Matching Items (31)
Description
3D models of white dwarf collisions are used to assess the likelihood of double-degenerate mergers as progenitors for Type Ia supernovae (henceforth SNIa) and to identify observational signatures of double-degenerate collisions. Observations of individual SNIa, SNIa rates in different galaxy types, and double white dwarf binary systems suggest that mergers or collisions between two white dwarfs play a role in the overall SNIa population. Given the possibility of two progenitor systems (single-degenerate and double-degenerate), the sample of SNIa used in cosmological calcula- tions needs to be carefully examined. To improve calculations of cosmological parameters, the development of calibrated diagnostics for double-degenerate progenitor SNIa is essential. Head-on white dwarf collision simulations are used to provide an upper limit on the Ni-56 production in white dwarf collisions. In chapter II, I explore zero impact parameter collisions of white dwarfs using the Eulerian grid code FLASH. The initial 1D white dwarf profiles are created assuming hydrostatic equilibrium and a uniform composition of 50% C-12 and 50% O-16. The masses range from 0.64 to 0.81 solar masses and have an isothermal temperature of 10^7 K. I map these 1D models onto a 3D grid, where the dimensions of the grid are each eight times the white dwarf radius, and the dwarfs are initially placed four white dwarf radii apart (center to center). To provide insight into a larger range of physical possibilities, I also model non-zero impact parameter white dwarf collisions (Chapter III). Although head-on white dwarf collisions provide an upper limit on Ni-56 production, non-zero impact parameter collisions provide insight into a wider range of physical scenarios. The initial conditions (box size, initial separation, composition, and initial temperature) are identical to those used for the head-on collisions (Chapter II) for the same range of masses. For each mass pair- ing, collision simulations are carried out at impact parameters b=1 and b=2 (grazing). Finally, I will address future work to be performed (Chapter IV).
ContributorsHawley, Wendy Phyllis (Author) / Timmes, Frank (Thesis advisor) / Young, Patrick (Committee member) / Starrfield, Sumner (Committee member) / Fouch, Matt (Committee member) / Patience, Jennifer (Committee member) / Arizona State University (Publisher)
Created2012
Description
As the detection of planets become commonplace around our neighboring stars, scientists can now begin exploring their possible properties and habitability. Using statistical analysis I determine a true range of elemental compositions amongst local stars and how this variation could affect possible planetary systems. Through calculating and analyzing the variation in elemental abundances of nearby stars, the actual range in stellar abundances can be determined using statistical methods. This research emphasizes the diversity of stellar elemental abundances and how that could affect the environment from which planets form. An intrinsic variation has been found to exist for almost all of the elements studied by most abundance-finding groups. Specifically, this research determines abundances for a set of 458 F, G, and K stars from spectroscopic planet hunting surveys for 27 elements, including: C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ba, La, Ce, Nd, Eu, and Hf. Abundances of the elements in many known exosolar planet host stars are calculated for the purpose investigating new ways to visualize how stellar abundances could affect planetary systems, planetary formation, and mineralogy. I explore the Mg/Si and C/O ratios as well as place these abundances on ternary diagrams with Fe. Lastly, I emphasize the unusual stellar abundance of τ Ceti. τ Ceti is measured to have 5 planets of Super-Earth masses orbiting in near habitable zone distances. Spectroscopic analysis finds that the Mg/Si ratio is extremely high (~2) for this star, which could lead to alterations in planetary properties. τ Ceti's low metallicity and oxygen abundance account for a change in the location of the traditional habitable zone, which helps clarify a new definition of habitable planets.
ContributorsPagano, Michael (Author) / Young, Patrick (Thesis advisor) / Shim, Sang-Heon (Committee member) / Patience, Jennifer (Committee member) / Desch, Steven (Committee member) / Anbar, Ariel (Committee member) / Arizona State University (Publisher)
Created2014
Description
The only elements that were made in significant quantity during the Big Bang were hydrogen and helium, and to a lesser extent lithium. Depending on the initial mass of a star, it may eject some or all of the unique, newly formed elements into the interstellar medium. The enriched gas later collapses into new stars, which are able to form heavier elements due to the presence of the new elements. When we observe the abundances in a stellar regions, we are able to glean the astrophysical phenomena that occurred prior to its formation. I compile spectroscopic abundance data from 49 literature sources for 46 elements across 2836 stars in the solar neighborhood, within 150 pc of the Sun, to produce the Hypatia Catalog. I analyze the variability of the spread in abundance measurements reported for the same star by different surveys, the corresponding stellar atmosphere parameters adopted by various abundance determination methods, and the effect of normalizing all abundances to the same solar scale. The resulting abundance ratios [X/Fe] as a function of [Fe/H] are consistent with stellar nucleosynthetic processes and known Galactic thin-disk trends. I analyze the element abundances for 204 known exoplanet host-stars. In general, I find that exoplanet host-stars are not enriched more than the surrounding population of stars, with the exception of iron. I examine the stellar abundances with respect to both stellar and planetary physical properties, such as orbital period, eccentricity, planetary mass, stellar mass, and stellar color. My data confirms that exoplanet hosts are enriched in [Fe/H] but not in the refractory elements, per the self-enrichment theory for stellar composition. Lastly, I apply the Hypatia Catalog to the Catalog of Potentially Habitable Stellar Systems in order to investigate the abundances in the 1224 overlapping stars. By looking at stars similar to the Sun with respect to six bio-essential elements, I created maps that have located two ``habitability windows'' on the sky: (20.6hr, -4.8deg) and (22.6hr, -48.5deg). These windows may be of use in future targeted or beamed searches.
