Probing galaxy evolution through numerical simulations: mergers, gas, and star formation

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dc.contributor.author Hani, Maan H.
dc.date.accessioned 2020-08-27T23:38:22Z
dc.date.available 2020-08-27T23:38:22Z
dc.date.copyright 2020 en_US
dc.date.issued 2020-08-27
dc.identifier.uri http://hdl.handle.net/1828/12035
dc.description.abstract Large observational surveys have compiled substantial galaxy samples with an array of different properties across cosmic time. While we have a broad understanding of how galaxies grow and build their observable properties, the details of galaxy growth and evolution pose a fundamental challenge to galaxy evolution theories. Nonetheless, galaxy evolution is ultimately regulated by the properties of the gas reservoir. In this thesis I use numerical simulations to answer key questions related to the galactic gas reservoir, and galaxy mergers: a major transformational process. In Chapter 2 I present an analysis of 28 simulated L* galaxies to understand the physical processes that shape the massive gas reservoir surrounding galaxies (i.e. the circum-galactic medium; CGM). I show that (1) the gas and metal content of the CGM is driven by galaxy growth and the strength/presence of feedback processes, and (2) the ionisation and internal structures of the CGM are shaped by galactic outflows, and active galactic nucleus luminosity. Albeit dependent on internal galactic properties and the physical processes that shape them, the CGM remains greatly diverse, thus posing a challenge for observational surveys. As a follow-up to my study of normal L* galaxy gas halos, in Chapter 3 I present a theoretical study of the effect of galaxy mergers on the CGM. I demonstrate that galaxy mergers can leave a strong imprint on the CGM's gas and metal content, metallicity, and size. The merger can increase (1) the CGM's metallicity by 0.2-0.3 dex within 0.5 Gyr post-merge, and (2) the metal covering fractions by factors of 2-3. In spite of the increase in the CGM's metal content, the hard ionising field during the merger can drive a decline in the covering fractions of commonly observed ions. In Chapter 4 I shift focus to star formation, particularly the effects of galaxy mergers on star formation. While the effects of galaxy mergers have been proven observationally, theoretical predictions are limited to small binary merger suites and cosmological zoom-in studies. I present a statistical study of 27,691 post-merger galaxies from IllustrisTNG to quantify the effect of galaxy mergers on galactic star formation. I report a dependence in the merger-induced star formation rate (SFR) on mass ratio, stellar mass, gas fraction, and galaxy SFR. I also track the evolution of the effects of galaxy mergers demonstrating their decay over ~500 Myr. In Chapter 6, I leverage galactic scaling relations to extend my work on the effects of galaxy mergers to resolved scales. However, before using the simulated resolved scaling relations, I first examine their existence and robustness. In Chapter 5, I demonstrate the emergence of the kpc-scale star forming main sequence (rSFMS) in the FIRE-2 simulations. Nonetheless, the slope of the rSFMS is dependent on the (1) star formation tracer's timescale, and (2) observed resolution, which I propose is caused by the clumpiness of star formation. I develop a toy model that quantitatively captures the effects of clumpy star formation. I then illustrate how the model can be used to characterise the mass of star-forming clumps. Having demonstrated the existence and robustness of known scaling relations in numerical simulations, I explore the effects of galaxy mergers on resolved scales in Chapter 6. I generate synthetic observations for 1,927 post-mergers in IllustrisTNG and examine the radially-dependent merger-driven SFR enhancement, and metallicity suppression in post-mergers. Galaxy mergers preferentially boost star formation in the centres and suppress metallicities globally. The effects of the merger depends on galaxy properties such as stellar mass, SFR, mass ratio, and gas fraction. en_US
dc.language English eng
dc.language.iso en en_US
dc.rights Available to the World Wide Web en_US
dc.subject galaxy evolution en_US
dc.subject numerical simulations en_US
dc.subject galaxy interactions en_US
dc.subject circumgalactic medium en_US
dc.subject Astronomy en_US
dc.subject Astrophysics en_US
dc.subject numerical hydrodynamics en_US
dc.subject galactic star formation en_US
dc.title Probing galaxy evolution through numerical simulations: mergers, gas, and star formation en_US
dc.type Thesis en_US
dc.contributor.supervisor Ellison, Sara L.
dc.degree.department Department of Physics and Astronomy en_US
dc.degree.level Doctor of Philosophy Ph.D. en_US
dc.identifier.bibliographicCitation Hani, M. H., Ellison, S. L., Sparre, M., Grand, R. J. J., Pakmor, R., Gomez, F. A., & Springel, V. (2019). The diversity of the circumgalactic medium around z = 0 milky way-mass galaxies from the auriga simulations. Monthly Notices of the Royal Astronomical Society, 488(1), 135-152. doi:10.1093/mnras/stz1708 en_US
dc.identifier.bibliographicCitation Hani, M., Sparre, M., Ellison, S., Torrey, P., & Vogelsberger, M. (2018). Galaxy mergers moulding the circum-galactic medium - I. the impact of a major merger. Monthly Notices of the Royal Astronomical Society, 475(1), 1160-1176. doi:10.1093/mnras/stx3252 en_US
dc.identifier.bibliographicCitation Hani, M., Gosain, H., Ellison, S., Patton, D., & Torrey, P. (2020). Interacting galaxies in the IllustrisTNG simulations II: Star formation in the post-merger stage. Monthly Notices of the Royal Astronomical Society, 493(3), 3716-3731. doi:10.1093/mnras/staa459 en_US
dc.identifier.bibliographicCitation Hani, M. H., Hayward, C. C., Orr, M. E., Ellison, S. L., Torrey, P., Murray, N., . . . Faucher-Giguère, C. (2020;2019;). Variations in the slope of the resolved star-forming main sequence: A tool for constraining the mass of star-forming regions. Monthly Notices of the Royal Astronomical Society. Letters, 493(1), L87-L91. doi:10.1093/mnrasl/slaa013 en_US
dc.description.scholarlevel Graduate en_US

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