Automated Tidal Debris Analysis to Unlock the History of Galactic Mergers

Galaxies are believed to grow through hierarchical mergers, in which high-mass galaxies cannibalize the satellite dwarf galaxies that orbit them. Dwarf galaxies that are tidally disrupted by their much more massive hosts form tidal debris substructures, which encode information about their progenitors and can open a window into the merger histories of galaxies. Upcoming surveys, like LSST & WFIRST, are expected to capture vast numbers of images of tidal debris substructures in galactic halos. We developed an automated method for measuring the properties of tidal debris, which will allow us to efficiently analyze these future datasets. The algorithm is capable of distinguishing shell-like and stream-like tidal debris, which are the most distinct morphologies, and measuring their luminosities and scales. These properties hint at the shape of the satellite orbit, as well as the duration of the epoch of accretion and the relative masses of the satellite and host galaxy. We demonstrate our algorithm on images from n-body simulations and explore how identifying the properties of these substructures will help us unravel the accretion histories of galaxies in our Universe and allow us to probe theories of hierarchical galaxy formation.