Physics Commons^™

First Results On The Search For Lepton Number Violating Neutrinoless Double-Β Decay With The Legend-200 Experiment, H. Acharya, N. Ackermann, M. Agostini, A. Alexander, C. Andreoiu, G. R. Araujo, Frank Avignone Iii, M. Babicz, W. Bae, A. M. Bakalyarov, M. Balata, A. S. Barabash, C. J. Barton, L. Baudis, C. Bauer, E. Bernieri, L. Bezrukov, K. H. Bhimani, V. Biancaccu, E. Blalock, Et. Al.

Faculty Publications

The LEGEND Collaboration is searching for neutrinoless double-beta (0νββ) decay by operating high-purity germanium detectors enriched in ⁷⁶Ge in a low-background liquid argon environment. Building on key technological innovations from the GERmanium Detector Array (GERDA) experiment and the MAJORANA DEMONSTRATOR experiment, LEGEND-200 has performed a first 0νββ decay search based on 61.0 kg yr of data. Over half of this exposure comes from our highest performing detectors, including newly developed inverted-coaxial detectors, and is characterized by an estimated background level of 0.5^+0.3_−0.2 cts/(keV ton yr) in the 0νββ decay signal region. A combined …

Proposed Methodology For Correcting Fourier-Transform Infrared Spectroscopy Field-Of-View Scene-Change Artifacts, Kody A. Wilson, Michael L. Dexter, Benjamin F. Akers, Anthony L. Franz

Faculty Publications

Fourier-transform spectrometers are widely used for spectral measurements. Changes in the field of view during measurement introduce oscillations into the measured spectra known as scene-change artifacts. Field-of-view changes also introduce uncertainty about which target the measured spectrum represents. Though scene-change artifacts are often present in dynamic data, their significance is disputed in the current literature. This work presents a theoretical framework and experimental validation for scene-change artifacts. Field-of-view changes introduce variable interferogram offsets, which standard processing techniques assume are constant. The error between the interferogram offset and its estimate is Fourier-transformed, yielding scene-change artifacts, often confused with noise, in the …

Improving Stem Assessments: Strategies For Increasing The Accessibility And Adoption Of Two-Stage Exams, Kristina Callaghan

LSU Doctoral Dissertations

Over three decades of research have shown that students taught using active learning strategies achieve better learning outcomes compared to those taught using traditional methods. Two-stage exams, which pair a traditional exam with a group component, are an increasingly popular method for incorporating active learning within the assessment component of a course. Previous studies have shown this assessment strategy provides a variety of benefits for students, including increased engagement and collaboration, immediate feedback, and potentially increased content retention. However, the unique circumstances of each instructor can pose a non-trivial barrier to the implementation of two-stage exams. In this thesis, we …

Spectroscopic Investigations On Polyvinylidene Fluoride Nanofibers, Parinaz Amaniabdolmalaki, Jui Vitthal Kharade, Alexandro Trevino, Lydia Morales, Karen Lozano, Victoria Padilla, Karen S. Martirosyan, Horacio Vasquez, Mircea Chipara

Physics & Astronomy Faculty Publications

The production of polyvinylidene fluoride nanofibers by force-spinning from polymer solutions was confirmed by electron microscopy. The structural and phase characteristics of the resulting nanofiber mats were examined using Fourier Transform Infrared Spectroscopy in Attenuated Total Reflectance mode, Raman spectroscopy, and X-ray Diffraction. Results from all these techniques consistently indicated that both the powder and the mats of polyvinylidene fluoride predominantly contain the α phase, with a small admixture of the β phase. Within experimental errors, no other phases were noticed both in the powder and in the as-obtained mats. The ratios of the areas of the Raman lines at …

High Thermoelectric Power Conversion Efficiency Of An Earth-Abundant Janus Silicon Oxy-Sulfide Monolayer: A First-Principles Study, Zakariae Darhi, Mounaim Bencheikh, Ravindra Pandey, Larbi El Farh

Michigan Tech Publications

The tunable properties of Janus monolayers, along with advances in their synthesis, make these low-symmetry materials excellent candidates for thermoelectric power generation. In this study, we systematically investigate the electronic and thermal properties of the Janus silicon oxy-sulfide monolayer. The results based on density functional theory reveal that the monolayer is stable. It exhibits a tunable direct band gap and strong covalent bonding. Its ultralow lattice thermal conductivity (< 0.38 W mK⁻¹ at 300 K) is attributed to the broken phonon selection rule for phonon–phonon scattering and a high level of anharmonicity, as reflected in the large Grüneisen parameter. Furthermore, the inclusion …

