EPoS Contribution
EPoS Contribution
Feedback in Massive Star Formation - On the effects of radiation pressure, stellar winds, and ionization on disk accretion, outflow launching, mass loss, and the upper mass limit of stars

Rolf Kuiper
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California,USA
Massive stars easily achieve luminosities that their radiation pressure, stellar winds, and ionization play a major role in shaping the circumstellar environment. On top of the impact of the radiation pressure, we are now studying the effects of these subsequent feedback mechanisms. Their influence on the accretion disk, the outflow, and large-scale rotating tori is determined in 1D, 2D, and 3D radiation hydrodynamics simulations of collapsing pre-stellar cores of gas and dust. Therein, the evolution of the stellar environment is resolved down to the order of 1 AU (logarithmically decreasing towards larger distance to the star) and the stellar irradiation feedback is computed by use of a highly accurate frequency-dependent ray-tracing (RT) approach. Recently we depicted the importance of this RT step in revealing the sustained stability of radiation-pressure-dominated outflow cavities during the formation of massive stars. In contrast, making use of the gray flux-limited diffusion approximation (FLD) highly underestimates the absorption probability in the cavity shell. As a result, FLD artificially leads to a configuration prone to the so-called radiative Rayleigh-Taylor instability. The evolution of the pre-stellar environment is computed for several 100 kyr (up to a maximum of 14 free-fall times), including the whole accretion phase of the forming star. In this manner, we are able to conclude on the importance of the various feedback effects also regarding their role in determining the upper mass limit of stars in general. In our 2D simulation survey, we check the outcome of these numerical experiments for a variety of numerical parameter and initial conditions, step-by-step uncovering the broad parameter space. Preliminary, we could deduct that in a decent range of the initial angular momentum the most massive stars will form rather from 'lower mass' - but condensed - cores than in flatter ones, although they might contain much more mass. Proceeding on the assumption that this preliminary result holds for a larger range of initial conditions, this would disfavor the effect of competitive accretion to play a major role in the formation of the most massive stars. Furthermore, we will report on the effects of synchronously ongoing stellar evolution (with the aid of the STELLAR code by Harold Yorke) as well as our current investigation of the shielding properties of the inner dust-free gas disk.
H. Yorke, JPL, USA
T. Hosokawa, JPL, USA
N. Turner, JPL, USA
T. Henning, MPIA, Germany
H. Klahr, MPIA, Germany
H. Beuther, MPIA, Germany
Key publication