Master of Science, Miami University, 0, Physics

In this thesis paper, we are going to discuss the galactic dynamics under the classical Newtonian model, MOND model, and MOND+EFE model. Because the effective range of gravity can reach infinity, the system of each DSPH galaxy will suffer from the external field effect. Under EFE, the dynamics of stars inside the DSPH galaxy will shift from MOND pattern to Newtonian pattern. So, in this thesis, we will compare dynamics of three DSPH galaxies under Newtonian, MOND, and MOND+EFE models. Moreover, I will compare the observational data from (Walker 2009) with simulated results. For the simulation, I will use the Plummer mass distribution model for the simulated DSPH galaxy. For computing the stellar dynamics inside the DSPH galaxy, we will use the Hermite Individual Time Step technique. For the Line of Sight dispersion, it is generated based on the statistics of simulated data. Comparing the simulated result with the observational result from (Walker 2009), we found that the observational result is a bit messy but it generally agrees with the MOND+EFE model if it is under correct mass-light ratio.

Doctor of Philosophy, The Ohio State University, 2024, Physics

Hawking radiation sets stringent constraints on Primordial Black Holes (PBHs) as a dark matter candidate in the M ~ 10 16 g regime based on the evaporation products such as photons, electrons, and positrons. This motivates the need for rigorous modeling of the Hawking emission spectrum. Using semi-classical arguments, Page [Phys. Rev. D 16, 2402 (1977)] showed that the emission of electrons and positrons is altered due to the black hole acquiring an equal and opposite charge to the emitted particle. The Poisson fluctuations of emitted particles cause the charge Z|e| to random walk, but since acquisition of charge increases the probability of the black hole emitting another charged particle of the same sign as the charge of the black hole, the walk is biased toward Z=0, and P(Z) approaches an equilibrium probability distribution with finite variance < Z2>. This thesis explores how this ``stochastic charge'' phenomenon arises from quantum electrodynamics (QED) on a Schwarzschild spacetime. We prove that (except for a small Fermi blocking term) the semi-classical variance < Z2> agrees with the variance of a quantum operator < 𝒵2>, where 𝒵 may be thought of as an ``atomic number'' that includes the black hole as well as charge near it (weighted by a factor of 2M/r). In QED, the fluctuations in < 𝒵2> do not arise from the black hole itself (whose charge remains fixed), but rather as a collective effect in the Hawking-emitted particles mediated by the long-range electromagnetic interaction. The rms charge < Z2> 1/2 asymptotes to 3.44 at small PBH masses M≲2x1016g, declining to 2.42 at M=5.2x1017g. Our construction also identifies which terms in the full QED Hamiltonian give rise to the stochastic charge effect, so that we can avoid ``double counting'' as we work toward a full calculation of the corrections to Hawking radiation at order O(α), where α ≈ 1/137 is the fine structure constant. As a secondary topic, we explore if resonances, q (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2024, Astronomy

Accretion onto a supermassive black hole (SMBH) is the most radiatively-efficient processes in the Universe, capable of producing more radiation in a region the size of the Solar System than is produced in an entire galaxy. When this happens, the system surrounding the SMBH is called an active galactic nucleus (AGN). AGNs have tremendous impact on star formation and the growth of galaxies as well as being unique probes of many important astrophysical processes. Indeed, understanding the growth of SMBHs and the AGNs that drive this growth is one of the highlighted topics in the 2020 Astronomy & Astrophysics Decadal Survey. AGNs are systems with multiple components, and the most important of these is the accretion disk surrounding the SMBH. The disk produces most of the luminosity as optical and UV thermal continuum emission. This emission is also stochastically and continuously time variable, and despite decades of study of this phenomenon, we still do not fully understand what drives the variability. In the first part of my thesis, I introduce a new method of understanding and analyzing this stochastic variability. By assuming an axisymmetric accretion disk with a radial temperature profile, I use well-sampled multi-band UV/optical lightcurves to create "maps" of the accretion disk resolved in time and radius. The maps for a majority of the AGNs modeled are dominated by temperature fluctuations that move radially inwards and outwards slowly (relative to the speed of light). These structures challenge the current paradigm where accretion disk variability is dominated by processes like reverberation, as reverberation produces fluctuations that only move outwards at the speed of light. I spend the next part of my dissertation addressing transient variability in AGNs and around quiescent SMBHs. These include: changing-look events, where an AGN changes from one "type" to another over timescales of months to years; tidal disruption events (TDEs), where (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2024, Physics

