Magnetic fields and Turbulence in Star Formation using Smoothed Particle Hydrodynamics

TL;DR

This paper reviews the integration of magnetic fields into Smoothed Particle Hydrodynamics for star formation, compares simulation techniques, and explores turbulence density relations, highlighting current limitations and new findings.

Contribution

It provides a comprehensive overview of MHD-SPH methods, compares SPH and Eulerian turbulence simulations, and presents novel results on density variance and Mach number relationships.

Findings

SPH and Eulerian turbulence simulations show consistent results at high Mach numbers.

The density variance-Mach number relation is sigma^2_{ln rho} = ln(1 + b^2 M^2) with b=0.33.

Observational data in Taurus and IC5146 do not match the simulation-based relation.

Abstract

Firstly, we give a historical overview of attempts to incorporate magnetic fields into the Smoothed Particle Hydrodynamics method by solving the equations of Magnetohydrodynamics (MHD), leading an honest assessment of the current state-of-the-art in terms of the limitations to performing realistic calculations of the star formation process. Secondly, we discuss the results of a recent comparison we have performed on simulations of driven, supersonic turbulence with SPH and Eulerian techniques. Finally we present some new results on the relationship between the density variance and the Mach number in supersonic turbulent flows, finding sigma^2_{ln rho} = ln (1 + b^2 M^2) with b=0.33 up to Mach~20, consistent with other numerical results at lower Mach number (Lemaster and Stone 2008) but inconsistent with observational constraints on sigma_rho and M in Taurus and IC5146.