Jonathan C. Pober
A5026568310- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Antenna Design and Optimization
- Radio Wave Propagation Studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Superconducting and THz Device Technology
- Millimeter-Wave Propagation and Modeling
- Particle Accelerators and Free-Electron Lasers
- Electromagnetic Compatibility and Measurements
- Gamma-ray bursts and supernovae
- Soil Moisture and Remote Sensing
- Cosmology and Gravitation Theories
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Astronomical Observations and Instrumentation
- Scientific Research and Discoveries
- Computational Physics and Python Applications
- Astro and Planetary Science
- Telecommunications and Broadcasting Technologies
- Radio Frequency Integrated Circuit Design
- Advanced Wireless Communication Techniques
- Astrophysics and Star Formation Studies
- Advanced Measurement and Metrology Techniques
- Photonic and Optical Devices
John Brown University
2019-2025
Brown University
2015-2024
Software (Spain)
2019
University of Washington
2014-2016
Seattle University
2015
University of Washington Applied Physics Laboratory
2015
University of California, Berkeley
2011-2014
Haverford College
2007-2009
University of Cambridge
2008
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,...
A critical challenge in measuring the power spectrum of 21 cm emission from cosmic reionization is compensating for frequency dependence an interferometer's sampling pattern, which can cause smooth-spectrum foregrounds to appear unsmooth and degrade separation between target signal. In this paper, we present approach foreground removal that explicitly accounts dependence. We apply delay transformation introduced Parsons & Backer each baseline interferometer concentrate within bounds maximum...
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...
We present new constraints on the 21cm Epoch of Reionization (EoR) power spectrum derived from 3 months observing with a 32-antenna, dual-polarization deployment Donald C. Backer Precision Array for Probing (PAPER) in South Africa. In this paper, we demonstrate efficacy delay-spectrum approach to avoiding foregrounds, achieving over 8 orders magnitude foreground suppression (in $\textrm{mK}^2$). Combining procedure removing off-diagonal covariances arising instrumental systematics, achieve...
A number of experiments are currently working toward a measurement the 21 cm signal from epoch reionization (EoR). Whether or not these deliver detection cosmological emission, their limited sensitivity will prevent them providing detailed information about astrophysics reionization. In this work, we consider what types measurements be enabled by next generation larger EoR telescopes. To calculate type constraints that possible with such arrays, use simple models for instrument, foreground...
We compute the spherically-averaged power spectrum from four seasons of data obtained for Epoch Reionisation (EoR) project observed with Murchison Widefield Array (MWA). measure EoR over $k= 0.07-3.0~h$Mpc$^{-1}$ at redshifts $z=6.5-8.7$. The largest aggregation 110 hours on EoR0 high-band (3,340 observations), yields a lowest measurement (43~mK)$^2$ = 1.8$\times$10$^3$ mK$^2$ $k$=0.14~$h$Mpc$^{-1}$ and $z=6.5$ (2$\sigma$ thermal noise plus sample variance). Using Real-Time System to...
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...
The Arcminute Microkelvin Imager is a pair of interferometer arrays operating with six frequency channels spanning 13.9-18.2 GHz, very high sensitivity to angular scales 30''-10'. telescope aimed principally at Sunyaev-Zel'dovich imaging clusters galaxies. We discuss the design and describe explain its electronic mechanical systems.
We present new observations with the Precision Array for Probing Epoch of Reionization aim measuring properties foreground emission 21 cm epoch reionization (EoR) experiments at 150 MHz. focus on footprint foregrounds in cosmological Fourier space to understand which modes power spectrum will most likely be compromised by emission. These confirm predictions that can isolated a "wedge"-like region two-dimensional (k⊥, k∥)-space, creating window studies higher k∥ values. also find extends past...
Telescopes aiming to measure 21cm emission from the Epoch of Reionization must toe a careful line, balancing need for raw sensitivity against stringent calibration requirements removing bright foregrounds. It is unclear what optimal design achieving both these goals. Via pedagogical derivation an interferometer's response power spectrum reionization fluctuations, we show that even under optimistic scenarios, first-generation arrays will yield low-SNR detections, and different compact array...
21 cm epoch of reionization (EoR) observations promise to transform our understanding galaxy formation, but these are impossible without unprecedented levels instrument calibration. We present end-to-end simulations a full EoR power spectrum (PS) analysis including all the major components real data processing pipeline: models astrophysical foregrounds and signal, frequency-dependent effects, sky-based antenna calibration, PS analysis. This study reveals that traditional per-frequency...
