Institute for Advanced Study Informal Astrophysics Seminar

This talk explains the formation of galaxies of different morphological types (aka the Hubble Sequence): spirals vs ellipticals, disks vs spheroids. The talk includes theory, observation, and simulation, and is aimed at a general astrophysics audience. Some highlights of the talk are the following: (1) The morphologies of galaxies are closely related to their specific angular momenta. (2) Disk-dominated galaxies have about the same specific angular momenta as their dark-matter halos; spheroid-dominated galaxies have about five times less. (3) Feedback by young stars (stellar radiation and winds, supernovae, etc) and active galactic nuclei is crucial for understanding the angular momenta of galaxies and hence their morphologies and hence the Hubble sequence. (4) The relations between the specific angular momenta and sizes of galaxies and their halos are nearly constant over the redshift range 0 < z < 3; galaxies and halos grow together nearly homologously.