On the Formation of Massive Stars

By H. Yorke, C. Sonnhalter. 2002

361 citations recorded by the source corpus.

We calculate numerically the collapse of slowly rotating, nonmagnetic, massive molecular clumps of masses 30, 60, and 120 M☉, which conceivably could lead to the formation of massive stars. Because radiative acceleration on dust grains plays a critical role in the clump's dynamical evolution, we have improved the module for continuum radiation transfer in an existing two-dimensional (axial symmetry assumed) radiation hydrodynamic code. In particular, rather than using "gray" dust opacities and "gray" radiation transfer, we calculate the dust's wavelength-dependent absorption and emission simultaneously with the radiation density at each wavelength and the equilibrium temperatures of three grain components: amorphous carbon particles, silicates, and "dirty ice"-coated silicates. Because our simulations cannot spatially resolve the innermost regions of the molecular clump, however, we cannot distinguish between the formation of a dense central cluster or a single massive object. Furthermore, we cannot exclude significant mass loss from the central object(s) that may interact with the inflow into the central grid cell. Thus, with our basic assumption that all material in the innermost grid cell accretes onto a single object, we are able to provide only an upper limit to the mass of stars that could possibly be formed. We introduce a semianalytical scheme for augmenting existing evolutionary tracks of pre-main-sequence protostars by including the effects of accretion. By considering an open outermost boundary, an arbitrary amount of material could, in principal, be accreted onto this central star. However, for the three cases considered (30, 60, and 120 M☉ originally within the computation grid), radiation acceleration limited the final masses to 31.6, 33.6, and 42.9 M☉, respectively, for wavelength-dependent radiation transfer and to 19.1, 20.1, and 22.9 M☉ for the corresponding simulations with gray radiation transfer. Our calculations demonstrate that massive stars can in principle be formed via accretion through a disk. The accretion rate onto the central source increases rapidly after one initial free-fall time and decreases monotonically afterward. By enhancing the nonisotropic character of the radiation field, the accretion disk reduces the effects of radiative acceleration in the radial direction—a process we call the "flashlight effect." The flashlight effect is further amplified in our case by including the effects of frequency-dependent radiation transfer. We conclude with the warning that a careful treatment of radiation transfer is a mandatory requirement for realistic simulations of the formation of massive stars.

Subfields: Astronomy and Astrophysics, Fluid Flow and Transfer Processes

View Paper: https://www.semanticscholar.org/paper/e6a3410561d730a130cadb0f04767c2d1fdbf5a4

