Tapir Seminar
Friday, October 16, 2:00pm, 370 Cahill

Elena D'Onghia, CfA, Harvard

"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 we propose 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, 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 that we called "Tidal Near-Resonance Theory" I will show the
efficiency and nature of this process and its applicability to a huge number of problems: from the
formation of star tails in galaxies, to the formation of dwarf spheroidal galaxies, to planetary systems.