Universiteit Leiden

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Dissertation

Monsters in the Deep: Using simulations to understand the excess baryonic mass in the centres of high-mass, early-type galaxies

This thesis aims to enhance our understanding of galaxies by testing theoretical models of galaxy formation against observations, particularly in the cases of extreme systems which have been found to have an excess of baryonic mass in their central regions, in the form of either supermassive black holes or stellar populations, thus harbouring "monsters" in the deep.

Author
Barber, C.R.
Date
20 November 2018
Links
Thesis in Leiden Repository

This thesis aims to enhance our understanding of galaxies by testing theoretical models of galaxy formation against observations, particularly in the cases of extreme systems which have been found to have an excess of baryonic mass in their central regions, in the form of either supermassive black holes or stellar populations, thus harbouring "monsters" in the deep. To this end we use the EAGLE project, a suite of cosmological, hydrodynamical simulations of galaxy formation and evolution that have been calibrated to reproduce the number density and sizes of galaxies in the Universe. We find that galaxies with supermassive black holes that are much more massive than expected given their stellar mass are predicted to exist and they become overmassive through early formation and/or tidal stripping from more massive galaxies. Recent evidence for excess stellar mass in the centres of high-mass, early-type galaxies has fueled claims that the stellar initial mass function (IMF) may be variable. We test the consequences of such variations in the EAGLE model by performing two additional simulations in which the IMF becomes respectively top-heavy or bottom-heavy in high-pressure environments. The strong effects of such variations are explored in terms of scaling relations between, and within, galaxies.

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