HLRB Project h1343
Ionization Feedback in Massive Star Formation
ITA Heidelberg
Proposing Institution
ITA Heidelberg
Project Manager
Dr. Thomas Peters
Albert-Ueberle-Str. 2
69120 Heidelberg
Abstract
Massive stars have a strong impact on the universe. With masses of up to 100 solar massesand lifetimes of only a few million years, they produce all the heavy elements during theirlifetimes and in the final stage of their lifes, the supernova explosions. These explosionsinject the generated material back into the ambient interstellar medium (ISM), where the nextgeneration of stars is already waiting to be born. One of these supernova explosions alsosupplied the material from which our own solar system, the earth and all living creatures formed.Despite the utter importance of massive stars, very little is known about their origin. Not only is the formation of massive stars hard to observe, also its theoretical understandingis awfully incomplete. Massive protostars already begin hydrogen burning whilethey are still accreting. It turns out that this radiation feedback is a crucial point in understandingmassive star formation. Calculations of spherically symmetric accretion show that the dust hasto overcome a high radiation pressure. This radiation pressure mayhalt the accretion and limit the mass of the star. But not only the radiation pressure,also the ionization of the neutral gas may stop accretion. Ionization heats the gas to 10^4 K,with corresponding sound speeds of 10 km/s. This gas may escape fromthe gravitational attraction of the star and thus turn off the supply of mass from the envelope.We want to address the question of feedback in massive star formation by means of three-dimensionaladaptive mesh simulations with the FLASH code. We plan to apply a newly developedradiation module for simulations of massive star formation that includes a detailedtreatment of the ionization physics. The ultimate goal is to study the ionization feedback of amassive protostar on its protostellar disk and to investigate whether ionization is a limiting mechanismthat determines how much mass massive stars can attain.
