ABOUT THIS COLLECTION

This open access archive contains publications from University of Arizona faculty, researchers and staff, primarily open-access versions of formally published journal articles. The collection includes published articles and final accepted manuscripts submitted by UA faculty under the UA Open Access Policy. The collection also includes books, book chapters, book reviews, presentations, data, and other scholarly materials submitters have chosen to make available in the repository.

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Recent Submissions

  • Complete genome characterization of cacao leafroll virus, a newly described cacao-infecting polerovirus

    Adegbola, Raphael O; Keith, Cory V; Gutierrez, Osman; Goenaga, Ricardo; Brown, Judith K; School of Plant Sciences, The University of Arizona (Springer, 2024-03-23)
    The complete genome sequence of cacao leafroll virus (CaLRV; family Solemoviridae, genus Polerovirus) was determined by high-throughput sequencing of total RNA isolated from symptomatic cacao Theobroma cacao L. plants (n = 4). The CaLRV genome sequences ranged from 5,976 to 5,997 nucleotides (nt) in length and contained seven open reading frames (ORFs). Nucleotide and amino acid (aa) sequence comparisons showed that, among selected well-characterized poleroviruses, the CaLRV genome shared the highest nt sequence identity of 62% with that of potato leafroll virus (PLRV, NC_076505). A comparison of the predicted aa sequence of the CaLRV coat protein indicated that cotton leafroll dwarf virus (CLRDV, NC_014545) and melon aphid-borne yellows virus (MABYV, NC_010809) were the closest relatives, sharing 57% aa sequence identity. Bayesian phylogenetic analysis based on complete genome sequences showed that CaLRV grouped with well-characterized poleroviruses that cause diseases of cereal and vegetable crops. During the course of publishing this work, the nearly complete genome sequence of a member of the same polerovirus species, referred to as “cacao polerovirus” (OR605721), with which CaLRV shares 99% nt sequence identity, was reported.
  • Insight into glacio-hydrologicalprocesses using explainable machine-learning (XAI) models

    Hao, Huiqing; Hao, Yonghong; Li, Zhongqin; Qi, Cuiting; Wang, Qi; Zhang, Ming; Liu, Yan; Liu, Qi; Jim Yeh, Tian-Chyi; Department of Hydrology and Atmospheric Sciences, The University of Arizona (Elsevier BV, 2024-03-11)
    The glacio-hydrological process is essential in the global water cycle but is complex and poorly understood. In this study, we couple the deep Shapley additive explanation (SHAP) with a long short-term memory (LSTM) model to construct a machine-learning (XAI) framework that describes the glacio-hydrological process in Urumqi Glacier No. 1, China. The XAI framework reveals 1) the dominant hydro-meteorological factors have a five-month lead time, and each factor has its own active time and degree of contribution; 2) the temperature and precipitation within the lead time dominate the process; 3) identifiable combination of the factors, instead of extreme events themselves, creates the extreme glacio-hydrological phenomena. Generally, the glacial meltwater replenishes the glacial stream runoff, which is influenced by many environmental factors. In particular, the runoff responds to the change in the glacier mass balance with hysteresis within five months. Overall, the temperature and precipitation within the lead time (4–5 months) dominate the runoff processes. This study quantifies the Contribution of each input in the glacio-hydrological process and provides valuable insight into the interaction of various hydro-meteorological factors.
  • The quality of teaching behaviors in learning environments of DHH students

    Rivera, M Christina; Catalano, Jennifer A; Branum-Martin, Lee; Lederberg, Amy R; Antia, Shirin D; Department of Disability and Psychoeducational Studies, University of Arizona (Oxford University Press, 2023-11-17)
    Classrooms are complex learning environments, with instruction, climate, and teacher–student interactions playing important roles in students’ academic progress. To investigate the learning environments of deaf and hard-of-hearing (DHH) students, we developed a new observational tool called the Quality of the Learning Environment-DHH rating scale (QLE-DHH) and rated 98 teachers of DHH students being educated in a range of classroom environments. The present study sought to (1) determine if the items on the QLE-DHH are good indicators of theoretically meaningful dimensions of classroom quality; (2) determine to what extent these dimensions predicted language and reading outcomes of DHH students; and (3) examine how teachers of DHH students were rated on the indicators of classroom quality. The findings suggested that the QLE-DHH has excellent structural validity. Ratings predicted student reading outcomes. Finally, the QLE-DHH was able to capture teachers’ strengths and skills in need of improvement. The QLE-DHH appears to hold promise for use in both research and teacher preparation programs.
  • Astrobiological Potential of Venus Atmosphere Chemical Anomalies and Other Unexplained Cloud Properties