Measurements of 21 cm Epoch Reionization (EoR) structure are subject to systematics originating from both the analysis and observation conditions. Using 2013 data Murchison Widefield Array (MWA), we show importance mitigating sources contamination. A direct comparison between results Beardsley et al. 2016 our updated demonstrates new precision techniques, lowering by a factor 2.8 in power. We then further lower excising observations contaminated ultra-faint RFI, reducing an additional 3.8...
ABSTRACT Cosmic Dawn (CD), when the first stars and proto-galaxies began to form, is commonly expected be accompanied by an absorption signature at radio frequencies. This feature arises as Lyman α photons emitted these luminous objects couple 21 cm excitation temperature of intergalactic hydrogen gas its kinetic temperature, driving it into relative cosmic microwave background. The detailed properties this profile encode powerful information about physics CD. Recently, Bowman et al....
We present first results from radio observations with the Murchison Widefield Array seeking to constrain power spectrum of 21 cm brightness temperature fluctuations between redshifts 11.6 and 17.9 (113 75 MHz). 3 h were conducted over two nights significantly different levels ionospheric activity. use these data assess impact systematic errors at low frequency, including ionosphere radio-frequency interference, on a measurement. find that after 1–3 integration presented here, our...
Abstract The compact configuration of Phase II the Murchison Widefield Array (MWA) consists both a redundant subarray and pseudo-random baselines, offering unique opportunities to perform sky-model interferometric calibration. highly hexagonal cores give improved power spectrum sensitivity. In this paper, we present analysis nearly 40 hr data targeting one MWA’s epoch reionization (EoR) fields observed in 2016. We use techniques presented Barry et al. several additional developed for work,...
This work describes a new instrument optimized for detection of the neutral hydrogen 21cm power spectrum between redshifts 0.5-1.5: Baryon Acoustic Oscillation Broadband and Broad-beam (BAOBAB) Array. BAOBAB will build on efforts first generation experiments which are targeting signal from Epoch Reionization at z ~ 10. At 1, emission in self-shielded overdense halos also presents an accessible signal, since dominant, synchrotron foreground is considerably fainter than redshift The principle...
Experiments aimed at detecting highly-redshifted 21 cm emission from the epoch of reionization (EoR) are plagued by contamination foreground emission. A potentially important source contaminating foregrounds may be Faraday-rotated, polarized emission, which leaks into estimate intrinsically unpolarized EoR signal. While these foregrounds' intrinsic polarization not problematic, spectral structure introduced Faraday rotation could be. To better understand and characterize effects, we present...
The epoch of reionization power spectrum is expected to evolve strongly with redshift, and it this variation cosmic history that will allow us begin place constraints on the physics reionization. primary obstacle measurement EoR bright foreground emission. We present an analysis observations from Donald C. Backer Precision Array for Probing Epoch Reionization (PAPER) telescope which new limits HI over redshift range $7.5<z<10.5$, extending previously published single results cover full...
Experiments that pursue detection of signals from the Epoch Reionization (EoR) are relying on spectral smoothness source spectra at low frequencies. This article empirically explores effect foreground EoR experiments by measuring high-resolution full-polarization for 586 brightest unresolved sources in one Murchison Widefield Array (MWA) fields using 45 h observation. A novel peeling scheme is used to subtract 2500 visibilities with ionospheric and beam corrections, resulting deepest,...
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...
Abstract The Epoch of Reionization (EoR) is an uncharted era in our universe’s history during which the birth first stars and galaxies led to ionization neutral hydrogen intergalactic medium. There are many experiments investigating EoR by tracing 21 cm line hydrogen. Because this signal very faint difficult isolate, it crucial develop analysis techniques that maximize sensitivity suppress contaminants data. It also imperative understand trade-offs between different methods their effects on...
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 Observations in the lowest Murchison Widefield Array (MWA) band between 75 and 100 MHz have potential to constrain distribution of neutral hydrogen intergalactic medium at redshift ∼13–17. Using 15 h MWA data, we analyse systematics this such as radio-frequency interference (RFI), ionospheric wide field effects. By updating position point sources, mitigate direction-independent calibration error due offsets. Our strategy is optimized for frequency bands by reducing number...
21 cm power spectrum observations have the potential to revolutionize our understanding of Epoch Reionization and Dark Energy, but require extraordinarily precise data analysis methods separate cosmological signal from astrophysical instrumental contaminants. This challenge has led a diversity proposed analyses, including delay spectra, imaging m-mode analysis, numerous others. approach is strength, also confusion within community about whether insights gleaned by one group are applicable...