About

Judd Bowman is an experimental astrophysicist exploring the birth of cosmic structure in the early universe, including the first stars, galaxies, and black holes. He holds the Beus Chair of Cosmology and serves as the Director of the Beus Center for Cosmic Foundations in the School of Earth and Space Exploration at ASU. His research focuses on developing advanced radio instrumentation and techniques to detect the faint redshifted 21 cm signal emitted by neutral hydrogen during the epoch of reionization. His work has been recognized as one of the Top 10 Breakthroughs of the Year in 2018 by Physics World. Professor Bowman leads the EDGES experiment in Western Australia and is designing next-generation radio telescope concepts for deployment on the far side of the Moon. He has also led the development and operation of ASU's first cubesat, Phoenix, deployed from the International Space Station in 2020. Currently, he is constructing a new radio telescope near Meteor Crater outside Flagstaff, Arizona, scheduled for completion in 2026. His research involves creating novel algorithms and software to enhance observations with ground-based instruments and small spacecraft, contributing significantly to the field of cosmology and radio astronomy.

Research topics

• Astrophysics
• Physics
• Astronomy
• Particle physics

Selected publications

• Results from the investigation of temporal discontinuity in the Hydrogen Epoch of Reionization Array data

  RAS Techniques and Instruments · 2026-01-01

  articleOpen access

  ABSTRACT We report systematic issues commonly observed in the Hydrogen Epoch of Reionization Array observations that cause abrupt changes in power over time, resulting in temporal discontinuities. To identify these effects, we applied the Temporal Discontinuity Index and Spectral Discontinuity Index metrics, which complement existing diagnostic tools by detecting discontinuities and revealing their potential relationships to bandpass and power-related issues. Analysis of 30 data sets, each corresponding to a single observing night, shows that such systematics appear consistently in many antennas and across multiple nights. Based on these metrics, we identify three main types of discontinuity-related issues: periodic broad-band discontinuities linked to Inter-Integrated Circuit (I2C) polling, broad-band discontinuities associated with degraded post-amplifier modules (PAMs), and sudden power changes related to the digital backend of the antenna system. The second type, associated with degraded PAMs, occurs less frequently within a single night compared to the periodic polling effect, though both are broadband. The third type affects the largest number of antennas and is most prevalent in the H6C data. The width of the discontinuities related to the digital backend corresponds to the frequency range handled by a single correlator box, scaled by the number of boxes involved. Although 30 data sets were examined, this paper presents a focused analysis of four representative nights to highlight the main discontinuity issues. We also present correlations between flagging due to discontinuities and flagging caused by other failure modes to investigate how these issues are interrelated.

  PublisherDOI

• A general Bayesian model-validation framework based on null-test evidence ratios, with an example application to global 21-cm cosmology

  Monthly Notices of the Royal Astronomical Society · 2025-07-08 · 3 citations

  articleOpen access

  ABSTRACT Comparing composite models for multicomponent observational data is a prevalent scientific challenge. When fitting composite models, there exists the potential for systematics from a poor fit of one model component to be absorbed by another, resulting in the composite model providing an accurate fit to the data in aggregate but yielding biased a posteriori estimates for individual components. We begin by defining a classification scheme for composite model comparison scenarios, identifying two categories: category I, where models with accurate and predictive components are separable through Bayesian comparison of the unvalidated composite models, and category II, where models with accurate and predictive components may not be separable due to interactions between components, leading to spurious detections or biased signal estimation. To address the limitations of category II model comparisons, we introduce the Bayesian Null Test Evidence Ratio-based (BaNTER) validation framework. Applying this classification scheme and BaNTER to a composite model comparison problem in 21-cm cosmology, where minor systematics from imperfect foreground modelling can bias global 21-cm signal recovery, we validate six composite models using mock data. We show that incorporating BaNTER alongside Bayes-factor-based comparison reliably ensures unbiased inferences of the signal of interest across both categories, positioning BaNTER as a valuable addition to Bayesian inference workflows with potential applications across diverse fields.

  PublisherOA PDFDOI

• Creating Reliable Software Systems for the DORA CubeSat

  Digital Commons - USU (Utah State University) · 2025-08-07

  articleOpen access

  The Deployable Optical Receiver Aperture (DORA) CubeSat is a 3U CubeSat that seeks to demonstrate data rates of 1 Gbps over distances of thousands. The DORA technology presents an easy to accommodate optical communications solution for smallsats, which previously was limited by the high pointing accuracy requirement for traditional optical communication systems. We believe this technology to be best suited for surface to orbit communications and the crosslink between small spacecraft, including those in smallsat constellations/swarms.

