Erratum: Collapse of a molecular cloud core to stellar densities: Stellar core and outflow formation in radiation magnetohydrodynamics simulations [MNRAS, 465, (2017) (2714-2716)] DOI: 10.1093/mnras/stt1865

Abstract

The paper 'Collapse of a molecular cloud core to stellar densities: stellar core and outflow formation in radiation magnetohydrodynamics simulations' was published in MNRAS, 437, 77 (2014) (hereafter 'the Original Paper'). The calculations presented in that work were performed using a smoothed particle magnetohydrodynamics code known as sphNG. Unfortunately, a bug was present in the integrator that was used to evolve the magnetic field. This necessitated the use of rapid divergence cleaning of the magnetic field (using a cleaning speed 30 times faster than the fast magnetohydrodynamics, MHD, wave speed) in the Original Paper in order to maintain stability of the calculations.We are grateful to Dobbs (private communication) for the discovery of the error in the integrator. In this erratum, we compare results from one of the original calculations with those obtained using a more recent version of the code in which the integrator has been corrected. In addition, the more recent code includes the improved divergence cleaning scheme of Tricco, Price & Bate (2016), though we have found that for this problem, the differences between calculations using the older cleaning scheme and those using the new scheme are insignificant. The corrected code uses the standard divergence cleaning wave speed (equal to the fast MHD wave speed). This allows larger timesteps to be taken, which results in the calculations running up to 30 times faster early on. However, after the stellar core forms, the calculations are only about four times faster because thermal and gravitational forces dominate over magnetic forces inside the stellar core.We show that the results of the calculations are slightly different, but these minor differences do not affect the conclusions in the Original Paper. Section 1 of this erratum discusses the integrator bug in detail and then in Section 2, we provide a side-by-side comparison of the calculation from the Original Paper that had the strongest magnetic field strength with a calculation using the more recent code that uses a corrected integrator and includes the improved divergence cleaning scheme.