In the seconds following their formation in core-collapse supernovae, `proto'-neutron stars (PNSs) drive neutrino-heated magneto-centrifugal winds. The neutrino-driven wind phase during the cooling of the PNS lasts $\sim 1-100$\,s. We construct unprecedentedly realistic models of the PNS cooling phase using two-dimensional axisymmetric magnetohydrodynamic simulations. We include the effects of neutrino heating and cooling, employ a general equation of state, consider strong magnetic fields along with a dynamic PNS magnetosphere, and include the effects of PNS rotation. We show that relatively slowly rotating magnetars (strongly magnetized PNSs) with initial spin periods $P_{\star0} \gtrsim 100$\,ms spin down rapidly during the cooling epoch. For polar magnetic field strengths $B_0\gtrsim10^{15}$\,G, we show that the spindown timescale is of the order seconds in early phases. We show that magnetars with mass $M$ born with $B_0$ greater than $\simeq1.3\times10^{15}\,{\rm\,G}\,(P_{\star0}/{400\,\rm\,ms})^{-1.4}(M/1.4\,{\rm M}_\odot)^{2.2}$ spin down to periods $> 1$\,s in just the first few seconds of evolution. We discuss the implications for observed magnetars, including the discrepancy between their characteristic ages and supernova remnant ages. On the other hand, we show that rapidly rotating magnetars with initial spin periods $P_{\star 0}\lesssim 4$\,ms and $B_0\gtrsim 10^{15}$\,G can release $10^{50}-5\times 10^{51}$\,ergs of energy during the first $\sim2$\,s of the cooling phase. Based on this result, it is plausible that sustained energy injection by magnetars through the relativistic wind phase can power gamma-ray bursts (GRBs). We also show that magnetars with moderate field strengths of $B_0\lesssim 5\times 10^{14}$\,G do not release a large fraction of their rotational kinetic energy during the cooling phase and hence, are not likely to power GRBs. We hypothesize that moderate field strength magnetars can be central engines of superluminous supern (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2024, Physics

Self-interacting dark matter (SIDM) cosmologies admit an enormous diversity of dark matter (DM) halo density profiles, from low-density cores to high-density core-collapsed cusps. The possibility of the growth of high central density in low-mass halos, accelerated if halos are subhalos of larger systems, has intriguing consequences for small-scale observables such as substructure lensing, dwarf galaxies and stellar streams. However, following the evolution of low-mass subhalos in their host systems is computationally expensive, sometimes even prohibitive, with traditional N-body cosmological simulations. In this thesis work, we are thus motivated to develop a series of hybrid methods for simulations of low-mass subhalos, from core-creation to core-collapse (or complete dissolution in the host), also with the orbital effects from the host halo consistently captured. This thesis consists of three parts: in the first chapter, we detail our hybrid method tracing individual SIDM subhalos; in the second chapter, we use the hybrid method to simulate a realistic population of subhalos, also with a new hierarchical framework to further reduce the computational cost; in the third chapter, we populate individual SIDM subhalos with galaxies in the initial condition, and study the evolution of stellar properties in response to SIDM halo evolution and orbital effects.

Bachelor of Science (BS), Ohio University, 2024, Astrophysics

Through a collaboration with the Dark Energy Spectroscopic Instrument (DESI), this thesis utilizes the DESI N-body simulation mock galaxies to perform statistical analyses over the data. Through this analysis, best-fit cosmological parameters are determined. The processes followed within this thesis paper outline the typical DESI analysis process when performing parameter estimation.

