Physics 321
Astrophysics II:  Lecture #23
Prof. Dale E. Gary
NJIT

Active Galaxies

Energy Output and Active Galaxies

We have so far discussed the appearance, makeup, and dynamics of normal galaxies, but astronomers have long known of strange objects out there that do not fit into our scheme of normal galaxies.  Some are clearly galaxies, but with some peculiar characteristics.  Other objects are not galaxies themselves, but are thought to be objects at the cores of galaxies.  We will discuss these within a unified framework that focuses on the cores, or nuclei, of galaxies.  The peculiar objects are thus referred to as Active Galactic Nuclei, or AGN.  The single criterion that distinguishes AGN from normal galaxies is energy output:
Types of Active Galactic Nuclei
AGN come in several types:
A Unified Model for AGN
How can all of these very different appearing objects be brought under a single model?  Clearly the underlying theme is the existence of a supermassive black hole, which along with its accretion disk provide the power to run these titanic engines in the centers of galaxies.  The basic picture is exactly the same as we saw with X-ray binaries, but on a much vaster scale.  Important issues:
Using Quasars (QSOs) to Probe the Universe