Rahimi, A; (2012) Chemodynamical simulations of disc galaxies. Doctoral thesis , UCL (University College London).

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Abstract

We use numerical simulations to probe the evolutionary history of spiral galaxies such as our own Milky Way. We use the chemodynamical simulation code GCD+ to simulate several galaxies both in a cosmological and isolated environment. The simulations include gravity, hydrodynamics, radiative gas cooling, star formation, stellar evolution, metal production and feedback into the interstellar medium. We describe in detail how these physical processes are implemented in two different versions of the code adopted in this thesis. The simulations are compared with observations in order to disentangle the details of spiral galaxy formation. Several unresolved issues regarding the evolution of spiral galaxies are specifically addressed. We first analyse the properties of stars found in the bulge component of our simulated spiral galaxies, finding that stars formed during mergers at different epochs show different elemental abundance ratio [α/Fe]. Stars formed during one of the merger events retain a systematically prograde rotation at the present time demonstrating that ancient orbital information may still be preserved in the present day kinematics of bulge stars. Next, we analysed the radial abundance gradients along the disc, comparing with recent observations from the Milky Way. We found that the disc contains a greater fraction of young stars in the outer regions, with older stars in the inner regions. This could explain the positive [α/Fe] and negative [N/O] gradients with radius. These radial trends are a natural outcome of an inside-out formation of the disc and could thus explain the recently observed positive [α/Fe] gradients seen in Milky Way disc open clusters. Finally, several isolated galaxy evolution simulations were carried out using the new and improved version of our N-body/smoothed particle hydrodynamics code. We show that our models with higher energy feedback from supernovae and stellar winds more closely resemble the observations of spiral galaxies.

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