Matching Items (9)
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- All Subjects: Astrophysics
- Creators: Department of Physics
Description
Observations of four times ionized iron and nickel (Fe V & Ni V) in the G191-B2B white dwarf spectrum have been used to test for variations in the fine structure constant, α, in the presence of strong gravitational fields. The laboratory wavelengths for these ions were thought to be the cause of inconsistent conclusions regarding the
variation of α as observed through the white dwarf spectrum. This thesis presents 129 revised Fe V wavelengths (1200 Å to 1600 Å) and 161 revised Ni V wavelengths (1200 Å to 1400 Å) with uncertainties of approximately 3 mÅ. A systematic calibration error
is identified in the previous Ni V wavelengths and is corrected in this work. The evaluation of the fine structure variation is significantly improved with the results
found in this thesis.
variation of α as observed through the white dwarf spectrum. This thesis presents 129 revised Fe V wavelengths (1200 Å to 1600 Å) and 161 revised Ni V wavelengths (1200 Å to 1400 Å) with uncertainties of approximately 3 mÅ. A systematic calibration error
is identified in the previous Ni V wavelengths and is corrected in this work. The evaluation of the fine structure variation is significantly improved with the results
found in this thesis.
ContributorsWard, Jacob Wolfgang (Author) / Treacy, Michael (Thesis director) / Alarcon, Ricardo (Committee member) / Nave, Gillian (Committee member) / Department of Physics (Contributor) / Computer Science and Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
I have developed a Java-based application, “Hyper-speed Exploration with Webb” (HEW) based on the previous success of the “Appreciating Hubble at Hyper-speed” (AHaH) program, designed to allow users to explore the James Webb Space Telescope’s North Ecliptic Pole Time-Domain Field (NEP TDF) at super-luminal velocities in a simulated three-dimensional environment. HEW furthermore allows users to explore how the appearance of the NEP TDF might change under hypothetical cosmological parameters alternative to the current Planck spacetime model. In this paper, I explain the rationale behind HEW’s development, detail the development process, and provide an overview of the system’s internal mechanisms. I also explain likely avenues through which HEW might be improved upon in the future.
ContributorsGapinski, Donovan (Author) / Windhorst, Rogier (Thesis director) / Cohen, Seth (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor) / Department of Physics (Contributor)
Created2024-12
Description
The Epoch of Reionization (EoR) is the period in the evolution of the universe during which neutral hydrogen was ionized by the first luminous sources, and is closely linked to the formation of structure in the early universe. The Hydrogen Epoch of Reionization Array (HERA) is a radio interferometer currently under construction in South Africa designed to study this era. Specifically, HERA is dedicated to studying the large-scale structure during the EoR and the preceding Cosmic Dawn by measuring the redshifted 21-cm line from neutral hydrogen. However, the 21-cm signal from the EoR is extremely faint relative to galactic and extragalactic radio foregrounds, and instrumental and environmental systematics make measuring the signal all the more difficult. Radio frequency interference (RFI) from terrestrial sources is one such systematic. In this thesis, we explore various methods of removing RFI from early science-grade HERA data and characterize the effects of different removal patterns on the final 21-cm power spectrum. In particular, we focus on the impact of masking narrowband signals, such as those characteristic of FM radio and aircraft or satellite communications, in the context of the algorithms currently used by the HERA collaboration for analysis.
ContributorsWhitler, Lily (Author) / Jacobs, Daniel (Thesis director) / Bowman, Judd (Committee member) / Beardsley, Adam (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / Department of Physics (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Supernovae are vital to supplying necessary elements to forming bodies in our solar systems. This project studies the creation of a subset of these necessary elements, called short-lived radionuclides (SLRs). SLRs are isotopes with relatively short half-lives and can serve as heat sources for forming planetary bodies, and their traces can be used to date stellar events. Computational models of asymmetric supernovae provide opportunities to study the effect of explosion geometry on the SLR yields. We are most interested in the production of \iso{Al}{26}, \iso{Fe}{60}, and \iso{Ca}{41}, whose decayed products are found in our own solar system. To study the effect of explosion asymmetries in supernovae, we use TYCHO stellar evolution code, SNSHP smooth particle hydrodynamics code for 3D explosion simulations, Burn code for nucleosythesis post-processing, and Python code written to analyze the output of the post-processing code.
