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Multiple Feedback in Low-Metallicity Massive Star Formation

Published online by Cambridge University Press:  30 October 2019

Kei E. I. Tanaka
Affiliation:
Department of Earth and Space Science, Osaka University, Toyonaka, Osaka 560-0043, Japan email: ktanaka@astro-osaka.jp Chile Observatory, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
Jonathan C. Tan
Affiliation:
Department of Space, Earth and Environment, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA
Yichen Zhang
Affiliation:
Star and Planet Formation Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 351-0198, Japan
Takashi Hosokawa
Affiliation:
Department of Physics, Kyoto University, Sakyo, Kyoto 6060-8502, Japan
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Abstract

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We theoretically investigate the impact of feedback and its metallicity dependence in massive star formation from prestellar cores at all metallicity range. We include the feedback by MHD disk winds, radiation pressure, and photoevaporation solving the evolution of protostars and accretion flows self-consistently. Interestingly, we find that the feedback does not set the upper mass limit of stellar birth mass at any metallicity. At the solar metallicity, the MHD disk wind is the dominant feedback to set the star formation efficiencies (SFEs) from the prestellar cores similar to low-mass star formation. The SFE is found to be lower at lower surface density environment. The photoevaporation becomes significant at the low metallicity of Z < 10−2 Z. Considering this efficient photoevaporation, we conclude that the IMF slope is steeper, i.e., massive stars are rarer at the extremely metal-poor environment of 10−5 − 10−3Z. Our study raises a question on the common assumption of the universal IMF with a truncated at 100M. Since the total feedback strength in the cluster/galaxy scale is sensitive to the number fraction of massive stars, the re-evaluations of IMF at various environments are necessary.

Type
Contributed Papers
Copyright
© International Astronomical Union 2019 

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