Astrophysics and Astronomy Commons^™

Challenging $\Lambda$Cdm: Unraveling Cosmic Distances, Dark Sector Phenomenology, And Alternative Primordial B-Mode Sources, Kylar L. Greene

Physics & Astronomy ETDs

The dominant Lambda Cold Dark Matter (LCDM) cosmological model, while remarkably successful, increasingly shows signs that it may not fully describe our Universe, as persistent tensions in expansion rates and structure formation remain unresolved. In this thesis, I challenge the LCDM paradigm using novel theoretical frameworks combined with rigorous numerical analyses. I demonstrate that the expansion-rate tension fundamentally reflects underlying distance disagreements, and that the Thomson scattering rate strongly restricts higher pre-recombination expansion rates without additional physics. Further, I present a novel cosmological model using a mirror dark sector and varying fundamental constants, revealing an observational degeneracy allowing significantly higher …

Cross-Correlation Studies Of The Cosmological 21 Cm Signal And High-Redshift Galaxy Distributions, Simon Matin

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Epoch of Reionization (EoR) marks a critical phase in cosmic history, during which time the first stars and galaxies ionized the surrounding neutral hydrogen gas. A powerful way to probe this period is by cross-correlating the 21 cm signal from neutral hydrogen with high-redshift galaxy distributions. In this study, we analyze the 21 cm-galaxy cross-power spectrum using simulated sky maps and explore its redshift evolution, revealing a transition from positive correlation at early times (high redshift) to anti-correlation at later stages of reionization (low redshift). Our results highlight the sensitivity of the cross-power spectrum to the evolving ionized structure …

On Efficient Position Dependent Computation Of Radiation Near Accretion Disks, Kara Jeanette Smith

UNLV Theses, Dissertations, Professional Papers, and Capstones

Accretion onto super massive black holes (SMBH) plays a vital role in explaining our observations of active galactic nuclei (AGN). One key aspect of observations of AGN is the prevalence of massive outflows which transport matter and energy away from the galactic core. These outflows are characterized by highly blueshifted absorption lines as radiation from the accretion disk is absorbed by gas which is moving toward us. Radiation pressure on spectral lines is expected to play a vital role in launching and accelerating these winds. At the other end of the spectrum of black hole masses, accretion disks in X-ray …

Quasi-Normal Modes Of Extended Uncertainty Principle Kerr Black Holes, Ava Hoeger, Jonas Mureika

Honors Thesis

The current understanding of gravity is shaped largely by Albert Einstein’s theory of General Relativity. This theory is highly successful at predicting phenomenon on macroscopic scales, but it faces unphysical singularities at quantum scales. This thesis will explore the possibility of combining General Relativity with quantum mechanics through the Extended Uncertainty Principle (EUP), which provides a new, fundamental length scale correction to the Heisenberg Uncertainty Principle. This allows for quantum gravity effects at macroscopic scales, which will be examined through Kerr black holes with event horizons on the order of . These black holes are rotating and electrically neutral, and …

Mass Transfer In Binary Stars, Pierson Lipschultz

COD Library Student Research and Award Symposium

I investigated the properties of mass transfer in binary star systems. I feature results from Vela X-1, V404 Cygni, and W Ursae Majoris as well as corroborating data from POSYDON. Furthermore, I found the local populations on an HR diagram of each system. Additionally, I found anomalous data properties in both MESA and V404 Cygni which warrant further investigation.

Faculty Sponsor: Professor Joseph DalSanto

In Search Of Extreme Extragalactic Energy: A Catalog Of Tev-Emitting Bl Lac Candidates From Erosita And Wise, Cassidy M. Metzger, Manel Errando, Andrea Gokus

Senior Honors Papers / Undergraduate Theses

Active galactic nuclei (AGN) are supermassive black holes that reside at galactic centers and are actively accreting matter. In approximately 10% of cases, AGN produce relativistic jets: collimated streams of particles that travel for thousands of light years and have been detected at TeV energies by ground-based gamma-ray observatories. However, the mechanisms that accelerate particles beyond the TeV scale are largely unknown. Currently, only 56 objects are confirmed to accelerate particles to these extreme energies. Here we provide a selection of over 150 sources that exhibit infrared (IR) and X-ray emission profiles similar to those of the 56 TeV sources. …

