The Fragmentation of Magnetized, Massive Star-Forming Cores with Radiative Feedback

TL;DR

This study uses advanced simulations to show that magnetic fields and radiative feedback together significantly reduce fragmentation in massive star-forming cores, favoring single star formation over clusters.

Contribution

It demonstrates that combined magnetic and radiative effects more effectively suppress core fragmentation than either process alone, explaining observed stellar mass distributions.

Findings

Magnetic fields and radiative feedback suppress fragmentation in massive cores.

Single star systems are likely from cores with typical mass-to-flux ratios.

A ~40 AU Keplerian disk can form despite magnetic braking.

Abstract

We present a set of 3-dimensional, radiation-magnetohydrodynamic calculations of the gravitational collapse of massive (300 Msun), star-forming molecular cloud cores. We show that the combined effects of magnetic fields and radiative feedback strongly suppress core fragmentation, leading to the production of single star systems rather than small clusters. We find that the two processes are efficient at suppressing fragmentation in different regimes, with the feedback most effective in the dense, central region and the magnetic field most effective in more diffuse, outer regions. Thus, the combination of the two is much more effective at suppressing fragmentation than either one considered in isolation. Our work suggests that typical massive cores, which have mass-to-flux ratios of about 2 relative to critical, likely form a single star system, but that cores with weaker fields may form a small star cluster. This result helps us understand why the observed relationship between the core mass function and the stellar initial mass function holds even for ~100 Msun cores with many thermal Jeans masses of material. We also demonstrate that a ~40 AU Keplerian disk is able to form in our simulations, despite the braking effect caused by the strong magnetic field.