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The Dark Matter Problem in Rotationally Supported Galaxies

Li, Pengfei
http://orcid.org/0000-0002-6707-2581
http://rave.ohiolink.edu/etdc/view?acc_num=case159440473976029

Abstract Details

2020, Doctor of Philosophy, Case Western Reserve University, Astronomy.
Different lines of evidence suggest that the observed dynamics of galaxies, galaxy clusters, and the Universe as a whole cannot be explained by the visible, baryonic matter when applying the standard laws of Gravity. Two competing solutions have been proposed and hotly debated in the past decades: introduce dark matter (DM) or modify the laws of gravity. In this dissertation, I present a systematic investigation of these two hypothesis using 175 late-type galaxies from the Spitzer Photometry \& Accurate Rotation Curves (SPARC) database. On the DM front, I fit the SPARC rotation curves testing seven different halo profiles. Based on these fits, I explore the correlations between DM halos and stellar disks, and find that the characteristic volume density of DM halos is remarkably constant over 5 decades in galaxy luminosity. This serves as a testing bed for galaxy formation models. Using the correlation between DM halo masses and \hi\ line widths, I measure for the first time the DM halo mass function (HMF). The measured HMF agrees with the prediction of DM-only simulations at intermediate and low halo masses, but differs significantly at high mass end. Finally I compute the effect of adiabatic compression on the DM halos due to the baryonic gravitational potential, and find that compressed halos contribute more to rotation curves, exacerbating the core-cusp problem over the whole range of galaxy masses. On the modified gravity front, I test the statistically established radial acceleration relation (RAR) which indicates a strong link between the baryonic mass distribution and the observed dynamics of galaxies. The vast majority of the SPARC galaxies can be well described by the RAR. The best-fit RAR has an rms scatter of 0.057 dex, comparable to the observational uncertainties on rotation curves. This leaves little room for intrinsic scatter if any. I check the critical acceleration scale in the RAR is universal among late-type galaxies, marking no difference between the RAR and the Modified Newtonian Dynamics. Overally, Modified Newtonian Dynamics can describe disk galaxies with less problems than DM models, but a comprehensive evaluation requires the systematic investigations on galaxy-cluster and cosmological scales.
Stacy McGaugh (Committee Chair)
Federico Lelli (Committee Member)
Earle Luck (Committee Member)
Christopher Mihos (Committee Member)
Benjamin Monreal (Committee Member)
162 p.
Astronomy; Astrophysics

Recommended Citations

Citations

  • Li, P. (2020). The Dark Matter Problem in Rotationally Supported Galaxies [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case159440473976029

    APA Style (7th edition)

  • Li, Pengfei. The Dark Matter Problem in Rotationally Supported Galaxies. 2020. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case159440473976029.

    MLA Style (8th edition)

  • Li, Pengfei. "The Dark Matter Problem in Rotationally Supported Galaxies." Doctoral dissertation, Case Western Reserve University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case159440473976029

    Chicago Manual of Style (17th edition)

case159440473976029
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This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.
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