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The STUFF between the STARS - On the evolution of the interstellar medium in the real and simulated universe

Millard-Parry, Jenifer 2021. The STUFF between the STARS - On the evolution of the interstellar medium in the real and simulated universe. PhD Thesis, Cardiff University.
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In this Thesis, we perform a statistical study of the evolution of the interstellar content of galaxies over cosmic time, using both observational data and results from state-of-the-art cosmological hydrodynamical simulations. We first investigate the evolution of the gas mass fraction for galaxies in the COSMOS field using sub-millimetre emission from dust at 850um. Using stacking methodologies, we derive the gas mass fraction of high-mass galaxies (10^9.5 < M* < 10^11.75) out to high redshift (z<5), including more normal star-forming galaxies than previous studies. We find tentative evidence for a peak in the gas mass fraction of galaxies at around z ~ 2.5-3, just before the peak of the star formation history of the Universe. We find even at high redshifts, high stellar mass galaxies contain significant amounts of gas. Next, we use our stacked 850um fluxes to derive galaxy dust masses and develop a post-processing method to estimate dust masses of galaxies from the cosmological hydrodynamical simulation IllustrisTNG. We find that the observations show a strong evolution in the dust content of galaxies with cosmic time - galaxies were dustier in the past. In contrast, the evolution of dust content in the simulated galaxies is comparatively weak. The large discrepancy between observations and simulations plus post-processing may be explained by either strong cosmic evolution in the properties of dust grains, or limitations in the model, possibly connected to a lack of evolution in the neutral gas content of galaxies. We finish with a first-look estimate of the evolution of the comoving dust mass density with cosmic time, by combining stacked dust masses with previously published stellar mass functions of the COSMOS field to generate high-redshift (z<2.5) dust mass functions. In agreement with literature studies, we find a peak in the dust mass density at z ~ 1-1.8.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: interstellar medium, S2COSMOS, IllustrisTNG, astronomy, galaxies, dust, hydrogen, stacking, sub-millimetre, sub-mm, simulations, COSMOS, high redshift, astrophysics, SCUBA, SCUBA-2
Funders: European Research Council
Date of First Compliant Deposit: 21 April 2021
Last Modified: 21 Apr 2021 06:58

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