2018MNRAS.481.2590L

We extend the work of Chang & Chakrabarti to find simple scaling relations between the density response of the gas disc of a spiral galaxy and the pericentre distance and mass ratio of a perturbing satellite. From the analysis of results from a test particle code, we obtained a simple scaling relation for the density response due to a single satellite interacting with a galactic disc, over a wide range of satellite masses and pericentre distances. We have also explored the effects of multiple satellites on the galactic disc, focusing on cases that are commonly found in cosmological simulations. Here, we use orbits for the satellites that are drawn from cosmological simulations. For these cases, we compare our approximate scaling relations to the density response generated by satellites, and find that for two satellite interactions, our scaling relations approximately recover the response of the galactic disc. We have also examined the observed H I data in the outskirts of several spiral galaxies from The H I Nearby Galaxy Survey (THINGS) sample and compared the observed perturbations to that of cosmological simulations and our own scaling relations. While small perturbations can be excited by satellites drawn from cosmological simulations, we find that large perturbations (such as those that are seen in some THINGS galaxies like M51) are not recovered by satellites drawn from cosmological simulations that are similar to Milky Way galaxies.