    Petkowski, Janusz J.; Seager, Sara; Grinspoon, David H.; Bains, William; Ranjan, Sukrit; Rimmer, Paul B.; Buchanan, Weston P.; Agrawal, Rachana; Mogul, Rakesh; Carr, Christopher E.; et al. (Mary Ann Liebert Inc, 2024-04-10)
    Long-standing unexplained Venus atmosphere observations and chemical anomalies point to unknown chemistry but also leave room for the possibility of life. The unexplained observations include several gases out of thermodynamic equilibrium (e.g., tens of ppm O2, the possible presence of PH3 and NH3, SO2 and H2O vertical abundance profiles), an unknown composition of large, lower cloud particles, and the ''unknown absorber(s).'' Here we first review relevant properties of the venusian atmosphere and then describe the atmospheric chemical anomalies and how they motivate future astrobiology missions to Venus.
  • Simultaneous Drawing of Layered Trees

    Katheder, Julia; Kobourov, Stephen G.; Kuckuk, Axel; Pfister, Maximilian; Zink, Johannes; Department of Computer Science, University of Arizona (Springer Nature Singapore, 2024-02-29)
    We study the crossing-minimization problem in a layered graph drawing of planar-embedded rooted trees whose leaves have a given total order on the first layer, which adheres to the embedding of each individual tree. The task is then to permute the vertices on the other layers (respecting the given tree embeddings) in order to minimize the number of crossings. While this problem is known to be NP-hard for multiple trees even on just two layers, we describe a dynamic program running in polynomial time for the restricted case of two trees. If there are more than two trees, we restrict the number of layers to three, which allows for a reduction to a shortest-path problem. This way, we achieve XP-time in the number of trees.
  • Review of Open Software Bug Datasets

    Holek, Tomas; Bures, Miroslav; Cerny, Tomas; Systems and Industrial Engineering, University of Arizona (Springer Nature Switzerland, 2024-02-14)
    The localisation of the bug position in a source code and the prediction of which specific parts of a source code might be the cause of defects play an important role in maintaining software quality. Both approaches are based on applying information retrieval techniques and machine learning or deep learning methods. The prerequisite for using these approaches is the availability of a consistent bug dataset of sufficient size. This paper presents an overview of available public bug datasets and analyses their specific application areas. The paper also suggests possible future research directions in this field.
  • Pattern-Reconfigurable, Circularly Polarized, High-Gain, Archimedean Spiral Antenna Array for Long-distance, Wide-Coverage RFID Inventorying

    Yi, Da; Zhang, Ren-Long; Tang, Ming-Chun; Fu, Jing-Feng; Li, Yao; Li, Xing-Xing; Zhao, Huapeng; Ziolkowski, Richard W.; Department of Electrical and Computer Engineering, The University of Arizona (Institute of Electrical and Electronics Engineers (IEEE), 2024-03-20)
    A low-cost, pattern-reconfigurable, circularly polarized, high-gain, radio-frequency identification (RFID) reader antenna array is presented. It is a 2 × 2 array whose elements are based on an innovative Archimedean spiral design. A 4-way power divider feed network with switchable delay lines is designed that enables reconfiguring the radiation patterns of the array. Because of its high realized gain and nine reconfigurable states, the developed reader antenna can be applied in long-distance, wide-coverage RFID inventorying. The fabricated prototype, with dimensions 1.15 × 1.15 × 0.07 λL3 at 920 MHz, achieves a measured axial-ratio (AR) fractional bandwidth of 4.6%, and a peak realized gain (RG) of 10.5 dBic (12 dBic without the feed network). The RG of its reconfigurable patterns is greater than 6 dBic within θ = 0±45for all azimuth angles. It was also tested in an outdoor range as the reader antenna for a practical RFID system. The maximum read distance was 22.3 m.
  • Cumulative impacts in environmental justice: Insights from economics and policy

