The Shape of the Vertical Action Distribution Locates the Scatterers that Heat the Galactic Disc

The Milky Way's stellar disc is thicker than the cold gas layer from which its stars form.

The Milky Way's stellar disc is thicker than the cold gas layer from which its stars form. What scatters stars onto orbits with greater vertical motion remains unresolved. Scatterers could fill the disc volume, as bending waves or dark substructure would, or could be confined to…