Astrophysics and Astronomy Commons^™

Unraveling The Physics Of Quasar Jets Using Hst Polarimetry, Devon Clautice

Theses and Dissertations

We present a multiwavelength study of three high-power FR II (quasar) jets -- 3C 273, PKS 0637-752, and 1150+497 -- with an emphasis on new high-quality Hubble Space Telescope (HST) optical polarimetry and Chandra X-ray Observatory imaging. Relativistic jets from active galactic nuclei transport energy and mass from the supermassive black hole’s accretion region out to Megaparsec-scale lobes, with effects that feedback into galaxy formation and cluster energetics. We build on recent work which has called into question our fundamental understanding of FR II jet physics, and suggest that highly-efficient particle acceleration must be taking place in situ …

Temporal And Spectral Analysis Of 1es 2344+514 In Two Flaring States Observed By Veritas, Connor Poggemann

Physics

VERITAS observed the bright blazar 1ES 2344+514 during two flaring periods, one from Dec. 17 to Dec. 18, 2015 (MJD 57373-57374) with a peak flux of ~60% of the Crab and another from Nov. 28 to Dec. 3, 2021 (MJD 59546-59551) with a peak flux of ~20% of the Crab. This blazar, located at a redshift of z = 0.044, is classified as an extreme high-frequency-peaked BL Lacertae object (HBL). It is known to be variable, including several previous day-scale flares: Whipple on Dec. 20, 1995, VERITAS on Dec. 7, 2007, and MAGIC on Aug. 11, 2016. The VERITAS near-nightly …

Sub-Chandrasekhar Type Ia Supernovae Scenarios With Increased Pathways For Neutronization, Fernando Hernan Rivas

Doctoral Dissertations

Type Ia supernovae are thermonuclear explosions of white dwarfs (WD), electron-degenerate cores of old intermediate mass stars(under 8$M_{\odot}$). Reaching energies of $10^{51}$\si{\erg}, they outshine whole galaxies as they synthesize and distribute most of the iron group elements (IGE; V, Cr, Mn, Fe, Co, Ni) into the interstellar medium, thus being one of the main agents in cosmic chemical evolution. Also, given their notably homogeneous lightcurves, they form the last step in the cosmic distance ladder outdistancing Cepheid variables by orders of magnitude. Though calibration of said lightcurves is dependent on a high number of confirmed events, the limits of statistical …

Identifying And Analyzing Multi-Star Systems Among Tess Planetary Candidates Using Gaia, Katie E. Bailey

Electronic Theses and Dissertations

Exoplanets represent a young, rapidly advancing subfield of astrophysics where much is still unknown. It is therefore important to analyze trends among their parameters to learn more about these systems. More complexity is added to these systems with the presence of additional stellar companions. To study these complex systems, one can employ programming languages such as Python to parse databases such as those constructed by TESS and Gaia to bridge the gap between exoplanets and stellar companions. Data can then be analyzed for trends in these multi-star exoplanet systems and in juxtaposition to their single-star counterparts. This research was able …

The Search For Heavily Obscured Active Galactic Nuclei In The Local Universe, Ross Silver

All Dissertations

Active galactic nuclei (AGN) are supermassive black holes (SMBHs) in the center of galaxies that accrete surrounding gas and emit across the entire electromagnetic spectrum. They are the most energetic persistent emitters in the Universe, capable of outshining their host galaxies despite their emission originating from a region smaller than our Solar System. AGN were some of the first sources discovered that helped teach us that there were galaxies outside of our own, and they proved the existence of black holes. Moreover, AGN can give us valuable insights into other branches of astrophysics. For example, they can be used to …

The Loneliest Galaxies In The Universe: A Gama And Galaxy Zoo Study On Void Galaxy Morphology., Lori E. Porter

