In this thesis, we present a novel algorithm for computing the radiation field in
astrophysical simulations. The algorithm is tree-based, similar to many gravity
solvers, and allows computation of radiative transfer in O(Nsink logNsource) in
cases without absorption, and O(Nsink logNsource logN) time with absorption.
The algorithm scales well with the number of processors due to its tree-based
nature, and is highly tunable in accuracy and speed. It is also only weakly
dependent on both the energy band and the number of energy bands used.
We provide a suite of tests of the code showing its ability to create accurate
fluxes, ionization fronts, hydrodynamics coupling, and shadowing.
We apply the algorithm in a set of simulations on an isolated spiral
galaxy from the AGORA project. The algorithm is used to calculate FUV
fields within the galaxy, which self-consistently sets the dominant photoelectric
heating in the gas. This has never before been performed in galaxy simulations.
We find, in agreement with Ostriker et al. [2010], that FUV can be a very
important regulation mechanism for star formation in a galaxy. Depending
on the assumed opacity, FUV can decrease the average star formation rate
(SFR) anywhere from 15% to a factor of twenty. We compare this regulation
mechanism to a highly effective model of supernovae (SNe) feedback, which
reduces the SFR by a factor of twenty as well. However, SNe feedback destroys
most of the gas structure in the process, whereas FUV has minimal impact on
the gas structure.
In the simulations with FUV radiation, we are also able to create a two
phase medium that is a function of the mean FUV intensity the gas receives.
Finally, we find that simulations with FUV agree well with observations of
nearby spirals on the Kennicutt-Schmidt relation, at least at gas surface densities
of 0.2 - 30 M⊙. At surface densities higher than 30 M⊙, we find that
FUV is not an effective regulator which is consistent with arguments that SNe
or other feedback mechanisms should become the primary regulator. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/18234 |
| Date | 20 November 2015 |
| Creators | Woods, Rory |
| Contributors | Wadsley, James, Couchman, Hugh, Physics and Astronomy |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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