AFFIRM MASS - Accretion Flows and Feedback In Realistic Models of MASsive Star formation

• Applicant: Professor Dr. Rolf Kuiper
• Subject Area: Astrophysics and Astronomy
• Term: from 2014 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 259131583

Context: Massive star formation – especially at the upper mass limit – is expected to be influenced or even controlled by stellar feedback in form of radiation forces and photoionization. But numerical simulations have covered the > 100 M⊙ regime only in very rare cases and the metallicity dependence of massive star feedback has been explored mainly for the primordial and present-day star formation case without a thorough scan of the parameter space in between these two extreme cases.Methods: In order to perform simulations of stellar feedback in the regime of the most massive stars, we will utilize our recently developed numerical framework. This star formation code denotes a unique tool in the sense that it is capable of taking into account protostellar outflows, radiation forces, and photoionization feedback simultaneously (along with stellar evolution and dust evolution).Aims: We propose to study the impact of these feedback effects and their interplay onto the forming accretion disk – outflow system in multi-physics numerical models of the collapse of massive pre-stellar cores from the sub-AU regime up to the most distinctive features of high-mass star formation, namely protostellar outflows and HII regions. We will determine the star formation efficiency of the pre-stellar core collapse in the regime of the upper mass limit of stars including its dependence on metallicity.Based on analytical arguments, we expect a transition from dominating photoionization feedback in the regime of low metallicities (early universe) to dominating radiation forces for higher metallicities (present-day case). We will test these analytically motivated hypotheses by quantitatively determining the feedback efficiencies in the regime of the upper mass limit of stars.Résumé: We will use the proposed 6th year extension of the research group to investigate radiation forces and photoionization feedback in the regime of the upper mass limit of stars and determine their metallicity dependence. Special focus is given on the transition from the regime of dominating radiation forces in the present-day case to the regime of dominating photoionization feedback in the primordial star formation case.Additionally to these straight-forward tasks, follow-up tasks of the currently ongoing projects include comparison of our recent numerical models to observations of disk fragmentation and stellar multiplicity, the merging of the already deployed magneto-hydrodynamics capabilities of the code into our stellar feedback framework, and the merging of the already deployed module for thermal dissociation and ionization of hydrogen into our stellar feedback framework.

• DFG Programme: Independent Junior Research Groups