College of Arts & Sciences Senior Honors Theses

The large-scale structure (LSS) of the Universe is comprised of galaxy filaments, tendrils, and voids. The majority of the Universe’s volume is taken up by these voids, which exist as underdense, but not empty, regions. The galaxies found inside voids are void galaxies and expected to be some of the most isolated objects in the Universe. However, their standard morphology remains poorly studied. This study, using the Galaxy and Mass Assembly (GAMA) data and Galaxy Zoo survey, aims to remedy this. For completeness purposes, we use void galaxies identified by Alpaslan et al. (2014) with stellar masses (M*) of 10 …

Analysis Of A Controlled Approximation For Explicit Integrations Of Stiff Thermonuclear Networks, Nicholas Brey

Masters Theses

The current standard method to solve stiff coupled differential equations relies on implicit integration methods. Explicit methods are generally avoided due to the extremely small and limiting timesteps they allow when the equations are stiff. However, implicit methods are computationally expensive because of the complex calculations that need to be done at each time step. An explicit integration method can do these calculations quicker and, if allowed to take comparable timesteps to the implicit ones, would allow the entire calculation to be done faster. Previous work by Dr. Guidry, Dr. Endeve, Dr. Hix and Dr. Billings has shown that, in …

Exploring The Dependence Of Bulges In Spiral Galaxies On Their Environment, William Jackson Clark

Physics Theses & Dissertations

Recent research has shown a relationship between spiral galaxy satellite populations and the size of spiral bulges. The modern cosmological model of our universe (ΛCDM), does not predict this. Instead, ΛCMD predicts that only the total dynamical mass of a host galaxy should be correlated with satellite populations. We investigate this relationship in regimes other than satellites. In this study we compare the bulge to total mass ratios of spiral galaxies to the number of nearby galaxies within “n” Mpc. We use four papers from literature that calculate bulge to total mass ratios of 189 spiral galaxies using …

Optimal Method For Reconstructing Polychromatic Maps From Broadband Observations With An Aysmmetric Antenna Pattern, Brianna Cantrall, Emory F. Bunn, Solomon Quinn

Honors Theses

Broadband time-ordered data obtained from telescopes with a wavelength-dependent, asymmetric beam pattern can be used to extract maps at multiple wavelengths from a single scan. This technique is especially useful when collecting data on cosmic phenomena such as the Cosmic Microwave Background (CMB) radiation, as it provides the ability to separate the CMB signal from foreground contaminants. We develop a method to determine the optimal linear combinations of wavelengths (“colors”) that can be reconstructed for a given telescope design and the number of colors that are measurable with high signal-to-noise ratio. The optimal colors are found as eigenvectors of a …

Measurement Of Near-Threshold Proton Branching Ratios In 31s Important For Novae, Sudarsan Balakrishnan

LSU Doctoral Dissertations

Classical novae are stellar explosions that contribute to the nucleosynthesis of isotopes on the proton-rich side of the valley of stability up to ⁴⁰Ca. In ONe novae, the incompletely understood reaction rate of ³⁰P(p,γ)³¹S is known to strongly influence the production rate of several stable isotopes such as ³⁰Si, ³¹P, and ^32,33,34S. A precise measurement of this reaction rate has several potential implications towards matching astrophysical observables to the physical composition of the nova site -- the observed elemental abundance ratios of O/S and S/Al have been suggested as useful `thermometers' to gauge …

Monitoring The M-Dwarf Host Stars Of Tess Exoplanet Candidates: Stellar Flares And Habitability, Ashley Lieber

Physics Undergraduate Honors Theses

In the search for life beyond our solar system, the study of M-dwarfs has become increasingly important due to their unique characteristics including their small size, flaring capabilities, and long lifespans. Their small size allows for exoplanet detection due to observable gravitational interactions, and the stellar flares could potentially trigger prebiotic life on exoplanets in the system. Lastly, their long lifespans may provide the conditions necessary to foster prebiotic life and the development of more complex organisms over time. Flare rate is a critical factor in determining the habitability of the exoplanet due to its potential to damage or incubate …

Signal Yields And Detector Modeling In Xenon Time Projection Chambers, And Results Of An Effective Field Theory Dark Matter Search Using Lux Data, Gregory Ransford Carl Rischbieter

Legacy Theses & Dissertations (2009 - 2024)

