The four-populations model: a new classification scheme for pre-planetesimal collisions

Abstract

Within the collision growth scenario for planetesimal formation, the growth step from centimetre sized pre-planetesimals to kilometre sized planetesimals is still unclear. The formation of larger objects from the highly porous pre-planetesimals may be halted by a combination of fragmentation in disruptive collisions and mutual rebound with compaction. However, the right amount of fragmentation is necessary to explain the observed dust features in late T Tauri discs. Therefore, detailed data on the outcome of pre-planetesimal collisions is required and has to be presented in a suitable and precise format. We propose and apply a new classification scheme for pre-planetesimal collisions based on the quantitative aspects of four fragment populations: the largest and second largest fragment, a power-law population, and a sub-resolution population. For the simulations of pre-planetesimal collisions, we adopt the SPH numerical scheme with extensions for the simulation of porous solid bodies. By means of laboratory benchmark experiments, this model was previously calibrated and tested for the correct simulation of the compaction, bouncing, and fragmentation behaviour of macroscopic highly porous silica dust aggregates. It is shown that previous attempts to map collision data were much too oriented on qualitatively categorising into sticking, bouncing, and fragmentation events. We show that the four-populations model encompasses all previous categorisations and in addition allows for transitions. This is because it is based on quantitative characteristic attributes of each population such as the mass, kinetic energy, and filling factor. As a demonstration of the applicability and the power of the four-populations model, we utilise it to present the results of a study on the influence of collision velocity in head-on collisions of intermediate porosity aggregates.

14 pages, 11 figures, 5 tables, to be published in Astronomy and Astrophysics

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Cited by in corpus (17)

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• Static compression of porous dust aggregates
• Collisions of CO${}_2$ Ice Grains in Planet Formation
• Free Collisions in a Microgravity Many-Particle Experiment III: The Collision Behavior of sub-Millimeter-Sized Dust Aggregates
• Bouncing Behavior of Microscopic Dust Aggregates
• Preplanetary scavengers: Growing tall in dust collisions
• Growth and fragmentation of centimetre-sized dust aggregates: the dependence on aggregate size and porosity
• Experiments on centimeter-sized dust aggregates and their implications for planetesimal formation
• Macroscopic Dust in Protoplanetary Disks - From Growth to Destruction
• Understanding planet formation using microgravity experiments
• Colliding Decimetre Dust
• Collisions of inhomogeneous pre-planetesimals
• Compression Behaviour of Porous Dust Agglomerates
• Crossing barriers in planetesimal formation: The growth of mm-dust aggregates with large constituent grains
• Formulating Compressive Strength of Dust Aggregates from Low to High Volume Filling Factors with Numerical Simulations
• Selective Aggregation Experiments on Planetesimal Formation and Mercury-Like Planets