  PublisherOA PDFDOI

• A Bayesian approach to modelling spectrometer data chromaticity corrected using beam factors – II. Model priors and posterior odds

  Monthly Notices of the Royal Astronomical Society · 2025-10-15 · 2 citations

  articleOpen access

  ABSTRACT The reliable detection of the global 21-cm signal, a key tracer of Cosmic Dawn and the Epoch of Reionization, requires meticulous data modelling and robust statistical frameworks for model validation and comparison. In Paper I of this series, we presented the beam-factor-based chromaticity correction (BFCC) model for spectrometer data processed using BFCC to suppress instrumentally induced spectral structure. We demonstrated that the BFCC model, with complexity calibrated by Bayes factor-based model comparison (BFBMC), enables unbiased recovery of a 21-cm signal consistent with the one reported by The Experiment to Detect the Global Epoch of Reionization Signature (EDGES) from simulated data. Here, we extend the evaluation of the BFCC model to lower amplitude 21-cm signal scenarios where deriving reliable conclusions about a model’s capacity to recover unbiased 21-cm signal estimates using BFBMC is more challenging. Using realistic simulations of chromaticity-corrected EDGES-low spectrometer data, we evaluate three signal amplitude regimes – null, moderate, and high. We then conduct a Bayesian comparison between the BFCC model and three alternative models previously applied to 21-cm signal estimation from EDGES data. To mitigate biases introduced by systematics in the 21-cm signal model fit, we incorporate the Bayesian Null-Test-Evidence-Ratio (BaNTER) validation framework and implement a Bayesian inference workflow based on posterior odds of the validated models. The BaNTER-validated posterior-odds-based methodology presented here is general and transferable to other global 21-cm experiments employing Bayesian signal inference. We demonstrate that, unlike BFBMC alone, this approach consistently recovers 21-cm signal estimates that align with the true signal across all amplitude regimes, advancing robust global 21-cm signal detection methodologies.

  PublisherOA PDFDOI

• Measuring the Magnetic Field of a Coronal Mass Ejection from the Low to Middle Corona

  The Astrophysical Journal Letters · 2025-09-04 · 5 citations

  articleOpen accessCorresponding

  Abstract A major challenge in understanding the initiation and evolution of coronal mass ejections (CMEs) is measuring the magnetic field of the magnetic flux ropes (MFRs) that drive CMEs. Recent developments in radio imaging spectroscopy have paved the way for diagnosing the CMEs’ magnetic field using gyrosynchrotron radiation. We present magnetic field measurements of a CME associated with an X5-class flare by combining radio imaging spectroscopy data in microwaves (1–18 GHz) and meter waves (20–88 MHz), obtained by the Owens Valley Radio Observatory’s Expanded Owens Valley Solar Array (EOVSA) and Long Wavelength Array (OVRO-LWA), respectively. EOVSA observations reveal that the microwave source, observed in the low corona during the initiation phase of the eruption, outlines the bottom of the rising MFR-hosting CME bubble seen in extreme ultraviolet and expands as the bubble evolves. As the MFR erupts into the middle corona and appears as a white-light CME, its meter-wave counterpart, observed by OVRO-LWA, displays a similar morphology. For the first time, using gyrosynchrotron spectral diagnostics, we obtain magnetic field measurements of the erupting MFR in both the low and middle corona, corresponding to coronal heights of 0.02 and 1.83 R ⊙ . The magnetic field strength is found to be around 300 G at 0.02 R ⊙ during the CME initiation and about 0.6 G near the leading edge of the CME when it propagates to 1.83 R ⊙ . These results provide critical new insights into the magnetic structure of the CME and its evolution during the early stages of its eruption.

  PublisherDOI

• Probing the Turbulent Corona and Heliosphere Using Radio Spectral Imaging Observation during the Solar Conjunction of the Crab Nebula

