The cosmic web in the Laduma field

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dc.contributor.advisorBlyth, Sarah-Louise
dc.contributor.advisorSkelton, Rosalind
dc.contributor.authorOelgeschlager, Tilman
dc.date.accessioned2025-09-18T13:18:01Z
dc.date.available2025-09-18T13:18:01Z
dc.date.issued2025
dc.date.updated2025-09-18T13:08:39Z
dc.description.abstractCosmic web filaments are an intermediate density environment that have been shown to play a role in the evolution of galaxies. In order to accurately identify cosmic web filaments in a volume, a complete sample of galaxies with accurate distance measurements is required. For this reason, studies which identify filaments and investigate the properties of galaxies within them have been mostly restricted to the local Universe, where complete samples of galaxies with spectroscopic redshift measurements are available. In this thesis, I investigate filaments in the cosmic volume targeted by the Looking at the Distant Universe with the MeerKAT Array (LADUMA) survey at higher redshifts. LADUMA's ancillary data catalogue provides a limited sample of spectroscopic redshift measurements across LADUMA's target volume. I use the DisPerSE software package to identify large-scale structures. I use the Simba cosmological simulation to investigate the impact of using such a spectroscopic redshift catalogue on the output of DisPerSE. In particular, I test the effect of redshift-space distortions and their correction, incompleteness, sample bias and varying completeness on the accuracy of the large-scale structure found by DisPerSE. I find that the incompleteness of the LADUMA galaxy sample is the dominant cause of inaccuracy in the identified filament network. I test a method of improving the accuracy of the output of DisPerSE using photometric redshift measurements in the Simba simulation. I find that implementing this method with the photometric redshift measurements currently available in the LADUMA volume will not result in a more accurate filament network. Taking the simulation results into account, I use DisPerSE to create a map of filaments in the LADUMA target field using spectroscopic redshifts in the redshift range 0.2 < z < 0.4. Upon investigation, I find that galaxies in the LADUMA volume close to filaments have higher stellar masses and lower specific star formation rates compared to galaxies far from filaments. I find the same trends for galaxies and filaments in the Simba simulation volume. The increase in the stellar mass of galaxies toward filaments is found to be the primary driver for the corresponding decrease in specific star formation rate in both simulations and observations.
dc.identifier.apacitationOelgeschlager, T. (2025). <i>The cosmic web in the Laduma field</i>. (). University of Cape Town ,Faculty of Science ,Department of Astronomy. Retrieved from http://hdl.handle.net/11427/41867en_ZA
dc.identifier.chicagocitationOelgeschlager, Tilman. <i>"The cosmic web in the Laduma field."</i> ., University of Cape Town ,Faculty of Science ,Department of Astronomy, 2025. http://hdl.handle.net/11427/41867en_ZA
dc.identifier.citationOelgeschlager, T. 2025. The cosmic web in the Laduma field. . University of Cape Town ,Faculty of Science ,Department of Astronomy. http://hdl.handle.net/11427/41867en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Oelgeschlager, Tilman AB - Cosmic web filaments are an intermediate density environment that have been shown to play a role in the evolution of galaxies. In order to accurately identify cosmic web filaments in a volume, a complete sample of galaxies with accurate distance measurements is required. For this reason, studies which identify filaments and investigate the properties of galaxies within them have been mostly restricted to the local Universe, where complete samples of galaxies with spectroscopic redshift measurements are available. In this thesis, I investigate filaments in the cosmic volume targeted by the Looking at the Distant Universe with the MeerKAT Array (LADUMA) survey at higher redshifts. LADUMA's ancillary data catalogue provides a limited sample of spectroscopic redshift measurements across LADUMA's target volume. I use the DisPerSE software package to identify large-scale structures. I use the Simba cosmological simulation to investigate the impact of using such a spectroscopic redshift catalogue on the output of DisPerSE. In particular, I test the effect of redshift-space distortions and their correction, incompleteness, sample bias and varying completeness on the accuracy of the large-scale structure found by DisPerSE. I find that the incompleteness of the LADUMA galaxy sample is the dominant cause of inaccuracy in the identified filament network. I test a method of improving the accuracy of the output of DisPerSE using photometric redshift measurements in the Simba simulation. I find that implementing this method with the photometric redshift measurements currently available in the LADUMA volume will not result in a more accurate filament network. Taking the simulation results into account, I use DisPerSE to create a map of filaments in the LADUMA target field using spectroscopic redshifts in the redshift range 0.2 < z < 0.4. Upon investigation, I find that galaxies in the LADUMA volume close to filaments have higher stellar masses and lower specific star formation rates compared to galaxies far from filaments. I find the same trends for galaxies and filaments in the Simba simulation volume. The increase in the stellar mass of galaxies toward filaments is found to be the primary driver for the corresponding decrease in specific star formation rate in both simulations and observations. DA - 2025 DB - OpenUCT DP - University of Cape Town KW - Cosmic web LK - https://open.uct.ac.za PB - University of Cape Town PY - 2025 T1 - The cosmic web in the Laduma field TI - The cosmic web in the Laduma field UR - http://hdl.handle.net/11427/41867 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/41867
dc.identifier.vancouvercitationOelgeschlager T. The cosmic web in the Laduma field. []. University of Cape Town ,Faculty of Science ,Department of Astronomy, 2025 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/41867en_ZA
dc.language.isoen
dc.language.rfc3066eng
dc.publisher.departmentDepartment of Astronomy
dc.publisher.facultyFaculty of Science
dc.publisher.institutionUniversity of Cape Town
dc.subjectCosmic web
dc.titleThe cosmic web in the Laduma field
dc.typeThesis / Dissertation
dc.type.qualificationlevelMasters
dc.type.qualificationlevelMSc
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