The nature of dark matter continues to be one of the biggest remaining mysteries in physics. Astrophysical measurements indicate that dark matter makes up more than a quarter of the Universe's total energy density, and it is well-motivated that dark matter is comprised of Weakly Interacting Massive Particles (WIMPs). Direct detection techniques utilizing liquid and gaseous noble elements have become the primary method of probing the potential non-gravitational interactions between WIMPs and Standard Model matter, with the leading technology being the dual-phase Time Projection Chamber (TPC). The Large Underground Xenon (LUX) and its second-generation successor, LUX-ZEPLIN (LZ), are two xenon …

Characterizing Agn Influence On The Calculated Metallicities Of Adjacent Star-Forming Spaxels, Aidan Khelil

Honors Papers

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 …

Accretion Onto A Black Hole At The Center Of A Neutron Star: Nuclear Equations Of State, Sophia Christina Schnauck

Honors Projects

A recent re-examination of Bondi accretion (see Richards, Baumgarte and Shapiro (2021)) revealed that, for stiff equations of state (EOSs), steady-state accretion can only occur for accretion rates exceeding a certain minimum. To date, this result has been explored only for gamma-law equations of state. Instead, we consider accretion onto a small black hole residing at the center of a neutron star governed by a more realistic nuclear EOS. We generalize the relativistic Bondi solution for such EOSs, approximated by piecewise polytropes, and thereby obtain analytical expressions for the accretion rates which were reflected in our numerical simulations. After taking …

Toward Deep Learning Emulators For Modeling The Large-Scale Structure Of The Universe, Neerav Kaushal

Dissertations, Master's Theses and Master's Reports

Multi-billion dollar cosmological surveys are being conducted almost every decade in today’s era of precision cosmology. These surveys scan vast swaths of sky and generate tons of observational data. In order to extract meaningful information from this data and test these observations against theory, rigorous theoretical predictions are needed. In the absence of an analytic method, cosmological simulations become the most widely used tool to provide these predictions in order to test against the observations. They can be used to study covariance matrices, generate mock galaxy catalogs and provide ready-to-use snapshots for detailed redshift analyses. But cosmological simulations of matter …

Brown Dwarf Atmospheres At High Cadence And Spectral Resolution: A Speed Limit On Brown Dwarf Rotation And A Spectroscopic Atlas Of A 1050 K Atmosphere, Megan E. Tannock

Electronic Thesis and Dissertation Repository

Brown dwarfs are sub-stellar objects that form like stars but are not sufficiently massive to sustain hydrogen fusion in their cores. Characterized by cool, molecule-rich atmospheres, brown dwarfs demonstrate great diversity in spectroscopic appearance and share many properties with giant exoplanets. In this thesis I present two investigations: the first is a detailed photometric and spectroscopic study of the three most rapidly rotating brown dwarfs. The second examines a spectrum of a cool brown dwarf at unprecedented spectral resolution and signal-to-noise ratio to study the accuracy of theoretical model photospheres.

Photometric monitoring of brown dwarfs has revealed that periodic variability …

Accretion And Debris Disc Dynamics Around Single And Higher-Order Star Systems, Jeremy L. Smallwood

UNLV Theses, Dissertations, Professional Papers, and Capstones

My research deals with highly topical areas of astrophysics, such as planet habitability, stellar evolution, the origin of fast radio bursts, the evolution of debris discs, and the dynamics of accretion discs in binary and higher-order star systems. Accretion discs around binary star systems are ubiquitous in the galaxy and planet formation is thought to occur within these discs. Circumbinary discs are commonly observed to be misaligned with respect to the binary orbital plane. A misaligned circumbinary disc eventually evolve to a stable orientation, either coplanar or polar with the binary orbital plane. The process of disc alignment has important …

Expanding Band Parameter Analysis Methods For Hed Meteorites And V-Type Asteroids, Noah Adm Haverkamp Frere