Jwst Interferometric Imaging Reveals The Dusty Torus Obscuring The Supermassive Black Hole Of Circinus Galaxy, Enrique Lopez Rodriguez, Joel Sanchez-Bermudez, Omaira González-Martín, Robert Nikutta, Ryan M. Lau, Deepashri Thatte, Julien H. Girard, Ismael García-Bernete, Matthew J. Hankins

Faculty Publications

The dusty and molecular torus is an elusive structure surrounding supermassive black holes, yet its importance is unequivocal for understanding feedback and accretion mechanisms. The torus and accretion disk feed the inspiraling gas onto the active nucleus, launching outflows that fundamentally connect the active nucleus’s activity to the host galaxy. In this work, we utilize the aperture-masking interferometric mode onboard the JWST to achieve a resolution of 0.08" at 4.3 μm and bring out the fainter features in the central 10 pc of the Circinus galaxy. We show that most of the dust mass is located along the equatorial …

A Comparison Of Modeled Daytime E Regions From E-Probed And Pyiri With Ionosonde Observations, Daniel J. Emmons, Cornelius C. J. H. Salinas, Dong L. Wu, Nimalan Swarnalingam, Eugene V. Dao, Jorge L. Chau, Yosuke Yamazaki, Kyle E. Fitch, Victoriya V. Forsythe

Faculty Publications

While the F region is the primary focus of many ionospheric models because it contains the peak electron density, the E region is an important region for ionospheric conductivities and high-frequency radio propagation. This study analyzes modeled E regions from the newly developed PyIRI and E-PROBED models. A long-term comparison of E region predictions from E-PROBED and PyIRI with ionosonde observations is performed for three sites spanning low- (Fortaleza, Brazil), mid- (El Arenosillo, Spain), and high-latitudes (Gakona, Alaska). Modeled foE and hmE trends are compared against a combination of manually-scaled and automatically-scaled ionograms using ARTIST-5 for the period 2009–2024 for …

Antibacterial Peptides From Soybean (Glycine Max (L.) Merr.) With In Silico Study Against Escherichia Coli Bacteria, Dian Riana Ningsih, Ely Setiawan, Purwati Purwati, Zusfahair Zusfahair, Anita Hindayanti Rukmana

Karbala International Journal of Modern Science

Bioactive peptides are produced from soy milk protein hydrolysis using trypsin. The research began with the preparation and separation of soy milk protein, followed by fractionation using ammonium sulphate, protein hydrolysis, and SDS-PAGE analysis of protein hydrolysates. Fractions exhibiting the highest degree of hydrolysis were further fractionated by SPE and tested to determine the antibacterial activity Staphylococcus aureus and Escherichia coli. The peptide sequence of the active peptide as an antibacterial was identified, employing LC-HRMS. The mode of action between active peptides and bacterial membran was analysed using molecular dynamics (MD) simulation. The findings displayed that F15 contained the highest …

Measurement Of 18f(Alpha,P)21ne With The Array For Nuclear Astrophysics And Structure With Exotic Nuclei (Anasen), Keilah S. Davis

LSU Doctoral Dissertations

Certain (α,p) reactions on proton-rich nuclei are among the most important nuclear reactions occurring during Type I X-ray bursts, as well as being impactful in stellar explosions during the Asymptotic Giant Branch (AGB) phase and on accreting white dwarfs (WD). However, large uncertainties remain for reaction rates on some radioactive nuclei due to the lack of direct measurements. The Array for Nuclear Astrophysics and Structure with Exotic Nuclei (ANASEN) is a gas target and charged-particle detector designed for direct measurements of (α,p) reactions. ANASEN was redesigned with two hexagonal barrels of 100-µm-thick silicon strip surrounding the beam axis over a …

Sperm-Associated Antigen 6 (Spag6) As A Potential Marker Of Sperm Function In Diagnosing Male Infertility, Ibtisam A. Al-Ali,, Kawkab A. Alsaadi

Karbala International Journal of Modern Science

Background: While male infertility has become a significant global health concern, conventional analysis of semen has not made progress in the detection of contraindicated molecular biomarkers, such as sperm-associated antigen 6 (SPAG6), which is a protein involved in axonemal structure and flagellar motility.

Hypothesis: Expression of SPAG6 correlates with sperm motility and structural integrity. This means that its dysregulation may serve as a molecular indicator of impaired sperm performance.

