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- Brown dwarfs (2)
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Articles 1 - 16 of 16
Full-Text Articles in Physical Sciences and Mathematics
Effect Of Magnetic Draping On Satellite Galaxies In Clusters, Vanessa Brown
Effect Of Magnetic Draping On Satellite Galaxies In Clusters, Vanessa Brown
Dissertations, Theses, and Capstone Projects
Galaxy evolution has been observed to be influenced by environment. Satellite galaxies orbiting within clusters can experience changes in morphology and composition through various mechanisms such as ram-pressure stripping (RPS), which removes a galaxy’s interstellar medium as it passes through the cluster via direct interaction with the hot intracluster medium gas. An open question is whether intracluster magnetic fields affect galaxy evolution, for example by forming a magnetic layer around infalling galaxies (called magnetic draping) and mitigating gas removal by RPS. Using the code GADGET-3, we compare global properties and mass distributions within identical cluster simulations run with and without …
Using Gaussian Processes To Measure M-Dwarf Rotation Periods From Ground-Based Light Curves, Ryan J. Lebron
Using Gaussian Processes To Measure M-Dwarf Rotation Periods From Ground-Based Light Curves, Ryan J. Lebron
Dissertations, Theses, and Capstone Projects
Stellar rotation is a readily observable characteristic that plays a crucial role in the generation and activity of magnetic fields through a process known as a magnetic dynamo. For low mass main sequence stars, they exhibit fully convective interiors, giving rise to a distinct dynamo mechanism compared to solar-type stars. Examining the rotational speeds of these stars can offer valuable insights into the workings of these mechanisms. To measure these rotation periods, we developed a pipeline to analyze 192 archival light curves of low mass stars observed by the Zwicky Transient Facility (ZTF) by utilizing a combination of Lomb-Scargle and …
Illustris-Tng Simulated Central Black Mass(Mbh) And Galaxy Properties Correlations With A Machine Learning Approach, Imani L. Dindy
Illustris-Tng Simulated Central Black Mass(Mbh) And Galaxy Properties Correlations With A Machine Learning Approach, Imani L. Dindy
Dissertations, Theses, and Capstone Projects
Observationaly it is well established that the masses of central black holes are tightly correlated with galaxy properties, most notably the bulge’s velocity dispersion. Cosmolog- ical hydrodynamical simulations can capture most of these correlations, but it is yet not understood why this occurs. To gain greater insight into central black hole growth we use machine learning algorithms to study the relationship between central black hole mass(MBH) and other galaxy properties at z=0 in the TNG simulations. We find that the central black hole mass can be accurately predicted with just a few galaxy properties only if the central black hole …
Rotation Period Distributions And Light Curve Morphologies Of Low Mass Stars And Young Associations, Mark Popinchalk
Rotation Period Distributions And Light Curve Morphologies Of Low Mass Stars And Young Associations, Mark Popinchalk
Dissertations, Theses, and Capstone Projects
This dissertation is centered around the rotation periods of low-mass stars and association of young stars. Rotation periods are a link to the age of the star, as they lose angular momentum over time. To understand how this angular momentum evolves requires understanding the rotation period distributions of a range of stellar types and ages. Traditionally, M dwarf stars and young stars were challenging to describe due to their intrinsic faintness and dispersed sky positions respectively. I approached this subject from several directions.
Naming Venus: An Exploration Of Goddesses, Heroines, And Famous Women, Kavya Beheraj
Naming Venus: An Exploration Of Goddesses, Heroines, And Famous Women, Kavya Beheraj
Dissertations, Theses, and Capstone Projects
Humans have been observing and romanticizing Venus for more than 5,000 years. However, mapping its surface has nearly always been impossible, since the planet is shrouded in thick clouds. A breakthrough came just fifty years ago with the invention of radar imaging, leading to the discovery (and naming) of hundreds of new features in a relatively short length of time.
