Cosmological simulations of the effects of primordial molecules on the first generation of stars
Date
2018
Authors
Unterslak, Matthew James
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Abstract
In this study I present new results based on the implementation of molecular cooling
and primordial streaming velocities into the hydro-dynamical simulation code
GASOLINE. I demonstrate that the inclusion of molecular cooling as a cooling branch
in the primordial gas and the addition of a homogeneous streaming velocity in the
initial velocity field, are both critical to the study of Pop III stars. Pop III stars have a
profound impact on galaxy formation, completely altering the chemical composition
and thermal evolution of the gas. Future observations with the SKA telescope are
expected to reveal some of the signatures of primordial star formation and thus enable
the comparison with the numerical predictions. Numerical simulations employed
to model the evolution of the primordial gas are able to capture the dynamics wellenough
to predict the formation times of Pop III stars. The present study confirms
that H2 and HD are the most dominant coolants at high redshifts. The implementation
of a homogeneous streaming velocity field, generated by the decoupling of gas
and DM at the epoch of decoupling (z ~ 1100), delays the collapse of the gas at the
centre of the DM haloes and thus delays Pop III star formation. The overall result of
the implementation of molecular cooling and primordial streaming velocities is that
they compensate each other to a certain degree, such that the formation times of the
first stars remain roughly unchanged - accelerated by the inclusion of molecules and
decelerated as a consequence of the primordial streaming velocities, but it is unclear
whether these effects exactly compensate one another.
Description
A dissertation submitted in fulfillment of the requirements
for the degree of Master of Science
in the Astrophysics Group School of Physics, Johannesburg, April 29, 2018.
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Citation
Unterslak, Matthew James, (2018) Cosmological simulations of the effects of primordial molecules on the first generation of stars, University of the Witwatersrand, Johannesburg, https://hdl.handle.net/10539/25835.