Limiting Accretion onto Massive Stars by Fragmentation-Induced Starvation

TL;DR

This paper uses simulations to show that fragmentation-induced starvation limits the growth of massive stars by forming secondary stars that compete for accreting material, explaining observed stellar system structures.

Contribution

The study introduces the concept of fragmentation-induced starvation as a key process in massive star formation, incorporating radiative heating effects in simulations.

Findings

Fragmentation occurs in dense accretion flows around forming massive stars.

Secondary stars form rapidly and accrete mass, starving the primary star.

Radiative heating leads to fewer, more massive stars and matches observed stellar mass relations.

Abstract

Massive stars influence their surroundings through radiation, winds, and supernova explosions far out of proportion to their small numbers. However, the physical processes that initiate and govern the birth of massive stars remain poorly understood. Two widely discussed models are monolithic collapse of molecular cloud cores and competitive accretion. To learn more about massive star formation, we perform simulations of the collapse of rotating, massive, cloud cores including radiative heating by both non-ionizing and ionizing radiation using the FLASH adaptive mesh refinement code. These simulations show fragmentation from gravitational instability in the enormously dense accretion flows required to build up massive stars. Secondary stars form rapidly in these flows and accrete mass that would have otherwise been consumed by the massive star in the center, in a process that we term fragmentation-induced starvation. This explains why massive stars are usually found as members of high-order stellar systems that themselves belong to large clusters containing stars of all masses. The radiative heating does not prevent fragmentation, but does lead to a higher Jeans mass, resulting in fewer and more massive stars than would form without the heating. This mechanism reproduces the observed relation between the total stellar mass in the cluster and the mass of the largest star. It predicts strong clumping and filamentary structure in the center of collapsing cores, as has recently been observed. We speculate that a similar mechanism will act during primordial star formation.