  The Astrophysical Journal · 2025-10-09 · 2 citations

  articleOpen access

  Abstract Measuring plasma parameters in the upper solar corona and inner heliosphere is challenging because of the region’s weakly emissive nature and inaccessibility for most in situ observations. Radio imaging of broadened and distorted background astronomical radio sources during solar conjunction can provide unique constraints for the coronal material along the line of sight. In this study, we present radio spectral imaging observations of the Crab Nebula (Tau A) from 2024 June 9 to June 22 when it was near the Sun with a projected heliocentric distance of 5–27 solar radii, using the Owens Valley Radio Observatory’s Long Wavelength Array at multiple frequencies in the 30–80 MHz range. The imaging data reveal frequency-dependent broadening and distortion effects caused by anisotropic wave propagation through the turbulent solar corona at different distances. We analyze the brightness, size, and anisotropy of the broadened images. Our results provide detailed observations showing that the eccentricity of the unresolved source increases as the line of sight approaches the Sun, suggesting a higher anisotropic ratio of the plasma turbulence closer to the Sun. In addition, the major axis of the elongated source is consistently oriented in the direction perpendicular to the radial direction, suggesting that the turbulence-induced scattering effect is more pronounced in the direction transverse to the coronal magnetic field. Lastly, when the source undergoes large-scale refraction as the line of sight passes through a streamer, the apparent source exhibits substructures at lower frequencies. This study demonstrates that observations of celestial radio sources with lines of sight near the Sun provide a promising method for measuring turbulence parameters in the inner heliosphere.

  PublisherDOI

• Investigating mutual coupling in the hydrogen epoch of reionization array and mitigating its effects on the 21-cm power spectrum

  Monthly Notices of the Royal Astronomical Society · 2025-06-27 · 7 citations

  articleOpen access

  ABSTRACT Interferometric experiments designed to detect the highly redshifted 21-cm signal from neutral hydrogen are producing increasingly stringent constraints on the 21-cm power spectrum, but some k-modes remain systematics-dominated. Mutual coupling is a major systematic that must be overcome in order to detect the 21-cm signal, and simulations that reproduce effects seen in the data can guide strategies for mitigating mutual coupling. In this paper, we analyse 12 nights of data from the Hydrogen Epoch of Reionization Array and compare the data against simulations that include a computationally efficient and physically motivated semi-analytic treatment of mutual coupling. We find that simulated coupling features qualitatively agree with coupling features in the data; however, coupling features in the data are brighter than the simulated features, indicating the presence of additional coupling mechanisms not captured by our model. We explore the use of fringe-rate filters as mutual coupling mitigation tools and use our simulations to investigate the effects of mutual coupling on a simulated cosmological 21-cm power spectrum in a ‘worst case’ scenario where the foregrounds are particularly bright. We find that mutual coupling contaminates a large portion of the ‘EoR Window’, and the contamination is several orders-of-magnitude larger than our simulated cosmic signal across a wide range of cosmological Fourier modes. While our fiducial fringe-rate filtering strategy reduces mutual coupling by roughly a factor of 100 in power, a non-negligible amount of coupling cannot be excised with fringe-rate filters, so more sophisticated mitigation strategies are required.

  PublisherOA PDFDOI

• Improved Limits on the 21 cm Signal at <i>z</i> = 6.5–7.0 with the Murchison Widefield Array Using Gaussian Information

  The Astrophysical Journal · 2025-09-30

  articleOpen access

  Abstract We explore the properties of interferometric data from high-redshift 21 cm measurements using the Murchison Widefield Array (MWA). These data contain the redshifted 21 cm signal, contamination from continuum foreground sources, and radiometric noise. The 21 cm signal from the Epoch of Reionization (EoR) is expected to be highly Gaussian, which motivates the use of the power spectrum as an effective statistical tool for extracting astrophysical information. We find that foreground contamination introduces non-Gaussianity into the distribution of measurements and then use this information to separate Gaussian from the non-Gaussian signal. We present improved upper limits on the 21 cm EoR power spectrum from the MWA using a Gaussian component of the data, based on the existing analysis from C. D. Nunhokee et al. 2025. This is extracted as the best-fitting Gaussian to the measured data. Our best 2 σ (thermal+sample variance) limit for 268 hr of data improves from (30.2 mK) 2 to (23.0 mK) 2 at z = 6.5 for the East–West polarization, and from (39.2 mK) 2 to (21.7 mK) 2 = 470 mK 2 in North–South. The best limits at z = 6.8 ( z = 7.0) improve to P &lt; (25.9 mK) 2 ( P &lt; (32.0 mK) 2 ) and k = 0.18 h Mpc −1 ( k = 0.21 h Mpc −1 ). Results are compared with realistic simulations, which indicate that leakage from foreground contamination is a source of the non-Gaussian behavior.