Doctor of Philosophy, The Ohio State University, 2024, Physics

Stellar clusters form inside large clouds of gas, which collapse under gravity until the feedback from the newly formed stars begins to push the gas away, disrupting further star formation. In this dissertation we explore several of the feedback mechanisms responsible for stopping star formation. We will look in depth at two mechanisms in particular: Radiation pressure and cosmic ray diffusion. To analyze these pressures, we build simple models which we then expand. Radiation pressure's role depends greatly on the composition of the dust embedded in the gas the stars form from. The dust interacts with the photons from the star cluster, scattering and absorbing them, before re-radiating the photons in the infra-red. To build a more realistic model of radiation pressure, we use time dependent spectral data from simulations and realistic dust grain distributions and optical properties. The effects of cosmic ray diffusion are controlled by several parameters, such as the diffusion coefficient and the size scale of the shell of material the cosmic rays are acting on. We compare cosmic ray pressure to radiation pressure, and the pressure from hot ionized gas around the stellar cluster. We also apply our analysis of each of these pressures to observations. We do this to estimate the role of each pressure in observed regions, helping to explore the mechanisms which govern the star formation rates in star-forming regions of galaxies. Additionally, we analyze the dynamics of shells driven by radiation pressure, cosmic ray diffusion, and the pressure from hot ionized gas. From these simple dynamical models we draw conclusions about the roles of each of the pressures, and examine the parameter space where each dominates. We find that radiation pressure is highly important to the initial stages of feedback, dominating the other studied pressures for the youngest and most compact clusters. Radiation pressure can rapidly drive gas away from the central star cluster, (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2024, Astronomy

Planet formation is intrinsically linked to the star formation history and evolution of the Milky Way through elemental abundances and galactic locations. The environments in which a planet may form infuences their composition or whether a planet population may form at all. There are key stellar abundances that act as tracers for planet formation (e.g., Fe), constrain rocky planet composition (i.e., Fe, Mg, Si), and volatiles that impact the composition of magmas (i.e., H2O, CO2). Historically, spectroscopically-derived stellar abundances have been difcult to obtain for large stellar samples as they require long observations. However, spectroscopic surveys such as LAMOST (Luo et al. 2015) have been instrumental in obtaining stellar abundances. This dissertation uses stellar abundances to connect theoretical and observational studies of exoplanets. Specifcally, we constrain planet formation observationally using two stellar samples where Fe as a proxy for the available metals in the protoplanetary disk at the time of formation. The study of the frst stellar sample resulted in the frst observational study to search the galactic halo for planets placing the frst constraints on planet formation in the halo. With the second stellar sample, we constrained the occurrence rate of super-Earths (1-∼1.8 R⊕) as a function of metallicity ([Fe/H]). Our study challenged conventional theory that predicts that super-Earths had a weaker trend with metallicity with a sample ∼ 2 times larger than previous metal-poor stars, resulting in the frst evidence for a strong trend for super-Earth formation at low-metallicity regime. Considering super-Earth composition post-formation, rocky planets transition through a magma ocean phase where volatiles such as, H2O, CO2 may impact the properties of the magma (i.e., melting temperature, compressibility). To investigate the impact of volatiles on magma ocean planets, we chose to consider the impact of magma composition on the observable properties (open full item for complete abstract)

