1,065 research outputs found
A Superbubble Feedback Model for Galaxy Simulations
We present a new stellar feedback model that reproduces superbubbles.
Superbubbles from clustered young stars evolve quite differently to individual
supernovae and are substantially more efficient at generating gas motions. The
essential new components of the model are thermal conduction, sub-grid
evaporation and a sub-grid multi-phase treatment for cases where the simulation
mass resolution is insufficient to model the early stages of the superbubble.
The multi-phase stage is short compared to superbubble lifetimes. Thermal
conduction physically regulates the hot gas mass without requiring a free
parameter. Accurately following the hot component naturally avoids overcooling.
Prior approaches tend to heat too much mass, leaving the hot ISM below K
and susceptible to rapid cooling unless ad-hoc fixes were used. The hot phase
also allows feedback energy to correctly accumulate from multiple, clustered
sources, including stellar winds and supernovae.
We employ high-resolution simulations of a single star cluster to show the
model is insensitive to numerical resolution, unresolved ISM structure and
suppression of conduction by magnetic fields. We also simulate a Milky Way
analog and a dwarf galaxy. Both galaxies show regulated star formation and
produce strong outflows.Comment: 13 pages, 13 figures; replaced with version accepted to MNRA
Simulation of primordial object formation
We have included the chemical rate network responsible for the formation of
molecular Hydrogen in the N-body hydrodynamic code, Hydra, in order to study
the formation of the first cosmological at redshifts between 10 and 50. We have
tested our implementation of the chemical and cooling processes by comparing
N-body top hat simulations with theoretical predictions from a semi-analytic
model and found them to be in good agreement. We find that post-virialization
properties are insensitive to the initial abundance of molecular hydrogen. Our
main objective was to determine the minimum mass () of perturbations
that could become self gravitating (a prerequisite for star formation), and the
redshift at which this occurred. We have developed a robust indicator for
detecting the presence of a self-gravitating cloud in our simulations and find
that we can do so with a baryonic particle mass-resolution of 40 solar masses.
We have performed cosmological simulations of primordial objects and find that
the object's mass and redshift at which they become self gravitating agree well
with the results from the top hat simulations. Once a critical
molecular hydrogen fractional abundance of about 0.0005 has formed in an
object, the cooling time drops below the dynamical time at the centre of the
cloud and the gas free falls in the dark matter potential wells, becoming self
gravitating a dynamical time later.Comment: 45 pages, 17 figures, submitted to Ap
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