Doctor of Philosophy, The Ohio State University, 2022, Astronomy

While the Universe might at first appear static and unchanging to a casual observer, it is teeming with variable sources and cataclysmic events that mark the births, lives, and deaths of the many and varied objects filling our Universe. In recent years, modern time-domain surveys have revolutionized the study of stellar variability by providing access to time series data for millions of stars in the Milky Way. The All-Sky Automated Survey for SuperNovae (ASAS-SN) monitors the entire visible sky daily using 20 robotic telescopes in Hawaii, Texas, Chile, and South Africa. In addition to the real-time detection of bright supernovae and other transients, archival ASAS-SN data allows for the time series characterization of over 100 million stars. By analyzing the ASAS-SN time series data for ~61 million stars, I made the first homogeneous all-sky catalog of bright variable stars and then uniformly classified them using machine learning techniques. This catalog includes the discovery of ~220,000 new variable stars and ~660,000 variables in total. I present studies that use this catalog combined with information from large scale spectroscopic surveys to study various populations of variable stars. Finally, I present examples of the discovery of rare and unusual variable stars using ASAS-SN, including the most extreme 'heartbeat'' star ever discovered.

Committee: Krzysztof Stanek (Advisor); Todd Thompson (Committee Member); Christopher Kochanek (Advisor) Subjects: Astronomy; Astrophysics; Physics

BA, Oberlin College, 2022, Physics and Astronomy

In this thesis, I introduce a method to identify and characterize the effects of active galactic nuclei (AGN) on the spectra of nearby star-forming regions. I analyze spatially-resolved areas of galaxies called “spaxels” within Data Release 15 of the Sloan Digital Sky Survey (SDSS) with the goal of locating those which are physically close to AGN. I find those spaxels with calculated metallicities which lie adjacent to AGN-flagged spaxels and characterize their metallicity values relative to the spaxels which are not adjacent to AGN-flagged spaxels, using a total of 11 separate metallicity calibrations. I find that the current methods to mask AGN-influenced regions for large-scale investigation are, in general, robust, as the largest median deviation between metallicities in border spaxels and those in non-border spaxels is 0.0467 dex. The largest mean difference in metallicity between border and non-border spaxels is 0.0522 dex with a standard deviation of 0.0590 dex. However, on a spaxel-by spaxel basis, I find that the differences in metallicity between border spaxels and non-border spaxels can be as large as 0.9350 dex. These results are concerning for spaxel-by-spaxel analysis, and indicate the need for an improved masking process in the future.

Committee: Jillian Scudder (Advisor) Subjects: Astronomy; Astrophysics; Physics

Master of Science in Computer Engineering, University of Dayton, 2022, Electrical and Computer Engineering

Automated monitoring of low resolution, deep-space objects in wide field of view (WFOV) imaging systems is an important and emerging technology for Space Domain Awareness (SDA). SDA involves the holistic process of monitoring and characterizing space objects in order to ensure a safe environment for satellite operations and employment. With the proliferation of satellites, referred to as ‘Resident Space Objects' (RSOs), in all orbits, SDA requires WFOV optical sensors to detect and track the growing population of multiple low-light objects. The PANDORA sensor array, located in Maui at the Air Force Maui Optical and Supercomputing Site, is an exemplar of a scalable imaging architecture that can detect dim deep- space objects while maintaining a WFOV. The PANDORA system captures 20◦×120◦ images of the night sky oriented along the GEO belt at a rate of two frames per minute. The PANDORA sensor system makes possible the passive monitoring of hundreds of RSOs, but requires advanced image processing and exploitation techniques to autonomously and reliably be utilized. This thesis explores image processing and deep learning techniques to exploit PANDORA sensor data for use in SDA. To benchmark object detection performance, a synthetic dataset and annotated physical dataset of PANDORA imagery is prepared. Classical feature- based object detections are explored, which are tailored to specific space object morphologies in PANDORA imagery. Single frame object detection performance with developed classical methods are evaluated on the synthetic PANDORA dataset. Deep learning object detection techniques are then employed, which set a standard for WFOV low-resolution object detection. We present a deep learning RSO detection and tracking architecture: PASTOR (Persistent All- Sky Tracking and Object Re-Identification). This architecture consists of a deep-learned object detector using YOLOv5, with an object tracker consisting of Kalman filters. We present detailed analysis o (open full item for complete abstract)

Committee: Vijayan Asari (Advisor) Subjects: Computer Engineering; Computer Science

