The Multi-Physics Feedback of Massive Stars

Rolf Kuiper, IAAT, Emmy Noether Group leader - 22.01.18

Abstract:

In the course of their accretion phase, massive (proto)stars impact their natal environment in a variety of feedback effects such as thermal heating, MHD-driven protostellar outflows, radiative forces, and photoionization. Here, I present our most recent simulation results in terms of the relative strength of the feedback components and the size of the reservoir from which the forming stars gain their masses.

We find that photoionization and HII regions dominate the feedback ladder only at later times, after the star has already contracted down to the zero-age main sequence, and only on large scales. Specifically, photoionization yields a broadening of the bipolar outflow cavities and a reduction of the gravitational infall momentum by about 50%, but does not limit the stellar mass accretion. On the other hand, we find radiation forces restrain the gravitational infall toward the circumstellar disk, impact the gravito-centrifugal equilibrium at the outer edge of the disk, and eventually shut down stellar accretion completely. The most massive star formed in the simulations accreted 95 Msol before disk destruction; this mass was drawn-in from an accretion reservoir of ~ 240 Msol and ~ 0.24 pc in radius.

Concluding, our most up-to-date simulations include all of the feedback effects mentioned above and allow us to shed light on the physical reason for the upper mass limit of present-day stars.