Observational Properties Of Near-Maximal Spin Black Holes With The Eht, Tegan A. Thomas, Angelo Ricarte, Yajie Yuan

Senior Honors Papers / Undergraduate Theses

In 2021 and 2024, the Event Horizon Telescope (EHT) collaboration published the first polarized images of the supermassive black holes (SMBHs) M87* and Sgr A*, which allowed us to place important constraints on the accretion flow and underlying space-time. Of particular interest is the dimensionless spin parameter "a_•", which theoretically may attain a maximum value of a_• = 0.998 when spun up by a thin accretion disk. On the other hand, mechanisms including incoherent accretion, SMBH mergers, and spin extraction via jets, are hypothesized to spin down SMBHs from these near-extremal values. In this work, we perform …

Tidal Heating In Gas Giant Ice Moons, Sage Benz-Narveson

Senior Seminars and Capstones

This presentation is on the icy moons of Jupiter and Saturn, Europa and Enceladus. They are both known for being relatively large moons of gas giants made of a lot of water ice with silicate cores. Both are also suspected to harbor liquid oceans underneath their icy surfaces, sustained by salinity and tidal heating. Liquid water is of extreme interest to astrobiologists, which this paper will address, but it is primarily about tidal heating and its implications for the size of the subsurface oceans.

Transmutation, Sam Berger

MFA in Visual Art

My artistic practice is about change itself. I am inspired by the doubling and layering effects that came out of Surrealist Photography. Scale, fracture, and doubling are intentional components of my process. I combine those methods to create complex works of art, focusing on the untamable light that I hope to capture when making my images, which often are self portraits. Poetry is an integral element of this thesis text as well as my art making process. Through my poetic work I hope to offer my audience a glimpse into how I see and experience the world. This thesis text …

Investigating The Parameters Driving Black Hole-Galaxy Co-Evolution, Rachel Cleveland

University Scholar Projects

In this research project, we study supermassive black holes that reside in the center of galaxies. More specifically, we explore the self-regulatory nature of these black holes as well as their relationship with their host galaxies. Simulations are utilized to study these cosmic entities, as they allow us to investigate the implications of different physical mechanisms in galaxy evolution. We use Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) to identify the astrophysical parameters that drive the black hole-galaxy coevolution. Building on our earlier results based on the SIMBA simulation, which established broad correlations with black hole and stellar mass, …

The Search For Slow Particles And Magnetic Monopoles With Nova, John Clark

Poster Presentations

Singular magnetic poles, north or south, have been theorized to exist for hundreds of years. In the modern day, the elusive singular magnetic pole still remains undiscovered. The appearance of this particle would help confirm many Grand Unified Theories, GUTs, and revolutionize our understanding of some of the fundamental forces of the universe. Fermilab's NOvA collaboration is working on ways to screen and detect magnetic monopoles and other slow-moving particles coming from outer space alongside their main mission to study neutrinos. The aim of this work is to determine and improve the Far Detector’s efficiency at identifying slow moving particles. …

Simulations Of Magnetar Spin-Down Lifetimes Using Magnetic Braking Models, Sophie Wessel

Honors College Theses

The beginnings of magnetar lifetimes are not very well understood. It is important to improve our understanding of magnetar origins in order to investigate possible evolutionary connections to other classes of NS, such as X-ray dim isolated NSs (XDINSs). Here we follow in the steps of another paper1 in modeling the spin evolution of magnetars, utilizing two avenues of evolution: one involving exponential B-field decay, and the other involving suband super-exponential B-field decay. We replicate the results of the paper, utilizing Monte Carlo methods to generate and evolve synthetic populations of magnetars, which are then compared to the current known …

From The University To The Universe: Byu’S West Mountain Observatory, Amber Zendejas, Dan Broadbent

BYU West Mountain Observatory Project

Brigham Young University’s West Mountain Observatory (WMO) is a research facility that offers primarily undergraduate students valuable mentoring and hands-on learning opportunities. Established in 1981, the observatory was built in response to increasing light pollution in Provo, Utah, which began affecting research at the Orson Pratt Observatory (OPO) atop the Eyring Science Center on the BYU main campus. Before WMO was created, OPO served as the primary observatory for astronomical research at BYU. Construction plans for a new observatory began in the late 1970s, as university planners and astronomers sought a location with minimal light pollution, favorable elevation, relatively easy …