Master of Science, The Ohio State University, 2021, Mechanical Engineering

Spectroscopy is one of the more common scientific practices in the realm of astronomy because it allows astronomers to deduce properties of stars, galaxies, and other celestial objects, such as mass, temperature, chemical composition, redshift, presence of orbiting bodies, and more. Specifically, multi-object spectroscopy has become popular in ground-based astronomy for accumulating large quantities of data. This data is collected with optical fibers located at a telescope's focal plane that then send the collected light to instruments called spectrographs for analysis. Up until recently, these fibers were always fixed in stationary configurations. Now, the astronomy community has begun working with fiber positioning robots that can dynamically and automatically reconfigure the fibers. This functionality allows for more observing time, and thus more data collected, each night that previously would have been spent manually reconfiguring fibers. One such project employing this new strategy is the Sloan Digital Sky Survey (SDSS-V). A lot of work goes into preparing instruments with robotic fiber positioners, and a great deal of effort is put in to retire as much risk as possible before delivery to observatories. This thesis discusses the development and implementation of an optical measurement system that serves to measure the positional accuracy performance of the fiber robots and that is used to develop and exercise the software package to be used with the Focal Plane System instruments of SDSS-V prior to arrival on-site. Specifically, the fixed fiber-illuminated fiducial metrology, opto-mechanical design of the measurement system, and the development of the optical transform to be used to evaluate robot positional accuracy is detailed herein. This lab-based pre-commissioning strategy is unique to the subset of these instruments with connectorized fibers since they can operate without being interfaced with a telescope and spectrograph(s). From a software (open full item for complete abstract)

Committee: Richard Pogge (Committee Member); Giorgio Rizzoni (Advisor) Subjects: Astronomy; Mechanical Engineering; Optics

Bachelor of Arts, Ohio University, 2021, History

Billie Holiday, Lena Horne, and Nina Simone were musicians in the early-mid twentieth century who were innovators for using art as activism. They used their art and platforms to raise awareness and comment on the state of the nation in regards to civil rights. Billie Holiday paved the way with her iconic song "Strange Fruit," calling out racial injustice in the form of lynchings. Lena Horne was a performer who made room for Black actors in Hollywood for roles outside of stereotypes, like servants or "mammies." Nina Simone was a classical pianist who used her strong voice and honest lyrics to narrate the Civil Rights Movement in the 1960s. Their lives demonstrate intersectionality and how Black women used their strength, determination, and art to be part of a movement.

Committee: Chester Pach Dr. (Advisor) Subjects: African American Studies; American History; Black History; Gender; History; Modern History; Music

MFA, Kent State University, 2019, College of the Arts / School of Art

I am a record-keeper of disposable objects that live to be discarded. Such materials include one-and-done supplies like packing materials, sanitation products, and household cleaning supplies. Where contemporary culture views these objects as a means to an end, my work establishes value in them as the end, themselves. In this way, I elevate daily `garbage' to a fine art standard. 
 I use a variety of print media to keep these records including silkscreen, lithography, intaglio, and relief printing, which take the final form of prints, books, collages, installations, and video animations. Whether printing the physical object as a relief, exposing the object onto a screen, or imprinting its form onto a stone, the texture and shape of the material create the most compelling mark that I strive to document.
 The prevalence and quantity of disposable materials is larger than life, and the fibrous forms of these objects are detailed beyond what any human can remember. I intend to present the immensity and complexity of these `garbage' products by dwarfing the viewer through accumulation; this will take the form of an assembled overhead `sky' element that traverses the entirety of the gallery space. My practice is based upon collection and observation, and by presenting the work overhead, I ask my viewer to experience an environment rooted in trash impressions.

Committee: Taryn McMahon (Advisor); Arron Foster (Committee Member); Gianna Commito (Committee Member) Subjects: Fine Arts

Bachelor of Arts, University of Toledo, 2019, English

When Literary scholars take up Kentucky writer Harlan Hubbard, it usually falls within the context of Henry David Thoreau, who greatly influenced Hubbard's work. Writers often praise Hubbard's practical commitment to Thoreauvian philosophy, but in doing so, they limit the depth of his language. These assessments particularly underscore the lack of symbolism present in Hubbard's text. In this paper, I argue that Hubbard's work deserves its own analysis, particularly in terms of his engagement with Thoreau—a relationship writers notice but have not explored in any depth. Hubbard's Payne Hollow, an essentially symbolic text, engages in a literary discussion with Thoreau's Walden. Hubbard answers Thoreau's provocations specifically through symbols, in an attempt to define intentional living and the limitations of perspective. This paper focuses on one particularly salient symbol from Walden that Hubbard re-defines: “Sky water” (473). This image represents, for Thoreau, an intentional picture one must deliberately will the eye to see. Hubbard's text reflects that picture, offering his own challenges to the concept of deliberation.