Master of Sciences, Case Western Reserve University, 2024, Physics

Ultra high-energy cosmic rays (UHECR) are cosmic rays with energies greater than 1~EeV. The Origin of UHECR has remained a mystery for decades. On Earth we detect UHECR indirectly due to extensive air showers. We use detection on the ground to reconstruct the arrival direction, energy, and composition of UHECR. Auger@TA is a collaboration between the two major observatories for UHECR: the Pierre Auger Observatory (Auger) and the Telescope Array (TA). The main goal for Auger@TA is to conduct an in-situ cross-calibration based on air showers detected using surface detectors from both projects: TA scintillator detectors vs.~Auger Water Cherenkov Detectors (WCD). Auger@TA (Phase 2) consists of a small array of Auger WCD surface detector stations deployed within the existing TA observatory near Delta, Utah. This allows for individual cosmic-ray air shower events to be simultaneously and independently detected and reconstructed by both Auger and TA surface detectors, providing for an event-by-event comparison. In this thesis, we will discuss laboratory experimental work on the fabrication and testing of the photomultiplier tube (PMT) base electronics to be used on each WCD surface detector. These PMT bases have been deployed into the field. We also describe an improved analysis method to calibrate the energy response of Auger@TA WCD using vertical through-going muons, which has been applied to data collected from Auger@TA detectors in the field. This work directly supports the installation and commissioning of Auger@TA which will operate to collect cosmic ray air shower data from 2024 to 2026.

PhD, University of Cincinnati, 2024, Arts and Sciences: Physics

I present six strongly gravitationally lensed Lyα Emitters (LAEs) at z ~ 4-5 with HST narrowband imaging isolating Lyα. Through complex radiative transfer, Lyα encodes information about the spatial distribution and kinematics of the neutral hydrogen upon which it scatters. This information can help explain how star-forming galaxies contributed to Reionization. The primary goal of this work is to investigate the galaxy properties and Lyα morphologies of this sample. Many previous studies of high-redshift LAEs have been limited in Lyα spatial resolution. In this work I take advantage of high-resolution Lyα imaging boosted by lensing magnification, allowing for probing of sub-galactic scales that are otherwise inaccessible at these redshifts. I use broadband imaging from HST (rest-frame UV) and Spitzer (rest-frame optical) in SED fitting; providing estimates on the stellar masses ( ~ 108 - 109 M⊙), stellar population ages (t50 < 40 Myr), and amounts of dust (A V ~ 0.1 - 0.6, statistically consistent with zero). I employ non-parametric star-formation histories to probe the young stellar-populations which create Lyα. I also examine the offsets between the Lyα and stellar continuum, finding small upper limits of offsets (<0.1") consistent with studies of low-redshift LAEs, indicating our galaxies are not interacting or merging. I find a bimodality in the sample's Lyα morphologies: clumpy and extended. Comparing these morphologies to the inferred galaxy properties, I find a suggestive trend: our LAEs with clumpy Lyα are generally younger than the LAEs with extended Lyα, suggesting a possible correlation with age. Finally, I present preliminary results from new, state of the art forward modeling code for one object in the sample. I find that intrinsic clump sizes between Lyα and the stellar continuum are statistically equivalent, possibly indicating the presence of ionized channels in the ISM.

Doctor of Philosophy, The Ohio State University, 2024, Astronomy

Brown dwarfs are substellar objects approximately an order of magnitude more massive than Jupiter but below the threshold necessary to burn hydrogen and become main-sequence stars. Although we have learned much about the atmospheres of brown dwarfs, and lower mass planetary-mass objects, over the past 30 years since the first observation of such an object, open questions remain about the driver of these objects' variability. Brown dwarfs, particularly those at the L/T spectral transition (Teff ~ 1300K), exhibit high spectroscopic and photometric variability which has been attributed to dynamic atmospheric processes. Theories invoking storms and vortices (spotted-models) and planetary-scale waves contained within Jupiter-like banded-structures (wave models) have been proposed to explain this variability. To address these mysteries, I first developed a unified analytical spectroscopic and photometric technique to infer surface inhomogeneities on stellar and substellar objects. The method was validated against archival data of Luhman 16B, a nearby, L/T transition brown dwarf. I then used the analytical technique to predict Doppler imaging performance for planned extremely large telescope spectrographs. I found these instruments capable of mapping the surfaces of brown dwarfs and planetary-mass objects such as VHS 1256 b, SIMP0136, and Beta Pic b. To further test my analytical framework, I applied it to real-world spectra collected at the Large Binocular Telescope, detecting a persistent polar dark spot on a pre-main sequence, T Tauri star. The extent of the spot suggested non-solar like dynamo processes. To conclude, I applied both spotted and wave models to multi-color, near-infrared (NIR) photometry of SIMP0136. Based on goodness-of-fit tests, I find wave models to be preferred. Moreover, the spotted models' inferred radii are unphysical based on the Rossby deformation radius and Rhines' scale. Through the correlation between light curves produced by the waves and as (open full item for complete abstract)