    Bakkensen, Laura A.; Ma, Lala; Muehlenbachs, Lucija; Benitez, Lina; School of Government and Public Policy, University of Arizona; Department of Agricultural and Resource Economics, University of Arizona (Elsevier BV, 2024-03-07)
    Disparities in health and socioeconomic well-being are a result of the cumulative impacts from multiple coinciding environmental, health, and social stressors. Addressing cumulative impacts is seen as a crucial step toward environmental justice (EJ). Using the case of the United States, we compare different methods to operationalize the concept for real-world application. We empirically demonstrate the extent to which non-White and low-income neighborhoods are subject to a wide array of burdens and how these burdens are reflected in national EJ indices and housing prices. We find that non-White and low-income neighborhoods are correlated with measures of multiple environmental burdens and social stressors but correlate to a lesser extent with natural disaster risk. Two existing EJ indices are only moderately correlated and more correlated with low-income status than with percent non-White. Models that employ the housing market for benefits estimation may fail to capture preferences to avoid multiple stressors due to issues including data availability and market frictions, such as discrimination. Finally, we highlight the challenges in cumulative impacts analysis for research and policy-making.
  • Honor among Crooks: The Role of Trust in Obfuscated Disreputable Exchange

    Schilke, Oliver; Rossman, Gabriel; The University of Arizona (SAGE Publications, 2024-03-16)
    When people want to conduct a transaction, but doing so would be morally disreputable, they can obfuscate the fact that they are engaging in an exchange while still arranging for a set of transfers that are effectively equivalent to an exchange. Obfuscation through structures such as gift-giving and brokerage is pervasive across a wide range of disreputable exchanges, such as bribery and sex work. In this article, we develop a theoretical account that sheds light on when actors are more versus less likely to obfuscate. Specifically, we report a series of experiments addressing the effect of trust on the decision to engage in obfuscated disreputable exchange. We find that actors obfuscate more often with exchange partners high in loyalty-based trustworthiness, with expected reciprocity and moral discomfort mediating this effect. However, the effect is highly contingent on the type of trust; trust facilitates obfuscation when it is loyalty-based, but this effect flips when trust is ethics-based. Our findings not only offer insights into the important role of relational context in shaping moral understandings and choices about disreputable exchange, but they also contribute to scholarship on trust by demonstrating that distinct forms of trust can have diametrically opposed effects.
  • An Ice Age JWST inventory of dense molecular cloud ices

    McClure, M. K.; Rocha, W. R. M.; Pontoppidan, K. M.; Crouzet, N.; Chu, L. E. U.; Dartois, E.; Lamberts, T.; Noble, J. A.; Pendleton, Y. J.; Perotti, G.; et al. (Springer Science and Business Media LLC, 2023-01-23)
    Icy grain mantles are the main reservoir of the volatile elements that link chemical processes in dark, interstellar clouds with the formation of planets and the composition of their atmospheres. The initial ice composition is set in the cold, dense parts of molecular clouds, before the onset of star formation. With the exquisite sensitivity of the James Webb Space Telescope, this critical stage of ice evolution is now accessible for detailed study. Here we show initial results of the Early Release Science programme Ice Age that reveal the rich composition of these dense cloud ices. Weak ice features, including 13CO2, OCN−, 13CO, OCS and complex organic molecule functional groups, are now detected along two pre-stellar lines of sight. The 12CO2 ice profile indicates modest growth of the icy grains. Column densities of the major and minor ice species indicate that ices contribute between 2% and 19% of the bulk budgets of the key C, O, N and S elements. Our results suggest that the formation of simple and complex molecules could begin early in a water-ice-rich environment.
  • StellarScape: An Immersive Multimedia Performance Inspired by the Life of a Star

    He, Yuanyuan (Kay); Impey, Chris; Burleson, Winslow; Fred Fox School of Music, University of Arizona; Steward Observatory, University of Arizona; School of Information, University of Arizona (MIT Press, 2023-06-01)
    StellarScape is an immersive multimedia performance synthesizing music, science, visual art, and technology. The performance includes live musicians, sensors, electronic music, and dance, all collaborating through interactive cinematography. The result combines kinesthetic and acoustic sensing with astrophysical simulations of star formation in real time. This convergence research collaboration is catalyzed by the union of concepts at the confluence of astronomy, humanity, artistic expression through music and dance, and sociotechnical experience. This article summarizes the authors’ motivation for undertaking the project, the interdisciplinary collaboration required to execute it, the authors’ goals for the audience experience, early results of the first performances, and ways the piece can be delivered in the future for entertainment, outreach, and education.
  • A reflective, metal-rich atmosphere for GJ 1214b from its JWST phase curve

