" The paper that originally identified objects named for Seyfert referred to six of these; in fact, orbital resonance may result in the high prevalence of active nuclei in the barred variety of these.
These bodies were modeled as the results of small disturbances to a thin, cold disk in the density-wave theory named for Lin and Shu, while these objects have a resonance named for Bertil Lindblad, who identified an objection to existing models of them called the "winding problem." The paper that originally identified objects named for Seyfert referred to six of these; in fact, orbital resonance may result in the high prevalence of active nuclei in the barred variety of these. For 10 points, identify these objects, whose subclass a contains predominantly Population II stars in their bulges, at the center of which may exist a supermassive black hole, and in which a large number of Population I stars, young and blue, may be found in their arms, examples of which include the Andromeda Galaxy and the Milky Way.
These bodies were modeled as the results of small disturbances to a thin, cold disk in the density-wave theory named for Lin and Shu, while these objects have a resonance named for Bertil Lindblad, who identified an objection to existing models of them called the "winding problem.
{spiral galaxies} [prompt on {galaxies}] [AW]