Bondi-Hoyle-Littleton accretion and the upper mass stellar IMF

Abstract

We report on a series of numerical simulations of gas clouds with self-gravity forming sink particles, adopting an isothermal equation of state to isolate the effects of gravity from thermal physics on the resulting sink mass distributions. Simulations starting with supersonic velocity fluctuations develop sink mass functions with a high-mass power-law tail $dN/d\log M\propto M^{\Gamma }$, $\Gamma =-1\pm 0.1$, independent of the initial Mach number of the velocity field. Similar results but with weaker statistical significance hold for a simulation starting with initial density fluctuations. This mass function power-law dependence agrees with the asymptotic limit found by Zinnecker assuming Bondi-Hoyle-Littleton (BHL) accretion, even though the mass accretion rates of individual sinks show significant departures from the predicted $\mdot \propto M^2$ behavior. While BHL accretion is not strictly applicable due to the complexity of the environment, we argue that the final mass functions are the result of a {\em relative} $M^2$ dependence resulting from gravitationally-focused accretion. Our simulations may show the power-law mass function particularly clearly compared with others because our adoption of an isothermal equation of state limits the effects of thermal physics in producing a broad initial fragmentation spectrum; $\Gamma \to -1$ is an asymptotic limit found only when sink masses grow well beyond their initial values. While we have purposely eliminated many additional physical processes (radiative transfer, feedback) which can affect the stellar mass function, our results emphasize the importance of gravitational focusing for massive star formation.

Accepted by MNRAS. 10 pages, 14 figures

References in corpus (6)

• Analytical theory for the initial mass function: CO clumps and prestellar cores
• Limiting Accretion onto Massive Stars by Fragmentation-Induced Starvation
• Gravitational fragmentation and the formation of brown dwarfs in stellar clusters
• Infall-Driven Protostellar Accretion and the Solution to the Luminosity Problem
• The Jeans mass and the origin of the knee in the IMF
• Clump Lifetimes and the Initial Mass Function

Cited by in corpus (8)

• An excess of massive stars in the local 30 Doradus starburst
• Are fibres in molecular cloud filaments real objects?
• Structure and Expansion Law of HII Regions in structured Molecular Clouds
• Magnetized converging flows towards the hot core in the intermediate/high-mass star-forming region NGC 6334 V
• Kinematics and Structure of Star-forming Regions: Insights from Cold Collapse Models
• Stellar mass spectrum within massive collapsing clumps III. Effects of temperature and magnetic field
• Disc truncation in embedded star clusters: Dynamical encounters versus face-on accretion
• Gravitational Focusing and the Star Cluster Initial Mass Function