Methods: A comprehensive review of recent studies was conducted with a focus on SPAG6’s molecular characteristics, expression patterns in normal versus abnormal spermatozoa, and the role it plays in motility-related …

Optimized Co2 Gas Sensing With Sns:Sm2o3/N-Si Nanocomposites Fabricated Via Spray Pyrolysis, Wasan A. Khalaf, Mays A. Hammadi, Mohammed J. Alsultani, Yahya R. Hathal, Mohammed O. Salman

Karbala International Journal of Modern Science

In this work, tin sulfide:samarium oxide (SnS:Sm₂O₃) composite films were deposited using a spray pyrolysis technique for room-temperature CO₂ gas sensing. X-ray diffraction (XRD) confirmed a polycrystalline SnS nature of orthorhombic-phase crystallinity at 10 at.% Sm ions, while 20 at.% Sm induced Sm₂O₃ as a separate phase. Field emission-scanning electron microscopy (FE-SEM) induced uniform grains and increased the surface roughness, enhancing gas adsorption. UV-visible absorbance revealed band-gap narrowing. Fourier transform infrared spectroscopy (FTIR) analysis revealed vibrational band shifts, confirming the structural modifications. Gas-sensing measurements demonstrated 5.72%, 19.65%, and 9.65% for pure SnS, …

Rogue Waves In Extended Gross-Pitaevskii Models With A Lee-Huang-Yang Correction, Sathyanarayanan Chandramouli, S. I. Mistakidis, G. C. Katsimiga, D. J. Ratliff, D. J. Frantzeskakis, P. G. Kevrekidis

Physics Faculty Research & Creative Works

We explore the existence and dynamical generation of rogue waves (RWs) within a one-dimensional quantum droplet-bearing environment. RWs are computed by deploying a space-time fixed point scheme to the relevant extended Gross-Pitaevskii equation (eGPE). Parametric regions where the ensuing RWs are different from their counterparts in the nonlinear Schrödinger equation are identified. To corroborate the controllable generation—relevant to ultracold atom experiments—of these rogue patterns, we exploit two different protocols. The first is based on interfering dam break flows emanating from Riemann initial conditions, and the second refers to the gradient catastrophe of a spatially localized waveform. A multitude of possible …

Haze Processing Of Atmospheric Particles During Wintertime In The Indo-Gangetic Plains, Susan Mathai, Amna Ijaz, Tania Gautam, Zezhen Cheng, Nurun Nahar Lata, Harsh Bhotika, David Tseng, Rosalie K. Chu, Lynn Mazzoleni, Claudio Mazzoleni, Swarup China

Michigan Tech Publications

The impacts of haze on visibility, air quality, and climate are not well quantified due to a lack of understanding of the evolution of the mixing state and phase state of atmospheric particles during haze processing. The variability of the mixing state of atmospheric particles contributes significantly to uncertainties associated with the estimated aerosol radiative forcing. We collected particle samples in January 2018 from the highly polluted Indo-Gangetic plain during hazy conditions to study haze-processed particles. Single particle analysis using multi-modal micro-spectroscopy techniques revealed an abundance (40–70% by number) of potassium-rich sulfate particles from biomass-burning influenced smoke. Tilted view imaging …

Thermal Performance And Specific Energy Consumption Of Traditional Tobacco Curing Barns In Tanzania, Seuri S. Kilakoi, Baraka Kichonge, Thomas Kivevele, Mtaki T. Maagi, Jacob B. Lisuma

Tanzania Journal of Science

Traditional tobacco curing barns remain the dominant technology in Tanzania due to their low construction cost and accessibility, particularly in major producing regions such as Tabora. However, their thermal inefficiency results in excessive firewood use and environmental degradation. This study presents a field-based performance evaluation of a traditional flue-curing barn at the Tobacco Research Institute of Tanzania. Environmental parameters and fuel consumption were monitored at 15- minute intervals throughout the yellowing, leaf drying, and stem drying stages. The curing process handled 429 kg of fresh tobacco using 1,016 kg of firewood, equivalent to 16,256 MJ of energy input. The specific …

Enhanced Superconductivity And Vortex Dynamics In Quasi-1d Tas2 Nanowires, Mathew Pollard, Visakha Ho, Clarissa Wisner, Eric W. Bohannan, Yew San Hor

