Gaseous galactic haloes: The circumgalactic medium in cosmological simulations of different mass galaxies

Cook, Andrew 2024. Gaseous galactic haloes: The circumgalactic medium in cosmological simulations of different mass galaxies. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The circumgalactic medium (CGM) is the gaseous component of dark matter-dominated haloes that surrounds galaxies. It is responsible for the fuelling of star formation and acts as a reservoir for baryonic matter. The gas in the CGM is complex, spanning many orders of magnitude in temperature, density, metallicity and other key physical properties. Since its discovery in 1956, the CGM has been rigorously studied in observations and simulations of Milky Way-mass or more massive galaxies. However, it is difficult to constrain the CGM of dwarf galaxies as they are observationally challenging to study. The work enclosed in this thesis analyses halo simulations from the Auriga suite of magneto-hydrodynamical (MHD) cosmological zoom-in simulations, as well as extensions to the project that use the Auriga galaxy formation model. All of the simulations analysed in this thesis are created using the moving mesh code arepo. I have analysed 56 of these simulations, ranging in halo mass from 1010 M⊙−1013 M⊙ and mass resolutions of ~ 8 × 102 M⊙ - ~5.4 × 104 M⊙. The physical and observable properties of the CGM are studied to understand their dependence on halo mass in MHD simulations, how increasing the spatial refinement - decreasing the size of individual gas cells - of the simulations changes the CGM physical and observable properties and how MHD simulations compare to hydrodynamical simulations using the Auriga galaxy formation model to isolate how the inclusion of magneto-hydrodynamics affects the CGM. The results from these studies show that the physical and observable properties of the CGM are dependent on its halo mass and highlight that the numerical ranges of its properties are wider in more massive haloes. Furthermore, simulations which incorporate additional spatial refinement show more gas at cooler temperatures when compared to standard mass refinement simulations in 1012 M⊙ haloes but not in a 1011 M⊙ haloes. Finally, the CGM is sensitive to the presence of a magnetic field. The MHD simulations exhibit higher temperature, metallicity and column density at intermediate halo masses (1010.5 M⊙−1012.5 M⊙) compared to hydrodynamical simulations. It is clear from the findings of this thesis that the CGM is sensitive to halo mass, especially under different physical conditions (i.e. MHD or hydro simulations). However, these findings may be dependent on the specific models used in the Auriga galaxy formation model such as the interstellar medium model and the incorporation of feedback from supernovae and active galactic nuclei. It is therefore important that comparisons are made going forward between this work and future simulation or observation studies to better constrain our models, leading to better modelling for simulations.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Physics and Astronomy
Subjects:	Q Science > QC Physics
Uncontrolled Keywords:	circumgalactic medium, galaxies:haloes, methods:numerical, galaxies: evolution, hydrodynamics, MHD
Funders:	Cardiff University PSE College
Date of First Compliant Deposit:	31 January 2025
Last Modified:	31 Jan 2025 16:50
URI:	https://orca.cardiff.ac.uk/id/eprint/175795

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