Outflow Feedback Regulated Massive Star Formation in Parsec-Scale Cluster Forming Clumps

We investigate massive star formation in turbulent, magnetized, parsec-scale clumps of molecular clouds including protostellar outflow feedback using three dimensional numerical simulations of effective resolution 2048. The calculations are carried out using a block structured adaptive mesh refinement code that solves the ideal MHD equations including self-gravity and implements accreting sink particles. We find that, in the absence of regulation by magnetic fields and outflow feedback, massive stars form readily in a turbulent, moderately condensed clump of ∼ 1, 600 M⊙(containing ∼ 10 2 initial Jeans masses), along with a cluster of hundreds of lower mass stars. The massive stars are fed at high rates by (1) transient dense filaments produced by large-scale turbulent compression at early times, and (2) by the clump-wide global collapse resulting from turbulence decay at late times. In both cases, the bulk of the massive star’s mass is supplied from outside a 0.1 pc-sized “core” that surrounds the star. In our simulation, the massive star is clump-fed rather than core-fed. The need for large-scale feeding makes the massive star formation prone to regulation by outflow feedback, which directly opposes the feeding processes. The outflows reduce the mass accretion rates onto the massive stars by breaking up the dense filaments that feed the massive star formation at early times, and by collectively slowing down the global collapse that fuel the massive star formation at late times. The latter is aided by a moderate magnetic field of strength in the observed range (corresponding to a dimensionless clump mass-to-flux ratio λ ∼ a few); the field allows the outflow momenta to be deposited more efficiently inside the clump. We conclude that the massive star formation in our simulated turbulent, magnetized, parsecscale clump is outflow-regulated and clump-fed (ORCF for short). An important KIPAC, SLAC, and Physics Department, Stanford University, Menlo Park, CA 94025 Astronomy Department, P.O. Box 400325, University of Virginia, Charlottesville, VA 22904; [email protected] Faculty of Education, Niigata University, 8050 Ikarashi-2, Niigata 950-2181, Japan; also visiting astronomer at Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan SLAC-PUB-13871