The Impact of Feedback During Massive Star Formation by Core Accretion

Abstract

We study feedback during massive star formation using semi-analytic methods, considering the effects of disk winds, radiation pressure, photoevaporation and stellar winds, while following protostellar evolution in collapsing massive gas cores. We find that disk winds are the dominant feedback mechanism setting star formation efficiencies (SFEs) from initial cores of ~0.3-0.5. However, radiation pressure is also significant to widen the outflow cavity causing reductions of SFE compared to the disk-wind only case, especially for >100Msun star formation at clump mass surface densities Sigma<0.3g/cm2. Photoevaporation is of relatively minor importance due to dust attenuation of ionizing photons. Stellar winds have even smaller effects during the accretion stage. For core masses Mc~10-1000Msun and Sigma~0.1-3g/cm2, we find the overall SFE to be 0.31(Rc/0.1pc)^{-0.39}, potentially a useful sub-grid star-formation model in simulations that can resolve pre-stellar core radii, Rc=0.057(Mc/60Msun)^{1/2}(Sigma/g/cm2)^{-1/2}pc. The decline of SFE with Mc is gradual with no evidence for a maximum stellar-mass set by feedback processes up to stellar masses of ~300Msun. We thus conclude that the observed truncation of the high-mass end of the IMF is shaped mostly by the pre-stellar core mass function or internal stellar processes. To form massive stars with the observed maximum masses of ~150-300Msun, initial core masses need to be >500-1000Msun. We also apply our feedback model to zero-metallicity primordial star formation, showing that, in the absence of dust, photoevaporation staunches accretion at ~50Msun. Our model implies radiative feedback is most significant at metallicities ~10^{-2}Zsun, since both radiation pressure and photoevaporation are effective in this regime.

18 pages, 7 figures, accepted to ApJ

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Cited by in corpus (5)

• Radiation Transfer of Models of Massive Star Formation. IV. The Model Grid and Spectral Energy Distribution Fitting
• Massive Outflows Driven by Magnetic Effects II: Comparison with Observations
• Upper stellar mass limit by radiative feedback at low-metallicities: metallicity and accretion rate dependence
• Discovery of a Photoionized Bipolar Outflow towards the Massive Protostar G45.47+0.05
• Outflow-Confined HII regions. II. The Early Break-Out Phase