    Kempton, Eliza M.-R.; Zhang, Michael; Bean, Jacob L.; Steinrueck, Maria E.; Piette, Anjali A. A.; Parmentier, Vivien; Malsky, Isaac; Roman, Michael T.; Rauscher, Emily; Gao, Peter; et al. (Springer Science and Business Media LLC, 2023-05-10)
    There are no planets intermediate in size between Earth and Neptune in our Solar System, yet these objects are found around a substantial fraction of other stars. Population statistics show that close-in planets in this size range bifurcate into two classes on the basis of their radii. It is proposed that the group with larger radii (referred to as `sub-Neptunes') is distinguished by having hydrogen-dominated atmospheres that are a few percent of the total mass of the planets. GJ 1214b is an archetype sub-Neptune that has been observed extensively using transmission spectroscopy to test this hypothesis. However, the measured spectra are featureless, and thus inconclusive, due to the presence of high-altitude aerosols in the planet's atmosphere. Here we report a spectroscopic thermal phase curve of GJ 1214b obtained with the James Webb Space Telescope (JWST) in the mid-infrared. The dayside and nightside spectra (average brightness temperatures of 553 ± 9 and 437 ± 19 K, respectively) each show more than 3σ evidence of absorption features, with H2O as the most likely cause in both. The measured global thermal emission implies that GJ 1214b's Bond albedo is 0.51 ± 0.06. Comparison between the spectroscopic phase curve data and three-dimensional models of GJ 1214b reveal a planet with a high metallicity atmosphere blanketed by a thick and highly reflective layer of clouds or haze.
  • DeScoD-ECG: Deep Score-Based Diffusion Model for ECG Baseline Wander and Noise Removal

    Li, Huayu; Ditzler, Gregory; Roveda, Janet; Li, Ao; Department of Electrical & Computer Engineering, The University of Arizona; Department of Biomedical Engineering, The University of Arizona; Bio5 Institute, The University of Arizona (Institute of Electrical and Electronics Engineers (IEEE), 2023-01-17)
    Abstract—Objective: Electrocardiogram (ECG) signals commonly suffer noise interference, such as baseline wander. Highquality and high-fidelity reconstruction of the ECG signals is of great significance to diagnosing cardiovascular diseases. Therefore, this paper proposes a novel ECG baseline wander and noise removal technology. Methods: We extended the diffusion model in a conditional manner that was specific to the ECG signals, namely the Deep Score-Based Diffusion model for Electrocardiogram baseline wander and noise removal (DeScoD-ECG). Moreover, we deployed a multi-shots averaging strategy that improved signal reconstructions. We conducted the experiments on the QT Database and the MIT-BIH Noise Stress Test Database to verify the feasibility of the proposed method. Baseline methods are adopted for comparison, including traditional digital filterbased and deep learning-based methods. Results: The quantities evaluation results show that the proposed method obtained outstanding performance on four distance-based similarity metrics with at least 20% overall improvement compared with the best baseline method. Conclusion: This paper demonstrates the stateof-the-art performance of the DeScoD-ECG for ECG baseline wander and noise removal, which has better approximations of the true data distribution and higher stability under extreme noise corruptions. Significance: This study is one of the first to extend the conditional diffusion-based generative model for ECG noise removal, and the DeScoD-ECG has the potential to be widely used in biomedical applications. Index Terms—ECG signal processing, Baseline wander, diffusion models
  • Contrasting effects of biochar application rate in an alkaline desert cropland soil

    Hoglund, Shelby R.; Rathke, Samuel J.; Fidel, Rivka B.; Blankinship, Joseph C.; Department of Environmental Science, University of Arizona (Elsevier BV, 2023-06-04)
    Improving water and nutrient retention in desert croplands using soil organic amendments can be a major challenge because organic matter decomposes quickly under irrigated conditions in a hot climate. Biochar—a long-lasting carbon-rich soil organic amendment—has been proposed to improve soil water and nutrient retention, but only by carefully selecting an appropriate application rate. To better understand effects of biochar application rate on soil water and nutrient retention in desert croplands, we set up a mesocosm-scale experiment with biochar added at rates of 0, 19.8, 39.7, 79.4, 119.0, and 158.7 t ha−1 to an alkaline, sandy loam soil. After initial water retention measurements, we added fertilizer and then measured gaseous nitrogen losses as well as soil nitrate (NO3−) and phosphate (PO₄³⁻) leaching. Then, we measured biochar's effect on the soil's capacity to hold plant-available water (i.e., available water capacity, or AWC) using Tempe cells and a dewpoint potentiometer. We found contrasting effects of low and high biochar application rates. First, we found that applying a minimum of 79.4 t ha−1 biochar was necessary to improve soil water and PO₄³⁻ retention; application rates below 79.4 t ha−1 exacerbated PO₄³⁻ leaching whereas treatments above 79.4 t ha−1 improved AWC by up to 34% compared to the control treatment. While biochar application rate did not affect soil nitric oxide or ammonia emissions, we did find that low biochar application rates increased soil nitrous oxide emission while higher application rates reduced emission compared to soil with no biochar. Overall, we found that lower and higher rates of biochar application can have contrasting effects on soil water and nutrient retention in an alkaline, desert cropland soil. Therefore, farmers and other land managers must consider potential drawbacks of lower application rates and threshold responses of higher application rates prior to large-scale biochar use in arid agroecosystems.
  • A Call for the United States to Accelerate the Implementation of Reliever Combination Inhaled Corticosteroid-Formoterol Inhalers in Asthma