The rapid naming of Venus is a case study on the impact of planetary nomenclature — the process of naming features on other worlds. While the act of naming streamlines communication and humanizes alien landscapes, it is subject to bias, …
Stacking The Gamma-Ray Sky To Search For Faint Astrophysical Populations, Yuzhe Song
Stacking The Gamma-Ray Sky To Search For Faint Astrophysical Populations, Yuzhe Song
Dissertations, Theses, and Capstone Projects
Gamma-ray emission can be generated from a wide variety of high-energy astrophysical phenomena, from stellar flares to pulsating neutron stars, and from interstellar clouds to the center of the Milky Way Galaxy. Entering the 13th year of its orbit around Earth, the Fermi Space Gamma-ray Telescope has been continually surveying the γ-ray sky with its Large Area Telescope (LAT) on board. The latest Fermi source catalog contains over 6000 sources. Yet, a lot of sources that are expected to emit γ-rays are not detected, and only small percentages of some populations are detected. For example, solar flares are detected in …
Astrophysics, Cosmology And Particle Phenomenology At The Energy Frontier, Jorge Fernandez Soriano
Astrophysics, Cosmology And Particle Phenomenology At The Energy Frontier, Jorge Fernandez Soriano
Dissertations, Theses, and Capstone Projects
This dissertation consists of two parts, treating significantly separated fields. Each part consists on several chapters, each treating a somewhat isolated topic from the rest. In each chapter, I present some of the work developed during my passage through the graduate program, which has mostly been published elsewhere.
Part I – Cosmic Rays and Particle Physics
- Chapter 1: In this chapter we present an introduction to the topic of cosmic ray physics, with an special focus on the so-called ultra high energy cosmic rays: their potential origins, effects during their propagation between their sources and Earth, the different techniques used …
A Unified Approach To M Dwarf Ages, Rocio Kiman
A Unified Approach To M Dwarf Ages, Rocio Kiman
Dissertations, Theses, and Capstone Projects
Estimating ages of M dwarfs, the lowest mass stars in the Galaxy, is a current unresolved problem in Astrophysics. This dissertation focuses on developing a method to estimate ages for M dwarfs. This method consists of combining different age indicators in a Bayesian framework to achieve a precise age measurement. The age indicators I use are: 1) position in the color-magnitude diagram which is a proxy for effective temperature and luminosity, 2) movement of the stars in the Galaxy, or its 3D kinematics, 3) magnetic activity, measured by the Halpha emission line of the spectrum. In this dissertation I analyze …
Understanding Atmospheres Across The Stellar-Substellar Boundary, Eileen C. Gonzales
Understanding Atmospheres Across The Stellar-Substellar Boundary, Eileen C. Gonzales
Dissertations, Theses, and Capstone Projects
Complexities in the atmospheres of sources that straddle the boundary between low-mass stars and planets drive the spectral features we observe and the fundamental parameters that we derive. In an effort to understand the underlying cause of these spectral features, this work examines low-mass stars and brown dwarfs using two approaches: distance-calibrated spectral energy distributions (SEDs) and atmospheric retrievals. SEDs allow for the determination of semi-empirical fundamental parameters, while atmospheric retrievals allow us to derive the atmospheric structure and composition, as well as extrapolated fundamental parameters for a source. Low-metallicity and high surface gravity sources, known as subdwarfs, are the …
An Accurate Solution Of The Self-Similar Orbit-Averaged Fokker-Planck Equation For Core-Collapsing Isotropic Globular Clusters: Properties And Application, Yuta Ito
Dissertations, Theses, and Capstone Projects
Hundreds of dense star clusters exist in almost all galaxies. Each cluster is composed of approximately ten thousand through ten million stars. The stars orbit in the clusters due to the clusters' self-gravity. Standard stellar dynamics expects that the clusters behave like collisionless self-gravitating systems on short time scales (~ million years) and the stars travel in smooth continuous orbits. Such clusters temporally settle to dynamically stable states or quasi-stationary states (QSS). Two fundamental QSS models are the isothermal- and polytropic- spheres since they have similar structures to the actual core (central part) and halo (outskirt) of the clusters. The …
The Formation Of Fine-Grained Chondrule Rims In Unequilibrated Ordinary Chondrites, John Bigolski
The Formation Of Fine-Grained Chondrule Rims In Unequilibrated Ordinary Chondrites, John Bigolski
Dissertations, Theses, and Capstone Projects
Fine-grained rims are ubiquitous, non-igneous, features that completely or partially envelope the majority of chondrules within the least equilibrated of the unequilibrated ordinary chondrites (UOCs). A detailed examination of such rims in 4 UOC samples less than petrologic type 3.2 was conducted in order to 1) characterize the relative distribution of rims within chondrite samples, 2) inspect differences between fine-grained rims and adjacent matrix material, 3) petrologically analyze the rims and their relationships with chondrule cores, 4) characterize an ungrouped UOC, Northwest Africa 5717, 5) conduct a microanalytical investigation of rim / matrix boundaries to discern relative chronologies of fine-grained …