ContributorsHinkel, Natalie R (Author) / Timmes, Frank X (Thesis advisor) / Anbar, Ariel (Committee member) / Patience, Jennifer (Committee member) / Shumway, John (Committee member) / Young, Patrick (Committee member) / Arizona State University (Publisher)
Created2012
Description
The formation of the firsts stars some 100-300 Myr after the Big Bang marked the end of the cosmic darks ages and created the elemental building blocks of not only rocky planets but eventually us. Understanding their formation, lifetimes, and contributions to the evolution of our universe is one of the current frontiers in astronomy and astrophysics.
In this work I present an improved model for following the formation of Pop III stars, their effects on early galaxy evolution, and how we might search for them. I make use of a new subgrid model of turbulent mixing to accurately follow the time scales required to mix supernova (SN) ejecta -- enriched with heavy elements -- into the pristine gas. I implement this model within a large-scale cosmological simulation and follow the fraction of gas with metallicity below a critical value marking the boundary between Pop III and metal enriched Population II (Pop II) star formation. I demonstrate that accounting for subgrid mixing results in a Pop III stars formation rate that is 2-3 times higher than standard models with the same physical resolution.
I also implement and track a new "Primordial metals" (PM) scalar that tracks the metals generated by Pop III SNe. These metals are taken up by second generation stars and likely result in a subclass of carbon-enhanced, metal-poor (CEMP) stars. By tracking both regular metals and PM, I can model, in post-processing, the elemental abundances of simulation stars. I find good agreement between observations of CEMP-no Milky Way halo stars and second generation stars within the simulation when assuming the first stars had a typical mass of 60 M☉, providing clues as to the Pop III initial mass function.
In this work I present an improved model for following the formation of Pop III stars, their effects on early galaxy evolution, and how we might search for them. I make use of a new subgrid model of turbulent mixing to accurately follow the time scales required to mix supernova (SN) ejecta -- enriched with heavy elements -- into the pristine gas. I implement this model within a large-scale cosmological simulation and follow the fraction of gas with metallicity below a critical value marking the boundary between Pop III and metal enriched Population II (Pop II) star formation. I demonstrate that accounting for subgrid mixing results in a Pop III stars formation rate that is 2-3 times higher than standard models with the same physical resolution.
I also implement and track a new "Primordial metals" (PM) scalar that tracks the metals generated by Pop III SNe. These metals are taken up by second generation stars and likely result in a subclass of carbon-enhanced, metal-poor (CEMP) stars. By tracking both regular metals and PM, I can model, in post-processing, the elemental abundances of simulation stars. I find good agreement between observations of CEMP-no Milky Way halo stars and second generation stars within the simulation when assuming the first stars had a typical mass of 60 M☉, providing clues as to the Pop III initial mass function.
ContributorsSarmento, Richard John (Author) / Scannapieco, Evan (Thesis advisor) / Windhorst, Rogier (Committee member) / Young, Patrick (Committee member) / Timmes, Frank (Committee member) / Patience, Jennifer (Committee member) / Arizona State University (Publisher)
Created2018
Description
I saw a Dove ad called "Real Beauty Sketches" where a group of women described themselves to a sketch artist, and then a complete stranger described them to the same artist. By the end of the ad, it's apparent that the women, when describing themselves, were very critical of all their features. When total strangers described them the resulting portrait was more beautiful to the women. The take-away from the campaign was that others see more beauty in you than you do in yourself. I explored that idea through my thesis. My aim in this project was to learn to see the beauty in myself through personal artistic expression. I completed a series of self-portraits; for about four months straight I drew one portrait of myself every single day. I also recorded my thoughts in a diary entry as I drew my portrait, hoping to capture my emotions and moods during that day. The resulting outcome of my creative project is twofold. The physical outcome is about 100 self-portraits and daily diary entries that represent the creative thesis project I pursued. The second outcome cannot be physically seen. I have discovered more about myself in four months than I have in twenty years. I have begun to see myself differently, and positively. This thesis project turned into a journey of self-exploration, and I'm looking forward to what the future holds for me.