Hα Variability Of Ab Aur B With The Hubble Space Telescope: Probing The Nature Of A Protoplanet Candidate With Accretion Light Echoes, Brendan P. Bowler, Yifan Zhou, Lauren I. Biddle, Lillian Yushu Jiang, Jaehan Bae, Laird M. Close, Katherine B. Follette, Kyle Franson, Adam L. Kraus, Aniket Sanghi, Quang Tran, Kimberly Ward-Duong, Ya Lin Wu, Zhaohuan Zhu

Astronomy: Faculty Publications

Giant planets generate accretion luminosity as they form. Much of this energy is radiated in strong Hα line emission, which has motivated direct imaging surveys at optical wavelengths to search for accreting protoplanets. However, compact disk structures can mimic accreting planets by scattering emission from the host star. This can complicate the interpretation of Hα point sources, especially if the host star itself is accreting. We describe an approach to distinguish accreting protoplanets from scattered-light disk features using “accretion light echoes.” This method relies on variable Hα emission from a stochastically accreting host star to search for a delayed brightness …

Effects Of The Gravity Gradient On The Path Of 1i/‘Oumuamua, Hannah R. Richardson

Poster Presentations

In October 2017, the asteroid 1I/’Oumuamua first passed into viewing range [1]. The asteroid is notable for being the first interstellar object to enter the solar system. 1I/’Oumuamua was also unusual in its geometry; it is thought to have an aspect ratio of 6:1 and a length of approximately 400 m [2] [3]. The asteroid was observed to experience a non-Keplerian acceleration estimated to be on the order of 1×10−6 m s-2 Several theories have been proposed for the cause of this acceleration, all of which are non-gravitational in nature: volatile outgassing, photon pressure, and solar winds [1][4]. However, none …

Jwst Reveals The Diversity Of Nuclear Obscuring Dust In Nearby Agn: Nuclear Isolation Of Miri/Mrs Data Cubes And Continuum Spectral Fitting, Omaira González-Martín, Daniel J. Díaz-González, Mariela Martínez-Paredes, Almudena Alonso-Herrero, Enrique López-Rodríguez, Begoña García-Lorenzo, Cristina Ramos Almeida, Ismael García-Bernete, Donaji Esparza-Arredondo, Sebastian F. Hoenig, Santiago García-Burillo, Chris Packham, Nancy A. Levenson, Alvaro Labiano, Miguel Pereira-Santaella, Francoise Combes, Anelise Audibert, Erin K.S. Hicks, Lulu Zhang, Enrica Bellocchi, Richard I. Davies, Laura Hermosa Muñoz, Masatoshi Imanishi, Claudio Ricci, Marko Stalevski

Faculty Publications

We investigate the capabilities of the mid-infrared instrument (MIRI) of JWST to advance our knowledge of active galactic nucleus (AGN) dust using the spectral fitting technique on an AGN collection of 21 nearby (z < 0.05) AGN (7 type-1 and 14 type-2) observations obtained with the medium resolution spectroscopy (MRS) mode. This collection includes publicly available AGN and data from the collaboration of Galactic Activity, Torus, and Outflow Survey (GATOS). We developed a tool named MRSPSFisol that decomposes MRS cubes into point-like and extended contributions. We found statistically good fits for 12 targets with current AGN dust models. The model that provides good fits (χ²/dof< 2) for these 12 targets assumes a combination of clumpy and smooth distribution of dust in a flare-disc geometry where the dust grain size is a free parameter. Still, two and one AGN statistically prefer the disc + wind and the classical clumpy torus model, respectively. However, the currently available models fail to reproduce 40 per cent of the targets, likely due to the extreme silicate features not well reproduced by the models and signatures of water-ice and aliphatic hydrocarbon absorption features in most targets. New models exploring, for instance, new chemistry, are needed to explain the complexity of AGN dust continuum emission observed by JWST.

