The Role of Gravity in Producing Powerlaw Mass Functions
Abstract
Numerical simulations of star formation have found that a powerlaw mass function can develop at high masses. In a previous paper, we employed isothermal simulations that created large numbers of sinks over a large range in masses to show that the powerlaw exponent of the mass function, {dN}/d{log}M\propto {M}^{{{Γ }}}, asymptotically and accurately approaches Γ = 1. Simple analytic models show that such a power law can develop if the mass accretion rate \dot{M}\propto {M}^{2}, as in BondiHoyle accretion; however, the sink mass accretion rates in the simulations show significant departures from this relation. In this paper, we show that the expected accretion rate dependence is more closely realized provided the gravitating mass is taken to be the sum of the sink mass and the mass in the near environment. This reconciles the observed mass functions with the accretion rate dependencies, and demonstrates that powerlaw upper mass functions are essentially the result of gravitational focusing, a mechanism present in, for example, the competitive accretion model.
 Publication:

The Astrophysical Journal
 Pub Date:
 November 2018
 DOI:
 10.3847/15384357/aae6c8
 arXiv:
 arXiv:1810.03682
 Bibcode:
 2018ApJ...868...50K
 Keywords:

 ISM: kinematics and dynamics;
 stars: formation;
 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 11 pages, 10 figures, accepted by ApJ