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This work examines star formation in the debris associated with collisions of dwarf and spiral galaxies. While the spectacular displays of major mergers are famous (e.g., NGC 4038/9, ``The Antennae''), equal mass galaxy mergers are relatively rare compared to minor mergers (mass ratio <0.3) Minor mergers are less energetic than

This work examines star formation in the debris associated with collisions of dwarf and spiral galaxies. While the spectacular displays of major mergers are famous (e.g., NGC 4038/9, ``The Antennae''), equal mass galaxy mergers are relatively rare compared to minor mergers (mass ratio <0.3) Minor mergers are less energetic than major mergers, but more common in the observable universe and, thus, likely played a pivotal role in the formation of most large galaxies. Centers of mergers host vigorous star formation from high gas density and turbulence and are surveyed over cosmological distances. However, the tidal debris resulting from these mergers have not been well studied. Such regions have large reservoirs of gaseous material that can be used as fuel for subsequent star formation but also have lower gas density. Tracers of star formation at the local and global scale have been examined for three tidal tails in two minor merger systems. These tracers include young star cluster populations, H-alpha, and [CII] emission. The rate of apparent star formation derived from these tracers is compared to the gas available to estimate the star formation efficiency (SFE). The Western tail of NGC 2782 formed isolated star clusters while massive star cluster complexes are found in the UGC 10214 (``The Tadpole'') and Eastern tail of NGC 2782. Due to the lack of both observable CO and [CII] emission, the observed star formation in the Western tail of NGC 2782 may have a low carbon abundance and represent only the first round of local star formation. While the Western tail has a normal SFE, the Eastern tail in the same galaxy has an low observed SFE. In contrast, the Tadpole tidal tail has a high observed star formation rate and a corresponding high SFE. The low SFE observed in the Eastern tail of NGC 2782 may be due to its origin as a splash region where localized gas heating is important. However, the other tails may be tidally formed regions where gravitational compression likely dominates and enhances the local star formation.
ContributorsKnierman, Karen A (Author) / Scowen, Paul (Thesis advisor) / Groppi, Christopher (Thesis advisor) / Mauskopf, Philip (Committee member) / Windhorst, Rogier (Committee member) / Jansen, Rolf (Committee member) / Arizona State University (Publisher)
Created2013
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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 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.
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
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ContributorsPowell, Devon (Author) / Gardner, Carl (Thesis director) / Scannapieco, Evan (Committee member) / Windhorst, Rogier (Committee member) / Barrett, The Honors College (Contributor)
Created2012-05
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Description
Abstract Located in southeastern Arizona, the Large Binocular Telescope is a great local resource for ASU astronomy/cosmology researchers. As a ground-based observatory, the Large Binocular Telescope can effectively provide deep, complementary observations of science fields in the wavelength range of 3,500 to 10,000 Angstroms. This gives scientists a lot of

Abstract Located in southeastern Arizona, the Large Binocular Telescope is a great local resource for ASU astronomy/cosmology researchers. As a ground-based observatory, the Large Binocular Telescope can effectively provide deep, complementary observations of science fields in the wavelength range of 3,500 to 10,000 Angstroms. This gives scientists a lot of opportunity for various science projects, which can lead to massive amounts of observations being taken by research schools with ties to the LBT. Such is the case with ASU, which has obtained over 30 hours of data in just the SDT Uspec filter on board the Large Binocular Camera (Blue) and much more time in other filters observing longer wavelengths. Because of this, there is a huge need for establishing a system that will allow the reduction of raw astronomical images from the LBT to be quickly, but accurately. This manuscript serves as a presentation of the work done over the 2015-2016 school year to establish a pipeline for reducing LBT raw science images as well as a guide for future undergraduates and graduates to reduce data on their own.
ContributorsVehonsky, Jacob Ryan (Author) / Windhorst, Rogier (Thesis director) / Jansen, Rolf (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
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Description
Standard cosmological models predict that the first astrophysical sources formed from a Universe filled with neutral hydrogen (HI) around one hundred million years after the Big Bang. The transition into Cosmic Dawn (CD) that seeded all the structures seen today can only be probed directly by the 21-cm line of

Standard cosmological models predict that the first astrophysical sources formed from a Universe filled with neutral hydrogen (HI) around one hundred million years after the Big Bang. The transition into Cosmic Dawn (CD) that seeded all the structures seen today can only be probed directly by the 21-cm line of neutral hydrogen. Redshifted by the Hubble expansion, HI signal during CD is expected to be visible in radio frequencies. Precisely characterized and carefully calibrated low-frequency instruments are necessary to measure the predicted ~10-200 mK brightness temperature of this cosmological signal against foregrounds. This dissertation focuses on improving the existing instrumental and analysis techniques for the Experiment to Detect the Global EoR Signature (EDGES) and building capabilities for future space-based 21-cm instruments, including the Farside Array for Radio Science Investigations of the Dark ages and Exoplanets (FARSIDE) concept.Frequency-dependent antenna beams of 21-cm instruments limit the removal of bright galactic foreground emission (~10^3 - 10^4K) from observations. Using three electromagnetic simulation packages, I modeled the EDGES low-band antenna, including the ground plane and soil, and quantified its variations as a function of frequency. I compared simulated observations to sky data and obtained absolute agreement within 4% and qualitatively similar spectral structures. I used the new open-source edges-analysis pipeline to carry out rigorous fits of the absorption feature on the same low-band data and lab calibration measurements as (Bowman et. al. 2018). Using a Bayesian framework, I tested a few calibration choices and found posteriors of the best-fit 21-cm model parameters well within the 1σ values reported in B18. To test for the ``global'' nature of the reported cosmic absorption feature, I performed a time-dependent analysis. Initial results from this analysis successfully retrieved physical estimates for the foregrounds and estimates of the cosmic signal consistent with previous findings. The array layout of FARSIDE, a NASA probe-class concept to place a radio interferometer on the lunar farside, is a four-arm spiral configuration consisting of 128 dual-polarized antennas with a spatial offset between the phase centers of its orthogonal polarizations. I modeled the impact of direction-dependent beams and phase offsets on simulated observations of all four Stokes parameter images of a model and quantified its effects on the two primary science cases: 21-cm cosmology and exoplanet studies.
ContributorsMahesh, Nivedita (Author) / Bowman, Judd D (Thesis advisor) / Jacobs, Daniel C (Committee member) / Groppi, Christopher (Committee member) / Shkolnik, Evgenya (Committee member) / Windhorst, Rogier (Committee member) / Arizona State University (Publisher)
Created2022