"Equation of State" of Dust Aggregates

Abstract

We study dust aggregate collisions to construct a model of their structure evolution in protoplanetary disks. We carry out three-dimensional simulations of aggregate collisions and examine the compression and disruption processes. We take clusters of ballistic cluster-cluster aggregation (BCCA) as initial structures and study their head-on collisions. For aggregate compression due to collision, we succeed in obtaining a scaling law on the gyration radius of the resultant aggregate as a function of the impact energy using the fractal dimension of compressed aggregates. Furthermore, we derive an ``equation of state'' of aggregates which reproduces the scaling law for compression. This equation of state would be useful to describe the density evolution of dust aggregates during their growth.