ContributorsRao, Rachana Sai (Author) / Hood, Mary (Thesis director) / Button, Melissa (Committee member) / School of Art (Contributor) / W. P. Carey School of Business (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
How do we visualize environments outside our solar system? I have researched two very alien planets and their compositions with the goal of finding out how those differences would affect the way a planet appears on its surface. The first is a planet orbiting the nearby G type star Tau Ceti. This star has Mg/Si ratio of 1.78, compared to 1.2 found on the Earth. A planet formed around this star could have a very active surface, covered in volcanoes. The other planet is a hypothetical carbon planet that could orbit the star HD 144899. This star has a C/O ratio of 0.8, compared to 0.5 in the Sun. A planet formed here might be comprised mostly of carbides, with a hydrocarbon atmosphere. It would likely be geologically dead, the main forces shaping its surface being meteorites. Both planets, due to their extremes, would likely be barren and lifeless. The results of this project are two digital paintings showcasing my vision of these planets.
ContributorsGonzales, Joshua Michael (Author) / Young, Patrick (Thesis director) / Patience, Jennifer (Committee member) / Button, Melissa (Committee member) / Barrett, The Honors College (Contributor) / School of International Letters and Cultures (Contributor) / School of Art (Contributor)
Created2015-05
Description
Curative arts and art therapy have been increasingly implicated in promoting health and well-being for patients, but little research has been done for the benefits of drawing therapy for stress management or individuals in a non-diseased state. College students and healthcare professionals are particularly susceptible to high levels of stress, as I experienced firsthand as a medical scribe in the Emergency Room during my undergraduate experience. For this reason, I wanted to focus on using curative arts as a mediator for high-stress situations. My creative project is therefore a portable framework for curative drawing. The framework is designed to help people process complex emotional states in a more effective way using mark-making and color. Specifically, the framework is designed for those who have limited experience with art making but can be used by anyone who feels a need for curative drawing. I used this framework in both individual and group settings, culminating in a final gallery show in which viewers were able to participate in the framework and take home a booklet with the framework printed inside. In conjunction with outside research, the help of my thesis committee, and the students of Drawing and Painting as Seeing and Thinking, the final project can be viewed as one part of the intersection between art and medicine in our ever-changing healthcare environment.
ContributorsCadigan, Megan Sierra (Author) / Button, Melissa (Thesis director) / Belgrave, Melita (Committee member) / School of Art (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Human nature drives us to focus primarily on the present or near-future, instead of considering what consequences our actions may have many years from now. However, in a new era that is increasingly dominated by humans and their ambitions, this tendency has destructive repercussions on the very environment that once supported and nurtured humankind. Wild animals are highly susceptible to human activities that damage ecosystems, and a loss of animal diversity can have unforeseen consequences on future human populations. In the research, I examine the avoidable reasons for the severe decline in population of four animal species, and through my art, imagine the losses associated with their disappearance. The artwork created evokes an emotional response in the viewer through dramatic, contrasting imagery, making them reassess the relationship between humans, animals and the environment.
ContributorsJudge, Nicole (Author) / Button, Melissa (Thesis director) / Hogden, Heidi (Committee member) / School of Art (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
DescriptionThrough artist book, printed photographs, paintings, writing, and web design, August Tang deconstructed their identity as a nonbinary person. Both educational and expressive, the creative project was a manifestation of a coming out journey, affirmation of gender identity, and experiences relating to gender with friends, family, and strangers.
ContributorsTang, August B (Author) / Button, Melissa (Thesis director) / Sanft, Alfred (Committee member) / School of Art (Contributor) / Dean, W.P. Carey School of Business (Contributor) / The Design School (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
To many, South Phoenix has a negative reputation of being an area full of crime, drugs and poverty. Throughout its foundation, South Phoenix has experienced many changes that have affected the quality of life of its people. The purpose of this creative project was to portray the history of South Phoenix through mural paintings. This thesis, explores a creative proposal to bring history-based murals on the streets of South Phoenix. Three large-scale paintings were created during this creative project, all corresponding with a segment of history of South Phoenix that has been forgotten by the community and the greater Phoenix area. Through this thesis, the author aims to instill a positive image of hope and determination that this community has demonstrated despite the many challenges they faced. Consequently, the author's intent is to one day carry out these projects on the streets of South Phoenix.
ContributorsTorres, Adrian (Author) / Pomilio, Mark (Thesis director) / Button, Melissa (Committee member) / School of Art (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05