Characterizing Cool Brown Dwarfs And Low-Mass Companions With Low-Resolution Near-Infrared Spectra, Paige Godfrey
Characterizing Cool Brown Dwarfs And Low-Mass Companions With Low-Resolution Near-Infrared Spectra, Paige Godfrey
Dissertations, Theses, and Capstone Projects
Exoplanet direct detections are reaching the temperature regime of cool brown dwarfs, motivating further understanding of the coolest substellar atmospheres. These objects, T and Y dwarfs, are numerous and isolated in the field, thus making them easier to study in detail than objects in companion systems. Brown dwarf spectral types are derived from spectral morphology and generally appear to correspond with decreasing mass and effective temperature (Teff). However, spectral subclasses of the colder objects do not share this monotonic temperature correlation, indicating that secondary parameters (gravity, metallicity, dust) significantly influence spectral morphology. These secondary atmospheric parameters can provide …
Diffuse Gamma-Ray Emission From Nearby Molecular Clouds As A Probe Of Cosmic Ray Density Variations, Ryan Abrahams
Diffuse Gamma-Ray Emission From Nearby Molecular Clouds As A Probe Of Cosmic Ray Density Variations, Ryan Abrahams
Dissertations, Theses, and Capstone Projects
We analyze gamma-ray emission from nearby, interstellar molecular clouds in order to calibrate current tracers of the interstellar medium and to probe local cosmic ray gradients. Gamma-rays detected by the Fermi Gamma-ray Space Telescope are created when cosmic rays collide with atomic nuclei in the interstellar medium, and thus provide a unique, unbiased view of the distribution of gas. The gamma-ray flux per proton in the interstellar medium, also known as the gamma-ray emissivity, contains information about the density of high energy cosmic rays. These cosmic rays are born in supernovae shock waves and diffuse throughout the Galaxy. The cosmic …
Comprehensive Mass Balance Isotope Schematics For Determining The Provenance Of The Moon Forming Impactor., John C. Wolbeck
Comprehensive Mass Balance Isotope Schematics For Determining The Provenance Of The Moon Forming Impactor., John C. Wolbeck
Dissertations, Theses, and Capstone Projects
The goal of this research was to identify areas where deviations from the canonic Moon forming impact scenario (an impactor approximately 12% of the mass of the Earth merging with 100% accretion efficiency with a proto-Earth each of which has a differentiated homologous anatomy of 30% iron and 70% silicates) may greatly reduce the efficacy of the impact mass balance analytics used to determine the provenance of the impactor based on isotope data from terrestrial and lunar samples and physical data from high resolution SPH computer simulations.
Modeling the giant Moon forming impact is complicated by a lack of knowledge …
Fundamental Parameters Of The Lowest Mass Stars To The Highest Mass Planets, Joseph C. Filippazzo
Fundamental Parameters Of The Lowest Mass Stars To The Highest Mass Planets, Joseph C. Filippazzo
Dissertations, Theses, and Capstone Projects
The physical and atmospheric properties of ultracool dwarfs are deeply entangled due to the degenerate effects of mass, age, metallicity, clouds and dust, activity, rotation, and possibly formation mechanism on their observed properties. Accurate fundamental parameters for a wide range of substellar objects are crucial to testing stellar and planetary formation theories. To determine these quantities, we construct flux-calibrated spectral energy distributions (SEDs) for 234 M, L, T, and Y dwarfs and calculate bolometric luminosity (Lbol), effective temperature (Teff), mass, surface gravity, radius, spectral indexes, synthetic photometry, and bolometric corrections (BCs) for each object. We use …
The Evolution Of And Starburst-Agn Connection In Luminous And Ultraluminous Infrared Galaxies And Their Link To Globular Cluster Formation, Stephanie L. Fiorenza
The Evolution Of And Starburst-Agn Connection In Luminous And Ultraluminous Infrared Galaxies And Their Link To Globular Cluster Formation, Stephanie L. Fiorenza
Dissertations, Theses, and Capstone Projects
The evolutionary connection between nuclear starbursts and active galactic nuclei (AGN) in luminous infrared galaxies (LIRGs; 1011o
Using new spectrophotometric data, I classify the primary source of IR radiation as being a nuclear starburst or a type of AGN by using the Baldwin-Phillips-Terlevich (BPT) diagrams. I show that for the U/LIRGs in my sample the properties that describe their nuclear starbursts and AGN (e.g. star formation rate (SFR), L[O III], optical D parameter, D4000, and EW(Hδ)) are independent of one another, ensuring that no biases affect correlations between these properties and objects' locations on the BPT diagrams. I then derive …