    Krings, James G; Gerald, Joe K; Blake, Kathryn V; Krishnan, Jerry A; Reddel, Helen K; Bacharier, Leonard B; Dixon, Anne E; Sumino, Kaharu; Gerald, Lynn B; Brownson, Ross C; et al. (The American Thoracic Society (ATS), 2023-02-15)
    Asthma management has undergone a paradigm shift that is underutilized by real-world clinicians, particularly in the United States (US). Trials containing approximately 30,000 patients over 20 years have demonstrated the benefits of new inhaler approaches. In mild asthma, reliever usage of an inhaled corticosteroid (ICS) with formoterol (a unique rapid-onset long-acting β-agonist) provides quick symptom relief and is substantially more effective at preventing asthma exacerbations than short-acting β-agonist (SABA) monotherapy. In moderate/severe asthma using an ICS-formoterol inhaler on both a maintenance and reliever basis (single maintenance and reliever therapy [SMART]) is more effective at preventing severe exacerbations than traditional asthma management. As a result, the Global Initiative for Asthma (GINA) now calls for the preferential use of ICS-formoterol inhalers on a reliever basis at all steps of management. The US-based National Asthma Education and Prevention Program (NAEPP) guideline published in 2020 did not review as-needed ICS-formoterol in mild asthma, but similarly recommends SMART at Steps 3-4 within their management paradigm. In this article we review the latest asthma recommendations and the rationale for the recommendation/guideline changes. We then acknowledge and name the barriers to utilizing these new inhaler approaches that exist in real-world practice, particularly in the US. Using the tools of implementation science, we call for the asthma field to urgently work to ameliorate these barriers . Finally, while admittedly controversial, we call for consideration of the prescription-to-over-the-counter transition of low-dose budesonide formoterol in the US. This transition could expand medication access, reduce unopposed use of SABAs, and provide a more acceptable safety net for patients, as compared to aerosolized epinephrine, which is currently the only available OTC reliever inhaler in the US.
  • High atmospheric metal enrichment for a Saturn-mass planet

    Bean, Jacob L; Xue, Qiao; August, Prune C; Lunine, Jonathan; Zhang, Michael; Thorngren, Daniel; Tsai, Shang-Min; Stassun, Keivan G; Schlawin, Everett; Ahrer, Eva-Maria; et al. (Nature Research, 2023-03-27)
    Atmospheric metal enrichment (that is, elements heavier than helium, also called 'metallicity') is a key diagnostic of the formation of giant planets1-3. The giant planets of the Solar System show an inverse relationship between mass and both their bulk metallicities and atmospheric metallicities. Extrasolar giant planets also display an inverse relationship between mass and bulk metallicity4. However, there is significant scatter in the relationship and it is not known how atmospheric metallicity correlates with either planet mass or bulk metallicity. Here we show that the Saturn-mass exoplanet HD 149026b (refs. 5-9) has an atmospheric metallicity 59-276 times solar (at 1σ), which is greater than Saturn's atmospheric metallicity of roughly 7.5 times solar10 at more than 4σ confidence. This result is based on modelling CO2 and H2O absorption features in the thermal emission spectrum of the planet measured by the James Webb Space Telescope. HD 149026b is the most metal-rich giant planet known, with an estimated bulk heavy element abundance of 66 ± 2% by mass11,12. We find that the atmospheric metallicities of both HD 149026b and the Solar System giant planets are more correlated with bulk metallicity than planet mass.
  • Earth system justice needed to identify and live within Earth system boundaries

