OUTFLOW FEEDBACK REGULATED MASSIVE STAR FORMATION IN PARSEC-SCALE CLUSTER-FORMING CLUMPS

Abstract

(Abridged) We investigate massive star formation in turbulent, magnetized,\nparsec-scale clumps of molecular clouds including protostellar outflow feedback\nusing Enzo-based MHD simulations with accreting sink particles and effective\nresolution $2048^3$. We find that, in the absence of regulation by magnetic\nfields and outflow feedback, massive stars form readily in a turbulent,\nmoderately condensed clump of $\\sim 1,600$ solar masses, along with a cluster\nof hundreds of lower mass stars. The massive stars are fed at high rates by (1)\ntransient dense filaments produced by large-scale turbulent compression at\nearly times, and (2) by the clump-wide global collapse resulting from\nturbulence decay at late times. In both cases, the bulk of the massive star's\nmass is supplied from outside a 0.1 pc-sized "core" that surrounds the star. In\nour simulation, the massive star is clump-fed rather than core-fed. The need\nfor large-scale feeding makes the massive star formation prone to regulation by\noutflow feedback, which directly opposes the feeding processes. The outflows\nreduce the mass accretion rates onto the massive stars by breaking up the dense\nfilaments that feed the massive star formation at early times, and by\ncollectively slowing down the global collapse that fuel the massive star\nformation at late times. The latter is aided by a moderate magnetic field of\nstrength in the observed range. We conclude that the massive star formation in\nour simulated turbulent, magnetized, parsec-scale clump is outflow-regulated\nand clump-fed (ORCF for short). An important implication is that the formation\nof low-mass stars in a dense clump can affect the formation of massive stars in\nthe same clump, through their outflow feedback on the clump dynamics.\n