Deciphering the Complexity of Galaxy Structure

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Stone, Connor
Galaxies , Galaxy observations , Galaxy photometry , Galaxy scaling relations , Numerical methods , Spiral galaxies
This thesis presents the tools and findings in our investigation of galaxy structure. A first crucial endeavour consisted of assembling a uniform compendium of ``Photometry and Rotation curve Observations from Extragalactic Surveys'' (PROBES) of over 1500 late-type galaxies, the largest sample of its kind, for such investigations. Using PROBES, we were able to characterize the intrinsic properties of the Radial Acceleration Relation (RAR) in spiral galaxies, and verify their consistency with the Lambda Cold Dark Matter (CDM) cosmology and incompatibility with the previously proposed Modified Newtonian Dynamics (MOND) explanation. Further investigations in galaxy structure would require more extensive multi-band surface photometry processing capabilities; this was achieved by developing the AutoProf software. AutoProf can automatically and efficiently process galaxy images into non-parametric light profiles. It is typically more robust and achieves greater photometric depth than similar codes. Through this thesis work, the PROBES sample and AutoProf code were both released publicly and have already garnered significant attention. With the PROBES sample, an extensive investigation of the scatter of late-type galaxy scaling relations was also conducted. Our novel Bayesian technique enabled the determination of the intrinsic scatter of 36 scaling relations coupled with a most comprehensive comparison with the literature. The novel Bayesian intrinsic scatter technique revealed inadequacies in previous intrinsic scatter measurements, ultimately finding more diversity in galaxy populations than was previously appreciated. These findings, many of them novel, are instrumental for the development and fine-tuning of galaxy formation models.
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