Abstract
Using an isolated Milky Way-mass galaxy simulation, we compare results from 9
state-of-the-art gravito-hydrodynamics codes widely used in the numerical
community. We utilize the infrastructure we have built for the AGORA
High-resolution Galaxy Simulations Comparison Project. This includes the common
disk initial conditions, common physics models (e.g., radiative cooling and UV
background by the standardized package Grackle) and common analysis toolkit yt,
all of which are publicly available. Subgrid physics models such as Jeans
pressure floor, star formation, supernova feedback energy, and metal production
are carefully constrained across code platforms. With numerical accuracy that
resolves the disk scale height, we find that the codes overall agree well with
one another in many dimensions including: gas and stellar surface densities,
rotation curves, velocity dispersions, density and temperature distribution
functions, disk vertical heights, stellar clumps, star formation rates, and
Kennicutt-Schmidt relations. Quantities such as velocity dispersions are very
robust (agreement within a few tens of percent at all radii) while measures
like newly-formed stellar clump mass functions show more significant variation
(difference by up to a factor of ~3). Intrinsic code differences such as
between mesh-based and particle-based codes are small, and are generally
dwarfed by variations in the numerical implementation of the common subgrid
physics. Our experiment reassures that, if adequately designed in accordance
with our proposed common parameters, results of a modern high-resolution galaxy
formation simulation are more sensitive to input physics than to intrinsic
differences in numerical schemes. We also stress the importance of
collaborative and reproducible research in the numerical galaxy formation
community the AGORA Project strives to promote.
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