Chemistry Faculty Research & Creative Works

We report the synthesis of high-quality 2H-TaS₂ nanowires via a controlled two-step conversion process from TaS₃ precursors, achieving robust superconductivity with a transition temperature T c ≈ 3.6K, which is significantly higher than bulk 2H-TaS₂ (T c ≈ 0.8K). Structural and compositional analyses confirm phase purity and preserved one-dimensional morphology, while magneto transport measurements reveal an enhanced upper critical field μ 0 H c2 (2K)≈5 T, far exceeding the bulk value (_μ0H_c2 (0)≈1.17T), attributed to dimensional confinement and suppression of charge-density wave order. Magnetic characterization demonstrates complex vortex dynamics, including flux jumps and a …

Statistics Of Glinting Clouds Observed By Dscovr And Geostationary Satellites, Tamás Várnai, Alexander Marshak, Alexander Kostinski

Michigan Tech Publications

This study examines how frequently the specular reflection of sunlight—that is, sun glint—reveals the presence of ice crystals that maintain a steady horizontal orientation. The study analyzes data from the Earth Polychromatic Imaging Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) spacecraft and from collocated images taken by geostationary satellites. The analysis of spatio-temporal variations in glint frequency over vegetated land surfaces reveals that (a) year-to-year variations are modest with no clear trends; (b) glints typically occur 7%–8% more frequently than previously estimated; (c) glints are most frequently observed during the May-August period, and over Asia. The results also …

Simulation Of Quantum Walks For Secure Data Access Patterns, Arslan Ahmad Janjua

Theses and Dissertations

Quantum computing is revolutionizing computational science, offering fundamentally new approaches to information processing that surpass classical limitations. One of the most versatile and powerful tools in this emerging field is quantum walks. Quantum walks are quantum analogs of classical random walks that leverage superposition and interference to explore complex spaces efficiently.

This thesis will explore how discrete-time scattering quantum walks can be simulated and analyzed to investigate patterns of secure data access. By modeling quantum walks on a variety of graph structures and studying the dynamics of marked vertices, the project aims to demonstrate how quantum interference and graph topology …

Crystal Structure Of Methanococcus Jannaschii Dihydroorotase With Substrate Bound, Jacqueline Vitali, Jay C. Nix, Haley E. Newman, Michael J. Colaneri

Physics Faculty Publications

Here, we report the X-ray structural analysis of dihydroorotase from Methanococcus jannaschii co-crystallized with dihydroorotate at pH 6.5. The crystals are isomorphous with the crystals of the apoenzyme, with space group P3₂21 and unit-cell dimensions a = b = 111.4, c = 101.2 Å. The structure was refined to R = 0.169 and R_free = 0.186 at a resolution of 1.87 Å at room temperature. During crystallization the degradative reaction took place, and the electron density in the active site corresponds to the substrate carbamoyl aspartate. Carbamoyl aspartate interacts with the protein in the active site …

Reflection Hoes Recorded On Photopolymerisable Glass Layers: A Step Towards Holographic Mirrors For Ar Technologies, David Ma, Suzanne Martin, Mohamed Oubaha, Tatsiana Mikulchyk

Conference Papers

Reflection Holographic Optical Elements (HOEs) offer a great potential for Augmented Reality (AR) display technologies due to their unique capability to redirect light with the predetermined wavelength in the opposite direction to the reconstructing light. AR displays based on HOEs enable a large variety of potential applications which necessitates the development of HOEs with long-term stable performance in challenging ambient conditions. Here, we present a study of the holographic recording capability of a photopolymerizable hybrid sol-gel (PHSG) which has shown to be a robust and water/temperature resistant material. Using optimal recording conditions, diffraction efficiency up to 18% has been achieved …

Parameter-Free Determination Of Au Nanorod Dimensions Using Depolarized Dls And Genetic Optimization, Nehal Nupnar, Geofrey Nyabere, Claire M.B. Bolding, Kiril A. Streletzky, Michael J.A. Hore

Physics Faculty Publications

Gold nanorods (AuNRs) have received considerable attention for their distinctive optical properties and well-defined, low-polydispersity dimensions. These characteristics position them as promising candidates for diverse applications in imaging, sensing, and treating diseases. However, accurate characterization of AuNRs in their native solution state, which is crucial to many applications, presents many challenges─especially if AuNRs are coated with surface layers (e.g., surfactants or grafted polymers). When applied to AuNRs with functionalized surfaces, common techniques such as transmission electron microscopy (TEM), small-angle scattering, and dynamic light scattering (DLS) can present limitations such as small sample sizes, the inability to detect light elements, a …

