Elena D’Onghia


Resonant Stripping as the Origin of Dwarf Spheroidal Galaxies


The most dark matter dominated galaxies known are the dwarf spheroidals, but their origin is still uncertain. The recent discovery of ultra-faint dwarf spheroidals around the Milky Way further challenges our understanding of how low-luminosity galaxies originate and evolve because of their even more extreme paucity of gas and stars relative to their dark matter content. By employing numerical simulations, I will show that interactions between dwarf disc galaxies can excite a gravitational resonance that immediately drives their evolution into spheroidals. This effect, which is purely gravitational in nature, applies to gas and stars and is distinct from other mechanisms which have been proposed up to now to explain the origin of dwarf spheroidals, such as merging, galaxy-galaxy harassment and more general heating processes, or tidal and ram pressure stripping. Using a new analytic formalism I developed based on the linear perturbation theory I will show the nature and the efficiency of the resonant process and its applicability from planetary systems to the formation of tails of stars and streams of gas, like the Magellanic stream.