For 10 points, name these large astronomical collections of billions of stars, examples of which include the Milky Way.
The differential rotation of these objects can be described by the Oort's A and B constants. Equations named after Faber-Jackson and Tully-Fisher relate the (*) stellar velocity dispersion of these objects to their luminosity. Vera Rubin's study of the rotation curves of these objects provided a strong piece of evidence for the existence of dark matter, and the tuning fork organizes these objects on a diagram. Lenticular examples of these objects are intermediate in classification between the elliptical and spiral types. For 10 points, name these large astronomical collections of billions of stars, examples of which include the Milky Way.
The differential rotation of these objects can be described by the Oort's A and B constants.
galaxy (or galaxies)