Effects Of The Gravity Gradient On The Path Of 1i/‘Oumuamua, Hannah R. Richardson

Honors Theses

In October 2017, the asteroid 1I/’Oumuamua first passed into viewing range [1]. The asteroid is notable for being the first interstellar object to enter the solar system. 1I/’Oumuamua was also unusual in its geometry; it is thought to have an aspect ratio of 6:1 and a length of approximately 400 m [2] [3]. The asteroid was observed to experience a non-Keplerian acceleration estimated to be on the order of 1⇥10−6 m s2 . Several theories have been proposed for the cause of this acceleration, all of which are non-gravitational in nature: volatile outgassing, photon pressure, and solar winds [1][4]. However, …

The Search For Slow Particles And Magnetic Monopoles With Nova, John Clark

Honors Theses

Singular magnetic poles, north or south, have been theorized to exist for hundreds of years. In the modern day, the elusive singular magnetic pole still remains undiscovered. The appearance of this particle would help confirm many Grand Unified Theories, GUTs, and revolutionize our understanding of some of the fundamental forces of the universe. Fermilab's NOvA collaboration is working on ways to screen and detect magnetic monopoles and other slow-moving particles coming from outer space alongside their main mission to study neutrinos. The aim of this work is to determine and improve the Far Detector’s efficiency at identifying slow moving particles. …

An Integrative Approach To Einstein’S Field Equations Of General Relativity For High School Students, Christina M. Aintablian

Senior Honors Theses

Einstein’s Field Equations form the foundation of the theory of General Relativity, describing the interdependence of mass-energy and spacetime curvature, where curvature gives rise to gravity. However, the complexity of these equations makes them difficult for high school students to grasp. The mathematical framework of General Relativity is introduced step by step, beginning with relative motion and culminating in a discussion of complex phenomena that challenge modern physics. Each explanation intertwines core concepts of relativity with pre-established mental models to enhance learning. Through the use of figures, analogies, narratives, and thought experiments, a structured framework is developed to make relativity …

A Spectroscopic Survey Of Atmospheres Of Super-Earths, Luke Brust

Honors Theses

Recent research has made it possible to use spectroscopy to analyze the composition of the atmospheres of exoplanets, planets that orbit other stars. Most projects thus far have focused on the atmospheres of gas giants, as it is less challenging to observe them with available equipment. This project studies the atmospheres of four Super- Earths, planets that have a mass greater than the Earth but smaller than Neptune. This is accomplished by processing the raw spectroscopic data from the Hubble Space Telescope and modeling the atmosphere using the program 𝝉-Rex3. This survey found clear results from two of the selected …

Impact Of Magnetic Fields On Cosmic Ray Density In Molecular Clouds, Byron Jesus Encinas Velazquez

Open Access Theses & Dissertations

We investigate the effects caused by Cosmic Rays (CRs) in a Molecular Clouds (MCs) environment and the effects of varied magnetic field configurations in the core (r = 1 Pc ) of a MC. We take as initial conditions for the interstellar medium a product of various supernova explosions as injected initial perturbation and observe the evolution during the timescale of ~4.5 Myrs. We compute the CR reduction factor R as a measure of the density of a distribution of particles traveling with a guiding center along randomized field lines near the core and discuss their impact on the ionization …

Probing The 'Mev Gap': Discovery And Characterization Of Persistent And Transient Mev-Gev Gamma-Ray Sources With The Fermi Large Area Telescoope, Scott Joffre

All Dissertations

The MeV Gap is a moniker for the energy regime E~0.1-100 MeV that has lacked sensitive observations for the last 20 years. This is not out of scientific disinterest, but observational challenges. The only instrument currently available to make observations in the MeV Gap is the Fermi Large Area Telescope (LAT). For the first time ever, Fermi-LAT has been leveraged to push its observational capabilities to its absolute lower energy limit to end this 20-year observational gap. Observing the MeV sky is imperative for identifying some of the most luminous galaxies in the Universe known as blazars. The brightest blazars …

The Effect Of Nuclear Isomers On S-Process Nucleosynthesis, Jaad Tannous

All Dissertations

s-Process nucleosynthesis is a process in which stars produce elements of mass range A = 57 to 210. Since the days of B2FH, immense work has gone into quantifying and computing s-process yields and pathways. We expand upon said work along two fronts. The first front sets up the framework for proper treatment of nuclear isomers in network calculations. We apply the framework to study 85Kr, which is a pivotal isotope in the s-process chain that affects the abundance yields of Strontium and Rubidium isotopes. In particular, we are interested in the ratio of 88Sr/86Sr and 87Rb which are important …

Constraining Neutron Star Kicks Through Gravitational Wave Detection, James Phillips

