements of electromagnetic performance a wideband space beam splitter. The splitter is designed to power divide incident radiation into reflected transmitted components for interferometer measurement spectral features in mean cosmic radio background. Analysis 2-element configuration with vertical between pair antennas leads requirement that be resistive sheet resistance {\eta}o /2, where impedance free space. transmission reflection properties...
Accurate detection of the cosmological 21-cm global signal requires galactic foreground models which can remove power over ~$10^6$. Although and unavoidably exhibit overlap in their vector-spaces inducing bias error extracted signal, a second source arises from inadequate models, i.e. cannot fit spectra down to noise level signal. We therefore test seven commonly employed -- including nonlinear linear forward-models, polynomials, maximally-smooth polynomials realistic simulated mock spectra,...
Abstract Diffuse radio recombination lines (RRLs) in the Galaxy are possible foregrounds for redshifted 21 cm experiments. We use EDGES drift scans centered at −26.°7 decl. to characterize diffuse RRLs across southern sky. find that averaged over large antenna beam (72° × 110°) reach minimum amplitudes of R.A. = 2–6 hr. In this region, C α absorption amplitude is 33 ± 11 mK (1 σ ) 50–87 MHz (27 ≳ z 15 line) and increases strongly as frequency decreases. β H consistent with no detection 13 14...