  Understanding the collisional outcomes of dust aggregates and dependence on
material properties of the constituting particles is of great importance toward
understanding planet formation. Recent numerical simulations have revealed that
interparticle tangential friction plays a crucial role in energy dissipation
during collisions between porous dust aggregates; however, the importance of
friction on the collisional growth of dust aggregates remains poorly
understood. Here we demonstrate the effects of interparticle tangential
friction on the collisional growth of dust aggregates. We performed numerical
simulations of collisions between equal-mass porous dust aggregates consisting
of cohesive and frictionless spheres. We changed the collision velocity and
impact angle systematically and calculated the collisional growth efficiency as
a function of the collision velocity. We found that the threshold velocity for
collisional growth decreases when dust aggregates are made of frictionless
spheres as compared to frictional spheres. Our results highlight the importance
of tangential interactions on the collisional behavior of dust aggregates and
indicate that the predictive equation for threshold velocity should be
reconstructed.
