The evolution of galaxies : starbursts and beyond

Wilkinson, Charlotte Louise

Abstract

Determining how galaxies evolve and what drives their evolution is one of the biggest challenges in astronomy. This thesis aims to shed light on the life-cycle of galaxies by answering the following questions: (1) How do different selection methods of post-starburst galaxies have an impact on the properties observed? (2) What are the main triggers of starburst, and hence, the post-starburst galaxies in the Illustris simulation? (3) Do starburst galaxies have a top-heavy IMF and produce heavier stars than quiescently star forming galaxies? (4) To what extent do AGN play a role in quenching star formation in starburst galaxies which lead to the post-starburst phase? For question one, we investigate the effect of different selection criteria of post-starburst galaxies, we reveal an evolutionary sequence that transitions from the blue cloud through the green valley before settling in the red sequence. We find a lack of any significant merger fractions which suggests that secular processes or minor mergers/interactions may play an important role in triggering starburst as opposed to major mergers. For question two, we investigate the triggering mechanisms of starbursts and find that over half of our starburst sample have not undergone a recent merger but have instead experienced harassment. Harassment triggered starbursts are comparable in strength to merger driven starbursts and are found in denser environments, suggesting environment plays a role in determining the processes that trigger a burst. For questions three and four, we compare optical and radio emission to determine the formof the IMF and to detect the presence of AGN in starbursts. We find that starbursts show some evidence for a top-heavy IMF, however no significant AGN fraction, suggesting other processes, such as stellar winds, quench starbursts or the overlap time between starburst and AGN phases is very small and therefore starbursts with AGN are extremely rare.

Citation

Wilkinson, C. L. (2018). The evolution of galaxies : starbursts and beyond. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4221716

• Thesis Type: Thesis
• Deposit Date: Aug 2, 2019
• Publicly Available Date: Feb 23, 2023
• Keywords: Physics
• Public URL: https://hull-repository.worktribe.com/output/4221716
• Additional Information: Department of Physics, The University of Hull
• Award Date: Oct 1, 2018