Masters Theses

Vesta and Vesta-like asteroids have been convincingly linked, through visible and near-infrared (VNIR; 0.7 - 2.5 µm [micron]) spectral analysis, to a clan of basaltic achondritic meteorites – howardites, eucrites, and diogenites (HEDs). VNIR reflectance spectra of V-type asteroids and HED meteorites have two absorption features centered near 1 µm (Band I) and 2 µm (Band II) caused primarily by Fe²⁺ [iron] and Ca²⁺ [calcium] cations in pyroxene. Previous studies have shown a correlation between the mol% Fs and Wo with the central wavelengths of Band I and Band II, hereafter called Band I Center (BIC) and Band …

Formation Of Supermassive Black Holes In The Early Universe, Arpan Das

Electronic Thesis and Dissertation Repository

The aim of the work presented in this thesis is to understand the formation and growth of the seeds of the supermassive black holes in early universe. Supermassive black holes (SMBH) with masses larger than 10⁸M_Sun have been observed when the Universe was only 800 Myr old. The formation and accretion history of the seeds of these supermassive black holes are a matter of debate. We consider the scenario of massive seed black hole formation which allows gas to directly collapse into a black hole (DCBH) of similar mass. Considering this scenario, we show that the mass …

Comparing Dust In Other Galaxies To Dust In Our Galaxy, Fatima Elkhatib

Senior Theses

Interstellar dust in galaxies has a profound effect on the galaxies’ light output and apparent properties as well as on the physical processes connected to star formation. Therefore, to understand the true properties of the galaxies around us, it is important to understand the dust in those galaxies and compare it to the dust in our galaxy. To do this, we study the effects of dust on background quasars by analyzing interstellar reddening and extinction. It has been shown that many quasars look redder and dimmer than the average quasar when observing them from Earth, due to the dust in …

A Numerical Approach To Modeling Submoons And Investigating Stability Regions, Josephine Spiegelberg

Honors Program Theses

The recent discovery of the Neptune-sized exomoon candidate Kepler-1625bi (Teachey et al. 2018) has prompted a wave of research into the possibility of such a large satellite hosting its own moons, or submoons. These submoons have a lot in common with moons, and lessons from moon stability calculations can help to understand submoon behavior and stability. Past submoon research has focused on determining stability regions for these submoons using simplified models of the body’s tidal evolution (Reid 1973, Conrad 1985, Kollmeier and Raymond 2019). In order to provide a more detailed understanding of submoon behavior, a Fortran N-Body code was …

Creating A Sample Of Off-Color Galaxies Using Big Data Tools, Christopher Becker

Honors Program Theses

This thesis begins an investigation into the presence of off-colored galaxies in the Sloan Digital Sky Survey. Through establishing the emergence and history of Astroinformatics, the thesis introduces the concepts surrounding both off-color galaxies and the Big Data tools helpful in analyzing the data to find them. A discussion of initial implementation methods and revised implementation due to difficulties with previous plans follows. Results are presented, with well in excess of 500,000 candidates for off-color galaxies present in the sample. Conclusions are then drawn regarding such a large sample and the implications this may have on the conventional understanding of …

The Disk Structure Of Late Type Galaxies: Determining The Black Hole Mass Function Of Low Surface Brightness Galaxies Through Logarithmic Spiral Arm Pitch Angle Measurement, Michael S. Fusco

Graduate Theses and Dissertations

This dissertation pertains to the geometric structure of late type (spiral) galaxies, specifically on the relation between the logarithmic spiral pitch angle of the galactic spiral arms with other properties of the galaxy, such as central Supermassive Black Hole (SMBH) mass. Our work continues a study of the Black Hole Mass Function (BHMF) in local galaxies by recording the pitch angles of spiral galaxies with lower surface brightness than were previously included. We also conduct a case study on the structure of an interestingly shaped galaxy, UGC 4599. Previous studies on the topic of spiral arm pitch angles have measured …

Thornado-Hydro: Generalizing Discontinuous Galerkin Methods For A Nuclear Equation Of State For Supernova Hydrodynamics, Brandon Lynn Barker, Eirik Endeve, Anthony Mezzacappa

Chancellor’s Honors Program Projects

No abstract provided.