Doctor of Philosophy (PhD), Ohio University, 2024, Physics and Astronomy (Arts and Sciences)

As more wide-angle, large-scale, all-sky surveys become available so do opportunities for significant advancements into our understanding of the Universe through the study of formation and evolution of structure and testing cosmological models. It is important to address the systematic errors of weak lensing measurements as statistical errors improve, especially those that are planned as part of an automated process such as pipelines for the Vera Rubin Observatory's Legacy Survey of Space and Time. I obtained and analyzed images from 14 Hubble Space Telescope Advanced Camera for Surveys Wide Field Camera galaxy clusters spanning redshifts from 0.4 to 0.9 to identify potential galaxy cluster centroids and determine the optimal centroid usage based on observable indicators. I utilized the Principal Component Analysis method on individual exposures to describe the point spread function and the KSB+ method to correct the galaxy shapes and measure the shear. I then performed a bootstrap resampling analysis to identify the weak lensing centroid for each cluster. I compared this centroid with the brightest cluster galaxy (BCG), light and X-ray centroids to determine which centroid was optimal. I also searched for observable markers indicating when it is beneficial to use which centroid. My analysis of the survey suggests the BCG as the better choice of center compared to light or X-ray centroids, but is still offset from the mass centroid at a statistically significant level in a number of the clusters. I found no clear indicator within my research of an ideal centroid choice.

Master of Science (M.S.), University of Dayton, 2024, Aerospace Engineering

This research introduces an Origami-inspired dynamic spacecraft radiator, capable of adjusting heat rejection in response to orbital variations and extreme temperature fluctuations in lunar environments. The research centers around the square twist origami tessellation, an adaptable geometric structure with significant potential for revolutionizing radiative heat control in space. The investigative involves simulations of square twist origami tessellation panels using vector math and algebra. This study examines both a two-dimensional (2- D), infinitely thin tessellation, and a three-dimensional (3-D), rigidly-foldable tessellation, each characterized by an adjustable closure or actuation angle “φ”. Meticulously analyzed the heat loss characteristics of both the 2D and 3D radiators over a 180-degree range of actuation. Utilizing Monte Carlo Ray Tracing and the concept of “view factors”, the study quantifies radiative heat loss, exploring the interplay of emitted, interrupted, and escaped rays as the geometry adapts to various positions. This method allowed for an in-depth understanding of the changing radiative heat loss behavior as the tessellation actuates from fully closed to fully deployed. The findings reveal a significant divergence between the 2D and 3D square twist origami radiators. With an emissivity of 1, the 3D model demonstrated a slower decrease in the ratio of escaped to emitted rays (Ψ) as the closure/actuation angle increased, while the 2D model exhibited a more linear decline. This divergence underscores the superior radiative heat loss control capabilities of the 2D square twist origami geometry, offering a promising turndown ratio of 4.42, validating the model's efficiency and practicality for radiative heat loss control. Further exploration involved both non-rigidly and rigidly foldable radiator models. The non-rigidly foldable geometry, initially a theoretical concept, is realized through 3D modeling and physica (open full item for complete abstract)