Temperature-Dependent Optical Properties Characterization Of Thermophotovoltaic Selective Emitter (4h– Sic, Aln Ceramic, And Aln/Al2o3), Po-Chao Huang

Honors Theses

Thermophotovoltaic (TPV) systems convert thermal radiation into electricity, and their efficiency depends strongly on the temperature-dependent optical response of the emitter materials. To support the design of high-temperature selective emitters, we characterized the thermo-optical properties of aluminum nitride ceramic (AlN), silicon carbide (4H– SiC), and aluminum oxide on aluminum nitride (AlN/Al2O3) thin film/substrate pairs, as a promising example of a bilayer emitter. Spectroscopic ellipsometry measurements from 240 nm to 2500 nm were performed while heating samples from room temperature to 600 °C. Using general oscillators modeling, we established accurate temperature dependent optical models consistent with literature values. Increasing temperature revealed …

Leveraging Machine Learning Techniques To Identify Catastrophic Outliers In Photometric Redshift Estimates, Jason Yoo

Honors Theses

Leveraging the unprecedented data volumes from modern astronomical surveys, this work addresses the critical challenge of identifying catastrophic outliers (COs) in photometric redshift (photo-z) estimates. Reliable redshift estimation is essential for precision cosmology, yet COs (galaxies with severely erroneous photo-z) can introduce significant systematic bias. We develop and evaluate two machine learning approaches for robust CO identification: a multilayer perceptron (MLP) utilizing photo-z point estimates and probability distributions, and a convolutional neural network (CNN) leveraging raw 5-band photometric images. Using datasets emulating LSST conditions, we demonstrate that the MLP model achieves high accuracy and stability across redshift bins, correctly identifying …

A Comparison Of Time-Dependent Cloudy Astrophysical Code Simulations With Experimental X-Ray Spectra From Kev Laser-Generated Argon Plasmas, N. Rathee, F. P. Keenan, R. J. R. Williams, Gary Ferland, S. J. Rose, S. White, D. Riley

Physics and Astronomy Faculty Publications

We have generated strongly photoionized Ar plasmas in experiments designed to use primarily X-ray l-shell line emission generated from Ag foils irradiated by the VULCAN high-power laser at the UK Central Laser Facility. The principle of the experiment is that use of line emission rather than the usual sub-keV quasi-blackbody source allows keV radiation to play a more dominant role compared to softer X-rays and thus mimic the effect of a blackbody with a higher effective spectral temperature. Our aim is to reproduce in the laboratory the extreme photoionization conditions found in accretion-powered astrophysical sources. In this paper, we compare …

Evaluation Of Commercial Li-Ion 2032 Coin Cells For Non-Ambient Temperature Applications, Shintaro Inaba , '26, Aaron Dubois , '26, Alex Wuttig , '26, S. Ji, Eric Novak, Hillary L. Smith

Physics & Astronomy Faculty Works

Rechargeable Li-ion 2032 coin cells are widely used in consumer electronics and fundamental battery research, yet their behavior under non-ambient conditions remains insufficiently characterized. In this work, five commercial LIR2032-type cells, including standard and high-capacity variants from multiple manufacturers, were evaluated over 100 galvanostatic cycles at 0 °C, 24 °C, and 60 °C. Ex situ X-ray diffraction confirmed graphite anodes and LiCoO₂ cathodes for all cells. Galvanostatic cycling revealed that room-temperature operation provides the most stable performance, while low-temperature cycling limits accessible capacity through kinetic constraints and high-temperature cycling accelerates degradation despite enhanced initial utilization. Differential capacity (dQ/dV) analysis identified …

Magnetic Anisotropy Engineering In Rare-Earth-Free Iron-Based Magnetic Materials, Pramanand Joshi

Physics Dissertations - Archive

The development of high-performance, rare-earth-free hard magnetic materials is critical for next-generation energy, information, and spin-based technologies. This dissertation investigates structure-property relationships in iron-based magnetic systems, including iron carbides, Fe-Co-B boride alloys, hexaferrites, and FeCo nanostructures, synthesized via chemical and metallurgical routes. Through controlled synthesis and comprehensive structural and magnetic characterization, this work demonstrates that magnetic anisotropy, coercivity, and thermal stability can be systematically controlled through morphology design, compositional tuning, microstructural refinement, and interparticle interaction modulation.

