Nipanjana Patra
A5038107587- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Antenna Design and Optimization
- Radio Wave Propagation Studies
- Superconducting and THz Device Technology
- Electromagnetic Compatibility and Measurements
- Galaxies: Formation, Evolution, Phenomena
- Heusler alloys: electronic and magnetic properties
- Magnetic and transport properties of perovskites and related materials
- Particle Accelerators and Free-Electron Lasers
- Soil Moisture and Remote Sensing
- ZnO doping and properties
- Luminescence Properties of Advanced Materials
- MXene and MAX Phase Materials
- Multiferroics and related materials
- Copper-based nanomaterials and applications
- Ferroelectric and Piezoelectric Materials
- Particle accelerators and beam dynamics
- Millimeter-Wave Propagation and Modeling
- Gyrotron and Vacuum Electronics Research
- Catalytic Processes in Materials Science
- Optical measurement and interference techniques
- Pulsed Power Technology Applications
- Microwave Dielectric Ceramics Synthesis
- Advanced Wireless Communication Techniques
University of California, Berkeley
2015-2024
Raman Research Institute
2011-2023
Massachusetts Institute of Technology
2023
International Centre for Radio Astronomy Research
2020-2023
Curtin University
2020-2023
Indian Institute of Technology Indore
2023
Arizona State University
2021
National Radio Astronomy Observatory
2020
Bhabha Atomic Research Centre
2016-2019
Homi Bhabha National Institute
2018-2019
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...
ABSTRACT Unaccounted for systematics from foregrounds and instruments can severely limit the sensitivity of current experiments detecting redshifted 21 cm signals Epoch Reionization (EoR). Upcoming are faced with a challenge to deliver more collecting area per antenna element without degrading data systematics. This paper its companions show that dishes viable achieving this balance using Hydrogen Array (HERA) as an example. Here, we specifically identify spectral associated power pattern...
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...
SARAS is a correlation spectrometer connected to frequency independent antenna that purpose-designed for precision measurements of the radio background at long wavelengths. The design, calibration and observing strategies admit solutions internal additive contributions radiometer response, hence separation these contaminants from temperature. We present here wideband measurement sky spectrum by provides an accurate absolute brightness spectral index between 110 175 MHz. Accuracy in limited...
The Hydrogen Epoch of Reionization Array (HERA) is a radio interferometer aiming to detect the power spectrum 21 cm fluctuations from neutral hydrogen (EOR). Drawing on lessons Murchison Widefield (MWA) and Precision for Probing (PAPER), HERA hexagonal array large (14 m diameter) dishes with suspended dipole feeds. Not only does dish determine overall sensitivity, it affects observed frequency structure foregrounds in interferometer. This first series four papers characterizing angular...
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 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 We use time-domain electromagnetic simulations to determine the spectral characteristics of Hydrogen Epoch Reionization Arrays (HERA) antenna. These are part a multi-faceted campaign effectiveness dish’s design for obtaining detection redshifted 21 cm emission from epoch reionization. Our show existence reflections between HERA’s suspended feed and its parabolic dish reflector that fall below −40 dB at 150 ns and, reasonable impedance matches, have negligible impact on ability...
In this article, we investigated the effect of Cr substitution in place Fe on structural, magnetic and transport properties $\mathrm{Co_2FeSi}$ alloy. A comprehensive structural analysis is done using X-ray diffraction (XRD) extended absorption fine structure (EXAFS) spectroscopy. Quaternary Heusler compounds $\mathrm{Co_2Fe_{1-x}Cr_xSi}$ with content (x = 0.1, 0.3, 0.5) were found to crystallize cubic structure. The synchrotron based EXAFS studies reveal that anti-site disorder increases...
The Square Kilometre Array Observatory (SKAO) will explore the radio sky to new depths in order conduct transformational science. SKAO data products made available astronomers be correspondingly large and complex, requiring application of advanced analysis techniques extract key science findings. To this end, is conducting a series Science Data Challenges, each designed familiarise scientific community with drive development techniques. We present results from Challenge 2 (SDC2), which...
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...
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...
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...
Interferometric experiments designed to detect the highly redshifted 21-cm signal from neutral hydrogen are producing increasingly stringent constraints on power spectrum, but some k-modes remain systematics-dominated. Mutual coupling is a major systematic that must be overcome in order signal, and simulations reproduce effects seen data can guide strategies for mitigating mutual coupling. In this paper, we analyse 12 nights of Hydrogen Epoch Reionization Array compare against include...
The 21 cm transition from neutral Hydrogen promises to be the best observational probe of Epoch Reionisation (EoR). This has led construction low-frequency radio interferometric arrays, such as Reionization Array (HERA), aimed at systematically mapping this emission for first time. Precision calibration, however, is a requirement in observations. Due spatial compactness HERA, array prone effects mutual coupling, which inevitably lead non-smooth calibration errors that contaminate data. When...