Doctor of Philosophy, University of Toledo, 0, Physics

Current methods of identifying the ionizing source of nebular emission in galaxies are well defined for the era of single-fiber spectroscopy, but still struggle to differenti- ate the complex and overlapping ionization sources in some galaxies. With the advent of integral field spectroscopy, the limits of these previous classification schemes are more apparent. We propose a new method for distinguishing the ionizing source in resolved galaxy spectra by use of a multidimensional diagnostic diagram that com- pares emission-line ratios with velocity dispersion on a spaxel-by-spaxel basis within a galaxy. This new method is tested using the Sydney-Australian-Astronomical- Observatory Multi-object Integral-Field Spectrograph Galaxy Survey (SAMI) Data Release 3 (DR3), which contains 3068 galaxies at z < 0.12. Using the results of our new classification method, we also investigate the prevalence of outflows and their spatial correlation to both shock and AGN excitation. We find that globally, out- flows are most associated with non-star-forming ionization and are strongest in cases of AGN dominated ionization, while the trend is less noticeable for individual galax- ies. Finally, we investigate a population of 251 low-mass spiral galaxies with high emission line ratios and no other signatures of either shock or AGN excitation. These galaxies have kinematics and WISE colors that suggest they are dominated by simple star formation.

Master of Science (MS), Ohio University, 0, Physics and Astronomy (Arts and Sciences)

The proton structure of 11B, which can be studied via proton induced reactions or transfer reactions on 10Be, has numerous applications in nuclear astrophysics. Reactions involving 10Be play a significant role in Core-Collapse Supernovae and in Big-Bang Nucleosynthesis. Additionally, the structure of 11B above neutron thresholds is important for neutron detection. Recently published work proposes a new excited state for 11B at Ex = 11.4 MeV. However this work finds no evidence for the existence of this resonance. An initial investigation into the proton structure of 11B was conducted at Edwards Accelerator Laboratory by studying the 10Be(d, n)11B reaction employing deuteron beam energies of seven, eight, and nine MeV. The resulting neutrons were measured at 0◦ by a detector located in a neutron time of flight tunnel. Through time of flight methods, populated states of 11B were studied via differential cross section measurements with particular interest at higher excitation energies.

Doctor of Philosophy, The Ohio State University, 2023, Physics

Low-mass galaxies provide an exciting opportunity to learn about many open questions in astronomy, including topics as seemingly disparate as galaxy formation and evolution and the particle nature of dark matter. To take full advantage of these galaxies however, we must devote energy to understanding the basics about their mass and environment. Traditionally this requires distance measurements that use expensive space-based imaging or spectra. An alternative approach is to exploit the discrete nature of galaxy stellar populations to measure so called surface brightness fluctuations (SBF), which change as a function of distance. SBF can provide accurate distances to galaxies without the stringent observational requirements necessary for other distance techniques and often without the need for extensive follow-up data after discovery. Given the huge number of low-mass galaxies being discovered in recent surveys and the upcoming deep imaging observatories that will undoubtedly uncover even more such galaxies, SBF offers a promising solution to obtaining distances to a revolutionary sample of these fascinating systems. In this dissertation, I develop an image processing pipeline with the goal of measuring SBF distances to dwarf galaxies with the Large Binocular Telescope. First, I demonstrate the technique with a quenched galaxy called Blobby in the outskirts of the M81 group. I use the measured distance to argue that Blobby is part of an understudied population of galaxies called backsplash galaxies, and that its mass and stellar population have likely been significantly affected by a past interaction with the group. Next, I measure the SBF of several other Local Volume galaxies, some with widely respected tip of the red giant branch (TRGB) distance measurements. I demonstrate that SBF is competitive with other distance methods and confirm (or reject) associations of dwarfs in the sample with several host galaxies. I discuss challenges with the SBF method, particula (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2023, Physics

Galactic winds are prevalent in galaxies with high rates of star formation, both near us and in distant regions of the universe. These winds play a crucial role in shaping the brightness distribution of galaxies, influencing their chemical composition and determining the relationship between their mass and metal content. They also impact how stars form over time and distribute metals throughout the vast spaces between galaxies. Despite their significance, the exact mechanisms behind these winds remain a mystery. The leading picture is that collective supernovae drive out a hot wind that ram-pressure accelerates cool clouds. In some regimes, clouds die. For other parameter spaces, clouds survive and become accelerated. Understanding multi-phase winds is a daunting computational and analytical task. Additionally, to make matters worse, there's a gap between what theories suggest and what we actually observe for just the hot phase. Recent data on the movement and composition of gases in the hot phase of galactic winds across numerous galaxies haven't been fully explained by existing models. To address this, I introduce augmentations to existing toy hot-wind models focused on including the effects of mass-loading from cool cloud destruction and entrainment, as well as the effects of non-spherical flow geometry from collimation. I show that winds that undergo either mass-loading from cool cloud entrainment or non-spherical divergence exhibit similar qualitative features in their thermodynamic and kinematic evolutions. Namely, the temperature, density, and pressure all decrease at a slower rate than that of a spherical adiabatic wind. I show that the entropy profile is a hallmark of mass-loading, and derive conditions to observe increase/decreasing entropy gradients, and the implications on corresponding minimum/maximum bulk gas velocity. I apply these models to both recent 3D time-dependent hydrodynamic simulation results and observations of starburst galaxy M82, s (open full item for complete abstract)