Measuring Deterministic And Stochastic Gravitational Waves With Pulsar Timing Array Experiments, Kristina Islo

Theses and Dissertations

Pulsar timing arrays (PTAs) are uniquely poised to detect the nanohertz-frequency gravitational waves from supermassive black hole binaries (SMBHBs) formed during galaxy merger. Efforts are underway to observe three species of gravitational signal from these systems: the stochastic ensemble, individual, adiabatic binary inspirals, and bursts with memory. This dissertation discusses all three.

A typical Bayesian search for evidence of a stochastic gravitational wave background from the superposition of many unresolvable SMBHB inspirals requires weeks to months to deliver results. This is due in part to the inclusion of inter-pulsar spatial and temporal correlations induced in PTA data by such a …

The Invisible Sun: Building A Radio Interferometer Telescope, Isobel Curtin

Senior Projects Spring 2019

When we think of astronomy, we often associate the word implicitly with observing astronomical bodies with our own eyes, or from a signal collected in the visible light range. However, there is more information we can collect from these bodies when observing them using other kinds of light, unseen to the naked eye. Radio astronomy is an important tool in an astronomer’s toolkit, and can help us image hidden parts of the universe. Recently, radio astronomy was used to directly image a black hole in the center of a nearby galaxy for the first time!

This projects aims to further …

Using An Astrophysical Model To Characterize Nuclear Dust, Anita N. Dunsmore

Theses and Dissertations

Dust clouds resulting from nuclear explosions are complex phenomena, and knowledge on how they form is lacking. Noting the similarities between supernovae and nuclear explosions led to the concept of modeling a nuclear dust cloud using a supernova simulation. MOCASSIN uses a Monte Carlo approach to model photons traveling through a dust cloud, allowing the cloud's characteristics to be discovered by comparing an observed spectrum to a calculated one and then changing input values to make the spectra match. Data files describing two nuclear fireballs of varying yields were created and analyzed using MOCASSIN, but yielded zero energy spectra. After …

A Microlensing Detection Algorithm For Wide-Field Surveys, Daniel Godines Alcantara

Senior Projects Spring 2018

Gravitational microlensing is a rare event in which the light from a foreground star (source star) is amplified temporarily as it goes around the Einstein radius of another star (lens star). This only occurs when the two stars align with the line of sight of the observer. The significance of microlensing is that it allows for the detection of planets, as when a planet orbiting the lensing star aligns within the Einstein radius, it acts as an additional lens that further amplifies the light. This results in a gaussian-like light curve with an additional deviation on the curve. Unlike transit …

Investigating Brown Dwarf Atmospheres: Gravity, Dust Content, Cloud Structure And Metallicity, Kendra Kellogg

Electronic Thesis and Dissertation Repository

Brown dwarfs are the lowest mass products of star formation. Their low masses don't allow them to sustain, or sometimes even begin, the thermonuclear processes that provide stars with internal energy and the thermal pressure necessary to maintain hydrostatic equilibrium. Thus, their radii and effective temperatures decrease as they age, continually changing their spectral classification. However, it is now a well-known fact that the spectral appearance of ultra-cool dwarfs is governed by more than just temperature. Factors such as gravity, metallicity and cloud distribution play an important role in the structure and composition of ultra-cool dwarf atmospheres and ultimately their …

Search For High-Energy Gamma Rays In The Northern Fermi Bubble Region With The Hawc Observatory, Hugo Alberto Ayala Solares

Dissertations, Master's Theses and Master's Reports

Gamma-ray astronomy is the study of very energetic photons, from E = m_ec² = 0.5x10⁶ eV to > 10²⁰eV. Due to the large span of the energy range, the field focuses on non-thermal processes that include the acceleration and propagation of relativistic particles, which can be found in extreme environments such as pulsars, supernova remnants, molecular clouds, black holes, etc.

The High Altitude Water Cherenkov (HAWC) observatory is an instrument designed for the study of gamma rays in the energy range of 100 GeV to 100 TeV. Using data from the HAWC observatory, a study …