Graduate Theses and Dissertations

Neutron stars have, on average, much higher proper motions than those of hot and bright O and B type main sequence stars. Thus, it is widely suspected that asymmetries in core-collapse supernovae provide a substantial kick to these compact objects at birth. Gen- eral Relativity predicts that such supernova asymmetries will generate bursts of gravitational radiation, though no such burst has been yet detected. Here we argue that the polarization amplitudes of those gravitational waves can be used to calculate the kicks imparted on that nascent neutron star. We begin by reviewing the evidence for natal kicks, then we describe …

Dissolving Sand Into Fog - Portraying Long Term Temporal Illusions Through Music, Kyle Bergler

Honors Projects

Long-term temporal illusions permeate our day-to-day lives, but due to their highly subjective nature, few are familiar with them. To help introduce these topics in a way that lets a wider audience connect individually with them, I composed three works for percussion ensembles, each in a different style, and each portraying one or multiple long-term temporal illusions. All of these pieces were composed and rehearsed throughout the spring 2025 semester and premiered at my senior recital on April 19, 2025.

Global Ionospheric F Region Parameters From Gnss-Pod Limb Measurements: Evaluations And Comparisons With Two Empirical Models - Iri-2020 And Nequick-2, Nimalan Swarnalingam, Dong L. Wu, Dieter Bilitza, Daniel J. Emmons, Cornelius Csar Jude H. Salinas, Artem Smirnov, Yenca Migoya-Oru

Faculty Publications

An optimal estimation (OE) technique has recently been developed for F region electron density (Ne) using Global Navigation Satellite System (GNSS) limb sounding on low Earth orbit (LEO) satellites (COSMIC-2, Spire, and FengYun-3). This method provides unprecedented spatiotemporal sampling for global monthly Ne climatology within 100–500 km in 2 hr intervals. The global dataset, collected during mid to moderately high solar activity, is compared with leading models: IRI-2020 and NeQuick-2. Diurnal variations in summer, winter, and equinoctial months are examined for the F2-layer peak, as well as the topside and bottomside of the F region. The observed and modeled NmF2 …

Extraterrestrial - Why They're Almost Certainly Out There, Marcus Brown

2025 Student Academic Showcase

This was an essay I did for my English Composition II class. It’s evaluating an argument from a TED talk of my choice. The TED talk I chose for this writing project was "Extraterrestrial’s - Why They’re Almost Certainly Out There” by Chris Crowe talking about the many exoplanets out there in our universe and beyond. The presentation explains the different sizes, the atmosphere, and the number of exoplanets capable of hosting life. The statistics were used in this analysis like the amount of hydrogen dioxide on each exoplanet. I had to determine if Chris Crowe did a good job …

There's A Method To This Physics Madness, Hanna J. Ross

Physics and Astronomy Presentations

Physics tends to be seen by the general public as scary and unattainable, especially for students who are non-STEM majors. However, at Ursinus College (as well as many other institutions) the professors employ the use of specific problem-solving strategy instruction to mitigate these fears and further general problem solving skills. This study reviews previous experiments evaluating the merit of this strategy and analyzes its results as it relates to Physics on Screen, a physics class at Ursinus geared specifically towards non-majors.

Rings Of Ice, Erik Johnson

Natural Science Faculty

Have you ever seen the Milky Way? For most Americans, it is impossible to see the band of light from the galaxy outside their homes. To be able to experience the night sky as our ancestors did, we have to travel to places away from light pollution. International Dark Sky Week, which is happening April 22–30 this year, celebrates the night sky and offers everyone a chance to reflect on the lighting choices made around their home and in their community.

Search For Continuous Gravitational Waves From Known Pulsars In The First Part Of The Fourth Ligo-Virgo-Kagra Observing Run, A. G. Abac, R. Abbott, I. Abouelfettouh, F. Acernese, Teviet Creighton, Mario C. Diaz, Francisco Llamas Villarreal, Soma Mukherjee, Volker Quetschke, Wenhui Wang

Physics & Astronomy Faculty Publications

Continuous gravitational waves (CWs) emission from neutron stars carries information about their internal structure and equation of state, and it can provide tests of general relativity. We present a search for CWs from a set of 45 known pulsars in the first part of the fourth LIGO–Virgo–KAGRA observing run, known as O4a. We conducted a targeted search for each pulsar using three independent analysis methods considering single-harmonic and dual-harmonic emission models. We find no evidence of a CW signal in O4a data for both models and set upper limits on the signal amplitude and on the ellipticity, which quantifies the …