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Cosmological Simulations with TreeSPH
Neal Katz
University of Washington, Department of Astronomy, Seattle, WA 98195
David H. Weinberg
Ohio State University, Department of Astronomy, Columbus, OH 43210
Also, Institute for Advanced Study, Princeton, NJ 08540
Lars Hernquist
Sloan Fellow, Presidential Faculty Fellow
University of California, Lick Observatory, Santa Cruz, CA 95064
E-mail: nsk@astro.washington.edu, dhw@payne.mps.ohio-state.edu,
lars@ucolick.edu
Abstract:
We describe numerical methods for incorporating gas dynamics into
cosmological simulations and present illustrative applications
to the cold dark matter (CDM) scenario.
Our evolution code, a version of TreeSPH (Hernquist & Katz 1989)
generalized to handle
comoving coordinates and periodic boundary conditions,
combines smoothed--particle hydrodynamics (SPH) with the hierarchical
tree method for computing gravitational forces.
The Lagrangian hydrodynamics approach and individual
time steps for gas particles give the algorithm a large dynamic range,
which is
essential for studies of galaxy formation in a cosmological context.
The code incorporates radiative cooling for an optically thin,
primordial composition gas in ionization equilibrium with a
user-specified ultraviolet background. We adopt a phenomenological
prescription for star formation that gradually turns cold, dense,
Jeans-unstable gas into collisionless stars, returning supernova
feedback energy to the surrounding medium.
In CDM simulations, some of the baryons that fall into dark matter
potential wells dissipate their acquired thermal energy and
condense into clumps with roughly galactic masses.
The resulting galaxy population
is insensitive to assumptions about star formation;
we obtain similar baryonic mass functions and galaxy correlation
functions from simulations with star formation and from simulations
without star formation in which we identify galaxies directly from
the cold, dense gas.
Methods: numerical, Hydrodynamics, Galaxies:formation, large-scale
structure of Universe