ContributorsJohnson, Charlotte (Author) / Young, Patrick (Thesis director) / Lunardini, Cecilia (Committee member) / Department of Physics (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Radio astronomy is a subfield in astronomy that deals with objects emitting frequencies around 10 MHz to 100 GHz. The Low Frequency Array (LOFAR) is a array of radio antennas in Europe that can reach very low frequencies, roughly between 10-240 MHz. Our project was to image and clean a field from LOFAR. The data was a 10 degree square in the sky centered at a right ascension of 10:19:34.608 and a declination +49.36.52.482. It was observed for 600 seconds at 141 MHz. To clean the field, we had to flag and remove any stations that were not responding. Using a program called FACTOR, we cleaned the image and reduced the residuals. Next we checked the validity of our sources. We checked positional offsets for our sources using the TGSS survey at 150 MHz, and corrected the declination of our LOFAR sources by a factor of 0.0002 degrees. We also fixed the LOFAR fluxes by a factor of 1.15. After this systematic check, we calculated the spectral index of our sources using the FIRST survey at 1435 MHz. We plotted this spectral index against LOFAR flux as well as redshift of the sources, and compared these to literature.
ContributorsStawinski, Stephanie Mae (Author) / Scannapieco, Evan (Thesis director) / Windhorst, Rogier (Committee member) / Karen, Olsen (Committee member) / Department of Physics (Contributor) / School of International Letters and Cultures (Contributor) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
The LOw Frequency ARray (LOFAR) is a new and innovative radio telescope designed and constructed by the Netherlands Institute for Radio Astronomy (ASTRON). LOFAR unique capable of operating in very low frequencies (10-240 MHz) and consists of an extensive interferometry array of dipole antenna stations distributed throughout the Netherlands and Europe which allows it to achieve superb angular resolution. I investigate a part of the northern sky to search for rare radio objects such as radio haloes and radio relics that may have not been able to have been resolved by other radio telescopes.
ContributorsNguyen, Dustin Dinh (Author) / Scannapieco, Evan (Thesis director) / Butler, Nathaniel (Committee member) / School of Earth and Space Exploration (Contributor) / Department of Physics (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Recent JWST observations suggest an unpredicted abundance of very bright objects at high redshift, which could be a potential explanation of the 21 centimeter absorption signal measured by EDGES if these objects are producing an excess radio-background. By assuming most of these objects are active-galactic nuclei, an excess radio background can be generated capable of explaining the unexpected depth of the EDGES absorption signal. I will present a model for the absorption signal that constructs an excess radio background, an X-ray heating source, and a Lyman-alpha Coupling model from various UV luminosity extrapolations from JWST observations in order to recreate the EDGES data. I will discuss the physical limitations of using the various UVLF models as well as the constraints presented by X-ray Heating that ultimately destroys the absorption signal if X-ray escape from AGN is too high. I will also explore the redshift evolution of physical parameters in our model required to fit both the depth and shape of EDGES.
ContributorsNelander, Alexandra (Author) / Windhorst, Rogier (Thesis director) / Bowman, Judd (Committee member) / Barrett, The Honors College (Contributor) / Department of Physics (Contributor) / School of Earth and Space Exploration (Contributor)
Created2025-05
Description
We leverage the Illustris TNG50 hydrodynamical simulation to study globular clusters within isolated dwarf galaxies. To do so, we apply a model for globular cluster formation and mass loss to evolve populations of globular clusters throughout the lifetime of 500 simulated dwarf galaxies. By calibrating our model using observations in the local universe, we are able to better understand the formation mechanisms of globular clusters in dwarf galaxies.
ContributorsSummers, Jake (Author) / Windhorst, Rogier (Thesis director) / Carleton, Timothy (Committee member) / Cohen, Seth (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Department of Physics (Contributor)
Created2025-05
Description
In this work, we analyze the nearby, spiral galaxy, NGC 3344. This particular galaxy is
interesting due to its extended UV disk (Padave et al. 2021). NGC 3344 was observed
using broadband optical imaging from the Large Binocular Telescope. We begin with a
photometric analysis of the stellar populations in the inner versus outer disk of the galaxy.
We then present the color as a function of galactocentric distance to infer the age gradient
in NGC 3344. We find a higher ratio of younger stars to older stars in the outer disk,
which indicates that NGC 3344 grows from the inside-out. Then, we use Code Investigating
GALaxy Emission (CIGALE) to model the star formation history of the galaxy. After testing
over 1,469,664 combinations of models, we conclude that NGC 3344 matches the pattern of
a constant star forming galaxy with a delayed burst episode. Based on the modeled star
formation rate, NGC 3344 experienced a 5% increase in star formation 50 million years ago.
This finding corroborates the presence of an extended UV (XUV) disk in the galaxy, which
could be tied to an accretion event of a spiral density wave. These results are very exciting,
and will be explored further in Padave et al. 2025 (in prep).
ContributorsCarl, Naomi (Author) / Borthakur, Sanchayeeta (Thesis director) / Jansen, Rolf (Committee member) / Padave, Mansi (Committee member) / Barrett, The Honors College (Contributor) / School of Music, Dance and Theatre (Contributor) / School of Earth and Space Exploration (Contributor) / Department of Physics (Contributor)
Created2025-05