Date of Award

Fall 12-2022

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

Advisor

David J. Batuski

Second Committee Member

Neil Comins

Third Committee Member

Charles Hess

Additional Committee Members

Andre Khalil

James McClymer

Abstract

Observations of the Universe on very large scales have shown it to be filled with galaxy clusters and superclusters connected by walls and filaments of galaxies, with vast areas mostly devoid of luminous matter separating them. It is widely accepted that the amount of luminous matter does not provide the mass needed to hold galaxies and galaxy clusters together, and the nature of the missing "dark matter" is one of the most prominent astrophysical mysteries today. Since dark matter interacts with luminous matter gravitationally, it stands to reason that dark matter might organize itself in a similar manner to luminous matter, forming clumps and voids with filaments connecting them, but while there have been simulations showing that this is likely true, the observational efforts looking for dark matter filaments have been few and contradictory.

I present a weak gravitational lensing analysis of two particularly overdense galaxy superclusters, The Aquarius Supercluster (ASC) and the Microscopium Supercluster (MSC), in order to probe the mass distribution in these regions. Observations were performed on the DECam mounted on the Victor Blanco 4-m Telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. The image data was processed by the DECam Pipeline and then reduced with Source Extractor software. The images were broken into data broken into grid of varying mesh sizes, and two different maps of lensing were created for each mesh size, with one being weighted by the frequency of objects with a given orientation, and the other weighted by the ellipticities of the objects with a given orientation. In order to interpret the lensing maps, model maps of the expected gravitational shear from the superclusters were created for comparison. The results show that the data matches the model much better for the MSC than the ASC. With a confidence level of 1-3σ for the majority of maps, it seems likely that we are detecting at least some weak gravitational lensing for the ASC. The higher levels of 1-8σ for the maps of the MSC region are strong evidence of gravitational lensing in this field. The difference between the two regions is suspected to be likely an effect of other clusters in the field of view. While the sky offers a fairly clean view of the MSC with only a couple of identified background clusters, the ASC region is cluttered with various other clusters. The results neither confirm nor preclude the existence of a filamentary structure of inter-cluster matter, but do suggest that any such filaments would likely be significantly less massive than the clusters themselves, which appear to dominate the region

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