SEREN – a new SPH code for star and planet formation simulations

Algorithms and tests^⋆

¹ Department of Physics and AstronomyUniversity of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, UK
e-mail: D.Hubber@sheffield.ac.uk
² School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff, CF24 3AA, Wales, UK
³ Institute for Theoretical Astrophysics, University of Oslo, Pb 1029 Blindern, 0315 Oslo, Norway
⁴ Centre of Mathematics for Applications, University of Oslo, Pb 1053 Blindern, 0316 Oslo, Norway
⁵ Astronomical Institute, Academy of Sciences of the Czech Republic, Boční II 1401, 141 31 Praha 4, Czech Republic

Received: 6 May 2010
Accepted: 29 January 2011

Abstract

We present SEREN, a new hybrid Smoothed Particle Hydrodynamics and N-body code designed to simulate astrophysical processes such as star and planet formation. It is written in Fortran 95/2003 and has been parallelised using OpenMP. SEREN is designed in a flexible, modular style, thereby allowing a large number of options to be selected or disabled easily and without compromising performance. SEREN uses the conservative “grad-h” formulation of SPH, but can easily be configured to use traditional SPH or Godunov SPH. Thermal physics is treated either with a barotropic equation of state, or by solving the energy equation and modelling the transport of cooling radiation. A Barnes-Hut tree is used to obtain neighbour lists and compute gravitational accelerations efficiently, and an hierarchical time-stepping scheme is used to reduce the number of computations per timestep. Dense gravitationally bound objects are replaced by sink particles, to allow the simulation to be evolved longer, and to facilitate the identification of protostars and the compilation of stellar and binary properties. At the termination of a hydrodynamical simulation, SEREN has the option of switching to a pure N-body simulation, using a 4th-order Hermite integrator, and following the ballistic evolution of the sink particles (e.g. to determine the final binary statistics once a star cluster has relaxed). We describe in detail all the algorithms implemented in SEREN and we present the results of a suite of tests designed to demonstrate the fidelity of SEREN and its performance and scalability.