PhD, University of Cincinnati, 2023, Arts and Sciences: Physics

The cosmic microwave background (CMB) is a snapshot of the universe at recombination, the moment when the universe became transparent. Understanding the CMB could allow us to constrain or rule out aspects of inflation theory, which suggests that the Universe underwent a period of rapid expansion mere moments after the Big Bang. Specifically, we hope to detect primordial gravitational waves (PGW), an as yet unobserved phenomenon predicted by many inflationary models. BICEP/Keck is an experiment based at the South Pole with telescopes that are specified to observe B-mode polarization patterns caused by PGW at microwave wavelengths. The tensor-to-scalar ratio r is a parameter which if constrained could provide indirect evidence of PGWs. Presented is the work I have done in an internal linear combination (ILC) component separation method to separate the CMB signal from galactic foregrounds while minimizing noise, and the likelihood analysis I performed with the ILC results in an effort to constrain r.

Doctor of Philosophy, The Ohio State University, 2023, Physics

The Dark Energy Spectroscopic Instrument (DESI) is a purpose built instrument on the Mayall 4-meter telescope in Kitt Peak, Arizona. It is undertaking an ambitious, 5 year survey of the same name to measure the redshifts of 40 million galaxies and quasars. At the time of writing DESI is about 2 years into its 5 year survey. With the vast new dataset collected by DESI, the DESI collaboration will produce novel constraints on cosmology and in particular the nature of dark energy using techniques such as Baryon Acoustic Oscillations and Redshift Space Distortions. In this work I detail some of my contributions to the success of DESI as a survey. These include in particular the design and writing of software for the Focal Plane System and its novel robotic fiber positioners as well as the commissioning of the Focal Plane system and continued support in the early survey. This does not include earlier work on testing and verifying positioner robots off of the production line. This document will also cover an exploration into a new method to account for systematics in clustering measurements resulting from the DESI instrument. The chapters will proceed as follows. The first chapter will provide a brief introduction to our cosmological universe, concluding with its statistical fluctuations and how we measure the fluctuations. The second chapter will introduce the DESI instrument, the survey it is undertaking and its key operational loop. The third chapter will cover the development of the focal plane software used through commissioning, its structure, and will conclude with some performance statistics. The fourth chapter will cover the commissioning of the focal plane, challenges encountered and key moments. The fifth and final chapter will discuss the imputation of galaxies into DESI clustering catalogs, this is an exploration into a potential new way to account for systematics resulting from the design of DESI and its survey.

Master of Science, The Ohio State University, 2023, Astronomy

We compare the chemical abundance ratios from five sets of one-dimensional core collapse supernova simulations to empirical yields from chemical evolution modeling and to eleven supernova remnants (SNRs) from the literature. All five sets underproduce Mg relative to O compared to the empirical yields. For most, they underproduce Mg relative to other α elements as well. However, the SN yields from simulations agree better with individual SNR abundance ratios, although the degree of matching differs between models. Additionally, the Mg depletion is not universally seen when comparing to individual SNR yields. We show that mixing of the SN ejecta with circumstellar material does not have a noticeable effect on our O/Mg, S/Mg, and Si/Mg ratios. It is possible that the SNRs are a biased sample of masses, or that the empirical yields are incorrect.