Arepo public version

AREPO is a massively parallel code for gravitational n-body systems and hydrodynamics, both on Newtonian as well as cosmological background. It is a flexible code that can be applied to a variety of different types of simulations, offering a number of sophisticated simulation algorithms. An description of the numerical algorithms employed by the code is given in the original code papers (Springel 2010, MNRAS, 401, 791; Pakmor et al. 2011, MNRAS, 418, 1392; Pakmor and Springel 2013, MNRAS, 432, 176; Pakmor et al. 2016, MNRAS,455,1134) and the release paper of this version (Weinberger et al. 2019).

A user guide can be found under /documentation, which also includes a 'getting started' section, which is recommended for new users. An html version of the user guide can be created using sphinx (https://www.sphinx-doc.org) by typing

cd ./documentation/
make html

and displayed by opening ./documentation/build/html/index.html.

A full version of the user guide is also available on the Arepo homepage.

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This EOS Version (Master's Thesis 2024)

This version of AREPO attempted to extend the ISOTHERM_EQS flag to incorporate optional thermal evolution.

Key Features of the Attempt:

• Thermal Evolution Models: Introduced a SoundSpeedOption enum with the following options:

  • NO: Default behavior using a constant sound speed as per param.txt.
  • CONSTANT: Predefined constant values for sound speed.
  • LINEAR: Linearly evolving sound speed as a function of the scale factor.
  • POLYNOMIAL_PIECEWISE: Piecewise polynomial fit for sound speed evolution.

• Configuration: Configured in allvars.c for ease of modification. Default values/functions were derived from the CAMELS CV0 simulations.

• Implementation:

  • New files sound_speed.c and sound_speed.h implement the evolution logic.
  • Added getSoundSpeedIso function to compute sound speed based on the selected model.
  • Updated allvars.h to include the SoundSpeedOption enum.

Limitations: This approach faced challenges, including instability in cosmological volume simulations, particularly with negative density values. It became evident that the ISOTHERM_EQS flag in its original implementation was unsuitable for the project's scientific goals. This led to a reevaluation and subsequent developments in a more robust version.

For details on the revised model, visit to the second repository here.