Implementation of Sink Particles in the Athena Code

TL;DR

This paper details the implementation and validation of sink particles in the Athena code, enabling long-term simulations of collapsing systems by modeling accretion and gravitational interactions.

Contribution

It introduces a new sink particle algorithm in Athena, with criteria based on Larson-Penston collapse, and demonstrates its effectiveness through various tests and turbulent flow simulations.

Findings

Validated sink particle implementation against analytic solutions

Successfully simulated core formation and collapse in turbulent flow

Demonstrated long-term evolution of systems with sink interactions

Abstract

We describe implementation and tests of sink particle algorithms in the Eulerian grid-based code Athena. Introduction of sink particles enables long-term evolution of systems in which localized collapse occurs, and it is impractical (or unnecessary) to resolve the accretion shocks at the centers of collapsing regions. We discuss similarities and differences of our methods compared to other implementations of sink particles. Our criteria for sink creation are motivated by the properties of the Larson-Penston collapse solution. We use standard particle-mesh methods to compute particle and gas gravity together. Accretion of mass and momenta onto sinks is computed using fluxes returned by the Riemann solver. A series of tests based on previous analytic and numerical collapse solutions is used to validate our method and implementation. We demonstrate use of our code for applications with a simulation of planar converging supersonic turbulent flow, in which multiple cores form and collapse to create sinks; these sinks continue to interact and accrete from their surroundings over several Myr.