2019MNRAS.487.2969C

Small dwarf companions have been long thought to have minimal influence on their host galaxy's evolution without undergoing direct impacts to the host's disc. However, in light of recent discoveries of coplanar, corotating satellite structures around the Milky Way, Andromeda, and Centaurus A, we use an N-body/test particle simulation to show that low-mass dwarf satellites within such structures are able to exert significant influence on their host's disc, driving spiral waves and inducing stellar scattering. This is accomplished through quasi-periodic alignments of multiple small satellites within the structure that emulate the gravitational influence of a single, larger satellite such as Sagittarius Dwarf or the Large Magellanic Cloud. We find that the coplanar, corotational nature of such structures allows for repeated alignments on short enough time-scales to overcome damping within the disc, and in a consistent enough fashion to continually drive spiral waves over the course of 2 Gyr of simulation time. The spirals driven by this phenomenon tend to be flocculent and many armed due to the irregular intervals over which alignments occur. We additionally find that while the aligned satellites are able to induce noticeable thickening of the disc, their ability to drive surface density profile evolution is secondary to other effects.