Radiation pressure feedback in the formation of massive stars

TL;DR

This study uses advanced radiation hydrodynamics simulations to show that massive star formation is facilitated by disk-induced anisotropic radiation escape and gravitational torques, overcoming radiation pressure barriers.

Contribution

It introduces frequency-dependent radiation feedback and resolves the dust sublimation front, providing new insights into the mechanisms enabling massive star growth.

Findings

High anisotropy in radiation field preserves accretion.

Radiation escapes through optically thin atmosphere, reducing feedback.

Stars can reach over 137 solar masses in simulations.

Abstract

We investigate the radiation pressure feedback in the formation of massive stars in 1, 2, and 3D radiation hydrodynamics simulations of the collapse of massive pre-stellar cores. In contrast to previous research, we consider frequency dependent stellar radiation feedback, resolve the dust sublimation front in the vicinity of the forming star down to 1.27 AU, compute the evolution for several 10^5 yrs covering the whole accretion phase of the forming star, and perform a comprehensive survey of the parameter space. The most fundamental result is that the formation of a massive accretion disk in slowly rotating cores preserves a high anisotropy in the radiation field. The thermal radiation escapes through the optically thin atmosphere, effectively diminishing the radiation pressure feedback onto the accretion flow. Gravitational torques in the self-gravitating disk drive a sufficiently high accretion rate to overcome the residual radiation pressure. Simultaneously, the radiation pressure launches an outflow in the bipolar direction, which grows in angle with time and releases a substantial fraction of the initial core mass from the star-disk system. Summarized, for an initial core mass of 60, 120, 240, and 480 Msol these mechanisms allow the star to grow up to 28.2, 56.5, 92.6, and at least 137.2 Msol respectively.