The Role of Outflows, Radiation Pressure, and Magnetic Fields in Massive Star Formation

Abstract

Stellar feedback in the form of radiation pressure and magnetically driven collimated outflows may limit the maximum mass that a star can achieve and affect the star formation efficiency of massive prestellar cores. Here we present a series of 3D adaptive mesh refinement radiation-magnetohydrodynamic simulations of the collapse of initially turbulent, massive prestellar cores. Our simulations include radiative feedback from both the direct stellar and dust-reprocessed radiation fields, and collimated outflow feedback from the accreting stars. We find that protostellar outflows punch holes in the dusty circumstellar gas along the star's polar directions, thereby increasing the size of optically thin regions through which radiation can escape. Precession of the outflows as the star's spin axis changes due to the turbulent accretion flow further broadens the outflow, and causes more material to be entrained. Additionally, the presence of magnetic fields in the entrained material leads to broader entrained outflows that escape the core. We compare the injected and entrained outflow properties and find that the entrained outflow mass is a factor of ∼3 larger than the injected mass and the momentum and energy contained in the entrained material are ∼25% and ∼5% of the injected momentum and energy, respectively. As a result, we find that, when one includes both outflows and radiation pressure, the former are a much more effective and important feedback mechanism, even for massive stars with significant radiative outputs. Unified AstronomyThesaurus concepts: Interstellar magnetic fields (846); Star formation (1569); Radiative magnetohydrodynamics (2009); Massive stars (732); Stellar jets (1607); Stellar feedback (1602)

STARFORGE: Towards a comprehensive numerical model of star cluster formation and feedback

“…A comprehensive treatment of feedback is needed because different feedback channels are effective on different scales, and can interact non-linearly. For example, direct radiation pressure from a massive star is ineffective if it couples deep within the star's potential well (Krumholz 2018), and radiation pressure in general may be subdominant to protostellar outflows for regulating the growth of individual massive stars (Rosen & Krumholz 2020). But by regulating accretion or punching optically thin holes, outflows could help photons to couple their momentum farther away from the star, eventually allowing them to disrupt the host GMC (Fall, Krumholz & Matzner 2010;Murray, Quataert & Thompson 2010;Hopkins, Quataert & Murray 2012;Raskutti, Ostriker & Skinner 2016;Kim, Kim & Ostriker 2018;Grudić et al 2018a;Hopkins et al 2020a).…”

“…The values of f w and f K do matter: in Paper 2, we find that the product f w f K affects the IMF peak. The specific value of θ 0 is likely to be unimportant because in any realistic turbulent accretion scenario J s will generally tend to precess during accretion over an angular region much larger than θ 0 (Rosen & Krumholz 2020), and even without precession jet cavities will expand in the perpendicular direction, opening up an ever-increasing solid angle (Arce & Sargent 2006;Offner et al 2011). In our tests, we will show that our results are insensitive to variations in θ 0 of at least a factor of 10, which is consistent with prior hydrodynamic outflow simulations carried out by Offner & Arce (2014).…”

Continuity of accretion from clumps to Class 0 high-mass protostars in SDC335

“…In particular, modelling the effects of the collapsing clumps, precession, turbulence, and magnetic fields (see e.g. Rosen & Krumholz 2020) show that the outflow morphologies are narrower along the outflow axis than the bicone morphology would suggest. Given these effects and the fact that we cannot reproduce the observed LWR for outflows A and B using the biconical morphology, we instead propose an alternate morphology to limit the inclination angle ranges of these outflows.…”

“…Shu et al 2000;Pudritz et al 2007). Figure 17 (adapted from Rosen & Krumholz 2020) shows two snapshots from a 3D RHD simulation that models the collapse of a turbulent massive (150 M ) pre-stellar core into a massive stellar system and includes radiative feedback and collimated outflows that are launched along the stars' angular momentum vectors (see subgrid model description by Cunningham et al 2011). These snapshots show the column density of the molecular material that is entrained by the protostellar outflows from the stars that have formed.…”

STARFORGE: the effects of protostellar outflows on the IMF

“…The mass-loss of accreting protostars is dominated by high velocity bipolar outflows that can significantly affect their environment (see reviews of Frank et al 2014;Bally 2016). These outflows are thought to be driven by highly collimated bipolar jets that entrain the ambient gas (Rosen & Krumholz 2020). These jets in turn are launched by MHD interactions between the protostar and the accretion disc (Shu et al 1988;Pelletier & Pudritz 1992), with radiation pressure also contributing to their driving (Kuiper et al 2010;Vaidya et al 2011).…”