Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Shark: introducing an open source, free and flexible semi-analytic model
  of galaxy formation   We present a new, open source, free semi-analytic model (SAM) of galaxy
formation, Shark, designed to be highly flexible and modular, allowing easy
exploration of different physical processes and ways of modelling them. We
introduce the philosophy behind Shark and provide an overview of the physical
processes included in the model. Shark is written in C++11 and has been
parallelized with OpenMP. In the released version (v1.1), we implement several
different models for gas cooling, active galactic nuclei, stellar and
photo-ionisation feedback, and star formation (SF). We demonstrate the basic
performance of Shark using the Planck15 cosmology SURFS simulations, by
comparing against a large set of observations, including: the stellar mass
function (SMF) and stellar-halo mass relation at z=0-4; the cosmic evolution of
the star formation rate density (SFRD), stellar mass, atomic and molecular
hydrogen; local gas scaling relations; and structural galaxy properties,
finding excellent agreement. Significant improvements over previous SAMs are
seen in the mass-size relation for disks/bulges, the gas-stellar mass and
stellar mass-metallicity relations. To illustrate the power of Shark in
exploring the systematic effects of the galaxy formation modelling, we quantify
how the scatter of the SF main sequence and the gas scaling relations changes
with the adopted SF law, and the effect of the starbursts H$_2$ depletion
timescale on the SFRD and $\Omega_{\rm H_2}$. We compare Shark with other SAMs
and the hydrodynamical simulation EAGLE, and find that SAMs have a much higher
halo baryon fractions due to large amounts of intra-halo gas, which in the case
of EAGLE is in the intergalactic medium.

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The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: math
9
The categories of this paper are: nlin
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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
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The categories of this paper are: cond-mat
1
The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: physics
32
The categories of this paper are: atom-ph