Cold Gas Accretion in a Magnetised Circum-Galactic Medium

Kooij, Richard (2020) Cold Gas Accretion in a Magnetised Circum-Galactic Medium. Master's Thesis / Essay, Astronomy.

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Abstract

Observations show the presence of "cold" ($\sim10^4$ K) gas around galaxies that is often in- or out-flowing at speeds on the order of 100 km/s. This cold gas co-exists with hot ($\sim10^6$ K) galactic halos creating a complex, multi-phase circum-galactic medium. This circumgalactic medium is likely the source of gas accretion onto disc galaxies and thus the reservoir for star formation. Studying the interactions of cold gas with a hot galactic halo is thus vital to further understand galaxy formation and evolution. In this work we investigate the effects of thermal conduction by comparing the evolution of 3D hydrodynamical (HD) simulations using artificially suppressed isotropic thermal conduction with $f$, against 3D magneto-hydrodynamical (MHD) simulations with (true) anisotropic thermal conduction. We explore different strengths and orientations of the magnetic field, different densities and metallicities of the media and different relative velocities between the cloud and the hot gas. Our main diagnostic is the evolution of the amount of cold gas as a function of time in the simulation domain. We found that in almost every HD and MHD run, the amount of cold gas increases with time, indicating that hot gas condensation is an important phenomenon that can contribute to gas accretion onto galaxies. When the magnetic field is oriented transverse to the cloud velocity, a configuration that we consider most realistic, we find that $f$ is in the range $0.03-0.15$.

Item Type:	Thesis (Master's Thesis / Essay)
Supervisor name:	Fraternali, F.
Degree programme:	Astronomy
Thesis type:	Master's Thesis / Essay
Language:	English
Date Deposited:	28 Jul 2020 12:30
Last Modified:	28 Jul 2020 12:30
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/22896

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