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Title: Stellar spiral structures in realistic dark matter haloes
Author: Hu, Shaoran
ISNI:       0000 0004 6424 395X
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2017
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In this Thesis, I explore the formation and evolution of stellar spiral structures embedded in realistic dark matter haloes with very high resolution simulations. I first study the impact of the shape of the dark matter haloes. I find that non-adiabatic changes to the dark matter halo shape, commonly found in cosmological simulations due to the assembly history of haloes, can trigger strong two-armed grand-design spiral structures extending from the inner disc to the outer region. The nature of the spiral structures is found to be consistent with kinematic density waves based on the study of their power spectra. Such grand-design spiral structures may help the formation of transient multi-armed spiral structures if the self-gravity in disc is strong enough. Evolution of spiral structures is similar when the disc and the halo are misaligned, although warps develop additionally. I further find a strong correlation between the torque strength from the halo and the strength of the corresponding spiral structures. In the second part of my Thesis I then study the influence of subhaloes by including them from realistic cosmological simulations. I identify five different massive subhaloes that hit the central region of the disc, two out of which hit the disc twice. Aside from disc heating, three distinct generations of spiral structures are found in the stellar disc, which can be related to different subhaloes. For each generation, counter-rotating single-armed spiral structures develop first. They wind up very quickly before two-armed spiral structures become prominent. These spiral structures are again identified as kinematic density waves. We find that rather than interacting with the disc through resonances, subhaloes preferentially trigger spiral structures impulsively, due to their relatively short impact time with the disc. The strength of spiral structures can be related to the integrated strength of the torque generated by subhaloes. The correlation between the torque strength exerted by a triaxial dark matter halo and by subhaloes and the spiral strength may provide constraints on the distribution of dark matter.
Supervisor: Sijacki, Debora Sponsor: CSC-Cambridge Scholarship ; Lundgren Research Award
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: galaxy ; spiral structures ; dark matter halo ; numerical simulation