Committee: Russell Reising Dr. (Advisor); Melissa Gregory Dr. (Advisor) Subjects: Environmental Philosophy; Literature

Doctor of Philosophy, The Ohio State University, 2017, Astronomy

The night sky is replete with transient and variable events that help shape our universe. The violent, explosive deaths of stars represent some of the most energetic of these events, as a single star is able to outshine billions during its final moments. Aside from imparting significant energy into their host environments, stellar deaths are also responsible for seeding heavy elements into the universe, regulating star formation in their host galaxies, and affecting the evolution of supermassive black holes at the centers of their host galaxies. The large amount of energy output during these events allows them to be seen from billions of lightyears away, making them useful observational probes of physical processes important to many fields of astronomy. In this dissertation I present a series of observational studies of two classes of transients associated with the deaths of stars in the nearby universe: tidal disruption events (TDEs) and supernovae (SNe). Discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN), the objects I discuss were all bright and nearby, and were subject to extensive follow-up observational campaigns. In the first three studies, I present observational data and theoretical models of ASASSN-14ae, ASASSN-14li, and ASASSN-15oi, three TDEs discovered by ASAS-SN and three of the most well-studied TDEs ever discovered. Next I present the discovery of ASASSN-13co, an SN that does not conform to the traditional model of Type II SNe. Finally, I discuss the full sample of bright SNe discovered from 2014 May 1 through 2016 December 31, which is significantly less biased than previous nearby SN samples due to the ASAS-SN survey approach, and perform statistical analyses on this population that will be used for future studies of nearby SNe and their hosts.

Committee: Krzyzstof Stanek (Advisor); Christopher Kochanek (Advisor); Todd Thompson (Committee Member) Subjects: Astronomy

MARCH, University of Cincinnati, 2015, Design, Architecture, Art and Planning: Architecture

The sky, earth, and horizon are always with us from our earliest memories: indeed it is impossible to imagine a time or an experience without them. But it is this very proximity that has come to betray us. Further, with the rise of urban dwelling and the concomitant estrangement with the natural condition, people today are not able to appreciate these elemental forces the way they once could. This has contributed to an impoverished understanding of the natural environment.

Committee: Aarati Kanekar Ph.D. (Committee Chair); Michael McInturf M.Arch. (Committee Member) Subjects: Architecture

Doctor of Philosophy, The Ohio State University, 2015, Evolution, Ecology and Organismal Biology

The plant genus Heuchera (Saxifragaceae) consists of more than 40 species of plants largely specific to rock outcrops in montane regions, known for its difficult species delimitation attributable to hybridization and polyploidy. Presented herein are taxonomic and phylogenetic studies intended to clarify the evolution of this plant genus and to elucidate species boundaries in problematic species complexes. A study on whole-genus phylogenetic relationships using six nuclear DNA sequence loci and 39 morpological characters constitutes the first chapter. Following this is a study on species delimitation in the Heuchera parviflora complex using molecular and morphological data. Revisionary studies are afterwards presented which treat taxa occuring in Mexico (heretofore the most problematic of all Heuchera species), treated in two separate chapters to reflect two apparently unrelated circles of affinity among the Mexican taxa, and finally a study of southwestern U.S. species of section Heuchera which are also poorly known. This work is concluded with studies using new sequencing technologies to provide a genomic view of Heuchera: a new method for sequence capture in recently diverged complexes is followed by a phylogenomic study that improves upon the work presented in the first chapter.

Committee: John Freudenstein V (Advisor); Marymegan Daly (Committee Member); Andrea Wolfe D. (Committee Member) Subjects: Biology; Botany; Plant Biology; Plant Sciences

Bachelor of Sciences, Ohio University, 2010, Physics and Astronomy

Galaxy clusters are the largest structures in the Universe, and the evolution of galaxy cluster mass profiles is a useful tool for constraining cosmological models. Most methods established for obtaining a mass profile of a cluster of galaxies assumes the clusters obey the virial theorem; however, the majority of clusters are observed to contain non-virialized substructures. Zaritsky outlined a timing argument for obtaining mass profiles (Zaritsky, 1989). The timing argument assumes that at a time t = 0, every galaxy in the cluster was concentrated at one point, and then simultaneously exploded outward. The current position of each galaxy with respect to the cluster center is determined only by Newtonian gravitation. Zaritsky applied this method to the local group and obtained reasonable mass profiles (Zaritsky, 1989). We test this new method for mass measurement and compare our results to values obtained using virialized methods. We apply this timing argument to a sample of galaxy clusters of nearby redshift (from z~0.05 to z~0.2) taken from the Sloan Digital Sky Survey, using a 12 Mpc radius (a region larger than the typical infall radius) for each cluster. We chose clusters from a paper written by Popesso that contained published velocity dispersions for each cluster (Popesso, 2006). The profiles we acquire through the timing argument have a useful astronomical application because they rely only on infalling galaxies in the cluster, forgoing the virial theorem. We estimate a mass based on these profiles and use that mass to calculate a velocity dispersion in each cluster. Our velocity dispersions are compared to published values. Our comparison shows that this method for mass measurement gives reasonable velocity dispersions when applied to a large sample of galaxies. There is no clear systematic offset between our data set and the published data set, and many variables within this method leave room for large errors.

Committee: Douglas Clowe PhD (Advisor) Subjects: Astronomy; Astrophysics; Physics