Morphology-driven enhancement of magnetic properties, particularly coercivity and blocking temperature, is established in phase-pure Fe₅C₂ nanostructures. By precisely controlling particle geometry, …

Applications Of Doppler Broadening Spectroscopy For The Characterization Of The Surface And Near Surface Of Two-Dimensional Heterostructures, Hany M. Mahdy

Physics Dissertations

This dissertation describes experiments and the analysis of Doppler broadening spectroscopy applied to metal surfaces (Cu, Ag, Au), graphene/Cu heterostructures, and SiGe heterostructures, with particular emphasis on the development of new approaches for extracting quantitative information from annihilation spectra.

The first part establishes the capability of Doppler broadening spectroscopy, particularly coincidence Doppler broadening (CDB), as a surface-sensitive technique. Measurements on clean and adsorbate-covered Cu, Ag, and Au surfaces demonstrate that Doppler-broadened annihilation spectra retain element-specific signatures from the topmost atomic layer. New analysis methods based on ratio-curve modeling enable identification and quantification of sub-monolayer adsorbates, including sulfur, oxygen, selenium, and …

Twisted Electron Collisions Enhance The Production Of Circular Rydberg States, H. S. Parker, S. L. Sims, D. J. Lamphere, Allison L. Harris

Faculty publications – Physics

Circular Rydberg states offer advantages for quantum information and quantum simulation platforms due to their long lifetimes and strong dipole–dipole interactions. Unfortunately, current techniques for the production of these states remain technically challenging. Here we investigate the ability of twisted electron collisions to produce circular Rydberg states. Twisted electrons carry quantized orbital angular momentum (OAM) that can be transferred to the electronic state of the atom, potentially providing an efficient means to generate circular Rydberg states. Using a fully quantum mechanical framework, we compute total excitation cross sections for circular Rydberg states of hydrogen, lithium, rubidium, and cesium targets using …

Accelerator Based Fusion Reactor With Magnetic Mirror, Keh-Fei Liu

Physics and Astronomy Faculty Publications

We consider an implementation of the novel accelerator-based fusion reactor scheme using a setup in which ion and electron beams are injected into the end openings of an axisymmetric magnetic mirror. While the magnetic mirror ensures transverse confinement of the plasma, the injected beams contribute to axial confinement, thereby extending the overall plasma lifetime. The ion beam energy is initially set above the resonance region of the fusion reactions, allowing fusion to occur both via resonance and thermal mechanisms as the beam slows down to the plasma temperature. Beam energy loss (stopping power) contributes to plasma heating, offsetting radiative losses …

Dynamical Phases Of Higher Dimensional Floquet Cfts, Diptarka Das, Sumit R. Das, Arnab Kundu, Krishnendu Sengupta

Physics and Astronomy Faculty Publications

This paper investigates the dynamical phases of Floquet Conformal Field Theories (CFTs) in space-time dimensions greater than two. Building upon our previous work which introduced quaternionic representations for studying Floquet dynamics in higher-dimensional CFTs, we now explore more general square pulse drive protocols that go beyond a single SU(1,1) subgroup. We demonstrate that, for multi-step drive protocols, the system exhibits distinct dynamical phases characterized by the nature of the eigenvalues of the quaternionic matrix representing time evolution in a single cycle, leading to different stroboscopic responses. Our analysis establishes a fundamental geometric interpretation where these dynamical phases directly correspond to …

Emission-Line Diagnostics At Z ≳ 2: A Probe Of The Ionizing Spectrum And Α-Enhancement Beyond Cosmic Noon, Leonardo Clarke, Natalie Lam, Alice E. Shapley, Michael W. Topping, Gabriel B. Brammer, Ryan L. Sanders, Naveen Reddy, Shreya Karthikeyan

Physics and Astronomy Faculty Publications

We analyze several key rest-optical emission-line ratios in a sample of 828 galaxies as well as composite spectra from JADES DR3 in the range 1.4 <  z <  7. These emission-line ratios include: [O iii]λ5008/Hβ, [N ii]λ6585/Hα, [S ii]λλ6718, 6733/Hα, [O i]λ6302/Hα, O32, R23, Ne3O2, and RO2Ne3. We find evidence for a harder ionizing spectrum at z ∼ 3.5 compared to z ∼ 2 at fixed gas-phase metallicity, resulting in a pronounced shift in the star-forming galaxy locus on the [N ii]/Hα Baldwin-Phillips-Terlevich (BPT) diagram and the O32 versus R23 diagram. At …