  PublisherDOI

• High energy cosmic ray detections with the standalone radio trigger system at the Owens Valley Radio Observatory Long Wavelength Array

  2025-09-24

  articleOpen access

  Radio observations of cosmic ray air showers can characterize cosmic ray mass composition, via precise Xmax measurements, at the energies of the likely shift from Galactic to extragalactic sources. Advantages over other methods include lower cost instrumentation and the ability to observe in a range of weather conditions. However, detecting cosmic rays via their radio emission alone amid radio frequency interference (RFI), without reference to an alternate particle detector, is a significant challenge. The Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) cosmic ray detection system uses a multistage RFI rejection process including FPGA and CPU processing to address this challenge and operate in the presence of RFI. The OVRO-LWA is a multi-use array of 352 dual-polarization dipole antennas operating at ~30—80 MHz. The array recently completed a major upgrade, including the addition of the cosmic ray detection system, which operates simultaneously with the other radio astronomy observing modes. Detections of cosmic ray candidates began in 2024. The dense antenna spacing of the OVRO-LWA offers the opportunity for testing and developing new Xmax reconstruction techniques, such as interferometric reconstruction. This presentation will describe the cosmic ray detection system, present the sample of cosmic ray candidates, and discuss plans for the future.

  PublisherOA PDFDOI

• Deployable Optical Receiver Array Cubesat

  Digital Commons - USU (Utah State University) · 2025-08-11 · 2 citations

  articleOpen access

  Small satellites and cubesats often have low data transmission rates due to the use of low-gain radio links in UHF and S bands. These links typically provide up to only 1 Mbps for communication between the ground and LEO, limiting the applications and mission operations of small satellites. Optical communication technology can enable much higher data rates and is rapidly gaining hold for larger satellites, including for crosslinks within SpaceX’s Starlink constellation and upcoming NASA deep space missions. However, it has been difficult to implement on small satellites and cubesats due to the need for precision pointing on the order of arcseconds to align the narrow optical laser beam between terminals--a laser transmitter in LEO may yield a footprint less than 100 meters wide at its receiving ground station. We report the development of a 3U cubesat to demonstrate new optical communication technology that eliminates precision pointing accuracy requirements on the host spacecraft. The deployable optical receiver aperture (DORA) aims to demonstrate 1 Gbps data rates over distances of thousands of kilometers. DORA requires an easily accommodated host pointing accuracy of only 10 degrees with minimal stability, allowing the primary mission to continue without reorienting to communicate and/or enabling small satellite missions using low-cost off-the-shelf ADCS systems. To achieve this performance, DORA replaces the traditional receiving telescope on the spacecraft with a collection of wide-angle photodiodes that can identify the angle of arrival for incoming communication lasers and steer the onboard transmitting laser in the corresponding direction. This work is motivated by NASA’s plans for a lunar communications and navigation network and supported by NASA’s Space Technology Program (STP). It is ideally suited for crosslink communications among small spacecraft, especially for those forming a swarm and/or a constellation, and for surface to orbit communications. We will implement the deployable optical receiver aperture and miniature transmission telescope as a 1U payload in the 3U cubesat and conduct the demonstration flight in LEO. Future implementations of the DORA technology are expected to further enable omnidirectional receiving of multiple optical communications simultaneously and accommodate multiple transmitting modules on a single cubesat.

  PublisherOA PDFDOI

Recent grants

• Collaborative Research: Detecting the First Light and Reionization of the Universe using Advanced Radio Instrumentation

  NSF · $621k · 2016–2020

• COLLABORATIVE RESEARCH: Observing the Epoch of Reionization with the Murchison Widefield Array

  NSF · $201k · 2014–2017

• Collaborative Research: EDGES-3: Validating and Refining Global 21cm Measurements of Cosmic Dawn

  NSF · $599k · 2019–2024

• First Deployment of a Novel Imaging Correlator for Radio Astronomy with the Long Wavelength Array

  NSF · $473k · 2017–2022

• Facilitating Museum Evaluation with Real-Time Data Mining

  NSF · $798k · 2014–2018

Frequent coauthors

• S. J. Tingay

  Curtin University

  264 shared

• G. Bernardi

  Istituto di Radioastronomia di Bologna

  255 shared

• R. B. Wayth

  247 shared

• D. A. Mitchell

  240 shared

• R. L. Webster

  190 shared

• S. M. Ord

  185 shared

• M. F. Morales

  184 shared

• B. J. Hazelton

  165 shared

Labs

• Beus Center for Cosmic FoundationsPI

  Brings together observational and theoretical astrophysicists, educators, instrument builders, and engineers to advance our knowledge of the formation and evolution of stars and galaxies.

Education

• B.S.

  Washington University in St. Louis

  1998

• B.S.

  Washington University in St. Louis

  1998

• Ph.D.

  Massachusetts Institute of Technology

  2007

Awards & honors

• Physics World Top 10 Breakthroughs of the Year (2018)