    Gupta, Joyeeta; Liverman, Diana; Prodani, Klaudia; Aldunce, Paulina; Bai, Xuemei; Broadgate, Wendy; Ciobanu, Daniel; Gifford, Lauren; Gordon, Chris; Hurlbert, Margot; et al. (Springer Science and Business Media LLC, 2023-03-02)
    Living within planetary limits requires attention to justice as biophysical boundaries are not inherently just. Through collaboration between natural and social scientists, the Earth Commission defines and operationalizes Earth system justice to ensure that boundaries reduce harm, increase well-being, and reflect substantive and procedural justice. Such stringent boundaries may also affect ‘just access’ to food, water, energy and infrastructure. We show how boundaries may need to be adjusted to reduce harm and increase access, and challenge inequality to ensure a safe and just future for people, other species and the planet. Earth system justice may enable living justly within boundaries.
  • High-resolution [O I] line spectral mapping of TW Hya supportive of a magnetothermal wind

    Fang, Min; Wang, Lile; Herczeg, Gregory J.; Hashimoto, Jun; Xu, Ziyan; Nemer, Ahmad; Pascucci, Ilaria; Haffert, Sebastiaan Y.; Aoyama, Yuhiko; Department of Planetary Sciences, University of Arizona; et al. (Springer Science and Business Media LLC, 2023-06-19)
    Disk winds are thought to play a critical role in the evolution and dispersal of protoplanetary disks. A primary diagnostic of this physics is emission from the wind, especially in the low-velocity component of the [O I] λ6,300 line. However, the interpretation of the line is usually based on spectroscopy alone, which leads to confusion between magnetohydrodynamic winds and photoevaporative winds. Here we report that in high-resolution spectral mapping of TW Hya by the multi-unit spectroscopic explorer at the Very Large Telescope, 80% of the [O I] emission is confined to within 1 au radially from the star. A generic model of a magnetothermal wind produces [O I] emission at the base of the wind that broadly matches the flux and the observed spatial and spectral profiles. The emission at large radii is much fainter than predicted from models of photoevaporation, perhaps because the magnetothermal wind partially shields the outer disk from energetic radiation from the central star. This result calls into question the previously assessed importance of photoevaporation in disk dispersal predicted by models.
  • Identification and properties of intense star-forming galaxies at redshifts z > 10

    Robertson, B. E.; Tacchella, S.; Johnson, B. D.; Hainline, K.; Whitler, L.; Eisenstein, D. J.; Endsley, R.; Rieke, M.; Stark, D. P.; Alberts, S.; et al. (Springer Science and Business Media LLC, 2023-04-04)
    Surveys with the James Webb Space Telescope (JWST) have discovered candidate galaxies in the first 400 Myr of cosmic time. Preliminary indications have suggested these candidate galaxies may be more massive and abundant than previously thought. However, without confirmed distances, their inferred properties remain uncertain. Here we identify four galaxies located in the JWST Advanced Deep Extragalactic Survey Near-Infrared Camera imaging with photometric redshifts z of roughly 10–13. These galaxies include the first redshift z > 12 systems discovered with distances spectroscopically confirmed by JWST in a companion paper. Using stellar population modelling, we find the galaxies typically contain 100 million solar masses in stars, in stellar populations that are less than 100 million years old. The moderate star-formation rates and compact sizes suggest elevated star-formation rate surface densities, a key indicator of their formation pathways. Taken together, these measurements show that the first galaxies contributing to cosmic reionization formed rapidly and with intense internal radiation fields.
  • Inspiraling streams of enriched gas observed around a massive galaxy 11 billion years ago

    Zhang, Shiwu; Cai, Zheng; Xu, Dandan; Shimakawa, Rhythm; Arrigoni Battaia, Fabrizio; Prochaska, Jason Xavier; Cen, Renyue; Zheng, Zheng; Wu, Yunjing; Li, Qiong; et al. (American Association for the Advancement of Science, 2023-05-04)
    A tidal disruption event (TDE) occurs when a supermassive black hole rips apart a passing star. Part of the stellar material falls toward the black hole, forming an accretion disk that in some cases launches a relativistic jet. We performed optical polarimetry observations of a TDE, AT 2020mot. We find a peak linear polarization degree of 25 ± 4%, consistent with highly polarized synchrotron radiation, as is typically observed from relativistic jets. However, our radio observations, taken up to 8 months after the optical peak, do not detect the corresponding radio emission expected from a relativistic jet. We suggest that the linearly polarized optical emission instead arises from shocks that occur during accretion disk formation, as the stream of stellar material collides with itself.

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