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Citations in the corpus

The earliest phases of high-mass star formation: a 3 square degree millimeter continuum mapping of Cygnus X (2007, background): “High-mass stars are known to form in dense cores within molecular cloud complexes, by accretion (Yorke & Sonnhalter 2002; Krumholz et al. 2007) and/or coalescence (e.g. Bonnell et al. 2001).”
The Formation of Stellar Clusters in Turbulent Molecular Clouds: Effects of the Equation of State (2002, background): “Yorke & Sonnhalter (2002) demonstrated that high-mass stars can form in collapsing gas clumps via disk accretion very much the same way as low mass stars are believed to do.”
H II REGIONS: WITNESSES TO MASSIVE STAR FORMATION (2010, methodology): “For example, we use a ray-tracing algorithm to describe ionizing and non-ionizing radiation while Yorke & Sonnhalter (2002); Krumholz et al. (2007b, 2009b); Price & Bate (2009) rely on flux-limited diffusion to follow the radiation field.”
A spectroscopic survey on the multiplicity of high-mass stars (2012, background): “Both observations of massive circumstellar disks (Shepherd, Claussen & Kurtz 2001; Chini et al. 2004; Cesaroni et al. 2005; Patel et al. 2005; Kraus et al. 2010) and theoretical calculations (Yorke & Sonnhalter 2002; Krumholz et al. 2009; Kuiper et al. 2010) seem to favour the accretion scenario.”
The Birth of High-Mass Stars: Accretion and/or Mergers? (2005, background): “Yorke & Sonnhalter (2002) modeled the formation of massive stars with the inclusion of these effects, demonstrating that direct accretion can produce stars up to 20 to 30 M⊙ by accretion from a disk.”
ONE HUNDRED FIRST STARS: PROTOSTELLAR EVOLUTION AND THE FINAL MASSES (2013, methodology): “The nested-grid method (e.g., Yorke & Kaisig 1995; Yorke & Bodenheimer 1999; Yorke & Sonnhalter 2002) is employed in order to achieve an extremely wide dynamic range.”
EVOLUTION OF MASSIVE PROTOSTARS VIA DISK ACCRETION (2010, background): “So far, various formation scenarios, such as monolithic collapse of massive dense cores (e.g., Yorke & Sonnhalter 2002; McKee & Tan 2002, 2003; Krumholz et al. 2007, 2009), and the competitive accretion with global infall of the cluster-forming clumps (e.g., Bonnell et al. 1998; Bonnell, Vine &…”
Massive star formation: nurture, not nature (2004, background): “The simulation formed six stars with masses greater than 10 M⊙ with a maximum stellar mass of ≈ 27 M⊙, ignoring any radiative feedback (e.g. Yorke & Kruegel 1977; Yorke & Sonnhalter 2002).”
LIMITING ACCRETION ONTO MASSIVE STARS BY FRAGMENTATION-INDUCED STARVATION (2010, background): “Hydrodynamic simulations in two (Yorke & Sonnhalter 2002) and three (Krumholz et al. 2009, Kuiper et al. 2010, in prep.) dimensions using a flux-limited diffusion approach to the transport of non-ionizing radiation strongly support this picture.”
EVOLUTION OF MASSIVE PROTOSTARS WITH HIGH ACCRETION RATES (2008, background): “It has been shown that the deceleration effect of infrared light is diminished by reduced dust opacity (WC87), non-spherical accretion (e.g., Nakano 1989; Yorke & Sonnhalter 2002), and other various processes (e.g., see McKee & Ostriker 2007 for a recent review).”
CIRCUMVENTING THE RADIATION PRESSURE BARRIER IN THE FORMATION OF MASSIVE STARS VIA DISK ACCRETION (2010, methodology): “Contrary to the stable radiation pressure-driven outflows in Yorke & Sonnhalter (2002), they discovered in their own three-dimensional (3D; frequencyaveraged) radiation hydrodynamic simulations (Krumholz et al. 2007, 2009) an instability in the outflow region, leading to further accretion onto the…”
Theory of Star Formation (2007, background): “Yorke & Sonnhalter (2002) have carried out the most detailed axisymmetric numerical simulations to date.”
The Formation of the First Stars. II. Radiative Feedback Processes and Implications for the Initial Mass Function (2007, background): “…hand, the dust couples the pressure of the UV continuum radiation to the gas very effectively, and it remains to be determined whether this limits the final mass of the star; e.g., Yorke & Sonnhalter (2002) find that it does, whereas Krumholz et al. (2005a) have not found evidence that it does.”
The physics of star formation (2003, background): “…be able to build up a larger mass before radiation pressure terminates the accretion (Nakano 1989; Jijina and Adams 1996); a detailed calculation by Yorke and Sonnhalter (2002) of collapse with rotation that incorporates radiation pressure and the formation of a viscous disk shows that in this…”
Photoionizing feedback in star cluster formation (2005, background): “In particular, there has been considerable debate as to whether or not stars more massive than ∼10 M can form by conventional accretion, due to the effect of radiation pressure on dust (Wolfire & Cassinelli 1986, 1987; Yorke & Sonnhalter 2002; Edgar & Clarke 2003, 2004).”
Toward Understanding Massive Star Formation (2007, methodology): “Yorke & Sonnhalter (2002) showed by calculating frequency-dependent radiation transfer that the flashlight effect is further enhanced by the fact that the central star’s optical and UV radiation blows out material in the polar direction, reducing back-scattering of radiation toward the disk.”