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| Paper: |
Competitive Accretion in Sheet Geometry and the Stellar IMF |
| Volume: |
440, UP2010: Have Observations Revealed a Variable Upper End of the Initial Mass Function? |
| Page: |
107 |
| Authors: |
Hsu, W.; Hartmann, L.; Heitsch, F.; Gómez, G. C. |
| Abstract: |
We report a set of numerical experiments
addressing the applicability of competitive accretion
to explain the high-mass end of the stellar initial mass function
in a sheet geometry with shallow gravitational potential,
in contrast to most previous simulations which have assumed formation
in a cluster gravitational potential.
Our flat cloud geometry is motivated by models of molecular cloud formation
due to large-scale flows in the interstellar medium.
The experiments consisted of smoothed particle hydrodynamics simulations of gas accretion onto
sink particles formed rapidly from Jeans-unstable
dense clumps placed randomly in
the finite sheet.
We considered both clumps of
equal mass and gaussian distributions of masses,
and either uniform or spatially-varying gas densities.
The sink mass function develops a power law
tail at high masses, with dN/dlogM ∝ M–Γ.
The accretion rates of individual sinks follow M ∝ M2 at high masses; this results in a continual
flattening of the slope of the mass function
towards an asymptotic form Γ∼1
(where the Salpeter slope is Γ = 1.35).
The asymptotic limit is most rapidly reached when starting from
a relatively broad distribution of initial sink masses.
Although these simulations are highly idealized, the results suggest that
competitive accretion may be relevant in a wider variety
of environments than previously considered. |
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