Oral Presentation
Feedback in Massive Star Formation
Presenter: Kei Tanaka (Osaka University / NAOJ)
Massive stars play a lot of essential roles in a wide range of astrophysical settings throughout cosmic history, and thus it is crucial to understand how they form. We are theoretically and observationally investigating the impact of feedback in massive star formation via core accretion. We developed the first theoretical model, including multiple feedback processes, i.e., MHD disk wind, radiation pressure, photo-ionization, and stellar winds (Tanaka et al. 2017). Our model suggested that, similar to low-mass counterpart, the MHD disk wind is the dominant feedback to determine rather than radiative feedback even in the formation of very massive stars (>100Msun) (see also Staff, Tanaka et al. 2019). Along with the theoretical works, we also conducted high-resolution ALMA observations to unveil massive protostars that are still deeply embedded in molecular clouds. Thanks to the power of ALMA, we detected rich structures such as massive proto-binaries, rotating envelope/disk systems, synchrotron jets, a photo-evaporation outflow via multi-band imaging with molecular/recombination lines (Zhang+Tanaka et al. 2019abc; Tanaka et al. in prep.). As a whole, the dynamics of accretion/outflow motions can be (roughly) explained as the scale-up of low-mass star formation. Using radiative transfer modeling, we measured the mass-loss rate by the photo-evaporation from a 40Msun protostar as ~3e-5Msun/yr, which is very consistent with our theoretical predictions. Finally, to connect the present-day and the early universe, we will also discuss massive star formation at low metallicity environments based on our new theoretical and observational studies (Tanaka et al. 2018; Shimonishi+Tanaka et al., in prep.).
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