Circumventing the radiation pressure barrier in the formation of massive stars via disk accretion

TL;DR

This study uses advanced radiation hydrodynamics simulations to demonstrate that disk accretion can overcome radiation pressure barriers, enabling the formation of extremely massive stars beyond previous limits.

Contribution

First 2D simulations of the entire accretion phase for massive star formation, highlighting the role of dust sublimation fronts and anisotropic radiation in surpassing spherical accretion mass limits.

Findings

High-mass stars formed far beyond spherical accretion limits.

Stable bipolar outflows driven by radiation pressure observed.

Accretion disks effectively shield and sustain mass growth.

Abstract

We present radiation hydrodynamics simulations of the collapse of massive pre-stellar cores. We treat frequency dependent radiative feedback from stellar evolution and accretion luminosity at a numerical resolution down to 1.27 AU. In the 2D approximation of axially symmetric simulations, it is possible for the first time to simulate the whole accretion phase (up to the end of the accretion disk epoch) for the forming massive star and to perform a broad scan of the parameter space. Our simulation series show evidently the necessity to incorporate the dust sublimation front to preserve the high shielding property of massive accretion disks. While confirming the upper mass limit of spherically symmetric accretion, our disk accretion models show a persistent high anisotropy of the corresponding thermal radiation field. This yields to the growth of the highest-mass stars ever formed in multi-dimensional radiation hydrodynamics simulations, far beyond the upper mass limit of spherical accretion. Non-axially symmetric effects are not necessary to sustain accretion. The radiation pressure launches a stable bipolar outflow, which grows in angle with time as presumed from observations. For an initial mass of the pre-stellar host core of 60, 120, 240, and 480 Msun the masses of the final stars formed in our simulations add up to 28.2, 56.5, 92.6, and at least 137.2 Msun respectively.