Degree
Doctor of Philosophy (PhD)
Department
Physics & Astronomy
Document Type
Dissertation
Abstract
Though the confirmed exoplanet population has now reached over 5,500 planets, we still have a plethora of unanswered questions, e.g., regarding their formation mechanisms, true demographics, occurrence rates, and habitability. One remaining question is whether hot Jupiters formed in situ or migrated to their current orbits, so close to their host stars that their periods are 10 days or less. This question can potentially be answered by probing the effects of elemental abundances on hot Jupiter occurrence rates. These rates have been found to correlate with metallicity, but the specific elements responsible for the correlation have largely been unresolved. The correlation is generally given in terms of iron abundance, [Fe/H], specifically, but one alternative is that the abundance of α-elements has more influence than [Fe/H] alone. These elements are present in many of the molecules we expect to be crucial ingredients for giant planet formation: namely, the volatiles and silicates, which may be required to provide the amount of material necessary to form giant planets.
Certain low-[Fe/H], high-[α/Fe] populations such as the Galactic thick disk have higher numbers of giant planets than are predicted from iron abundance alone, and there is yet no conclusive explanation, since our current sample of planet-hosting stars are primarily from the high-[Fe/H], low-[α/Fe] thin disk. The sample is thus biased towards the young, iron-rich, α-poor stars found there, and we lack the coverage of the abundance “spectrum” necessary to disentangle these relationships. To add more high-[α/Fe] populations to the sample of known exoplanets, we have been performing the Multiband Imaging Survey for High-Alpha PlanetS (MISHAPS). We use the Dark Energy Camera at Cerro Tololo Interamerican Observatory to search three high-[α/Fe] regions for hot Jupiters: the Galactic bulge, and the globular clusters 47 Tucanae and ω Centauri. This dissertation pri- marily presents the results of our study of 47 Tuc. Using 24 nights of observations, we search ~20,000 stars in the edges of the cluster for transit-like signals. Though we find no clear indications of planets, we are able to place a 0.43% upper limit on the occurrence rate of hot Jupiters in the cluster.
Date
7-27-2024
Recommended Citation
Crisp, Alison, "Constraining Giant Planet Occurrence Rates with the Multi-Band Imaging Survey for High-Alpha PlanetS (MISHAPS) Observations of 47 Tucanae" (2024). LSU Doctoral Dissertations. 6571.
https://repository.lsu.edu/gradschool_dissertations/6571
Committee Chair
Penny, Matthew