Chapter 17

Chapter 17 - Note that the following lectures include...

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Note that the following lectures include animations and PowerPoint effects such as fly ins and transitions that require you to be in PowerPoint's Slide Show mode (presentation mode).
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Galaxies With Active Nuclei Chapter 17
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This chapter is important for two reasons. First, it draws together ideas from many previous chapters to show how nature uses the same basic rules on widely different scales. Matter flowing into a protostar, into a white dwarf, into a neutron star, or into the heart of a galaxy must obey the same laws of physics, so we see the same geometry and the same phenomena. The only difference is the level of violence. Second, this chapter is important because the most distant objects we can see in the universe are the most luminous galaxies, and many of those are erupting in outbursts and are thus peculiar. By studying these galaxies, our attention is drawn out in space to the edge of the visible universe and back in time to the earliest stages of galaxy formation. In other words, we are led to think of the origin and evolution of the universe, the subject of the next chapter. Guidepost
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I. Active Galaxies A. Seyfert Galaxies B. Double-Lobed Radio Sources C. Testing The Black Hole Hypothesis D. The Search for a Unified Model E. Black Holes and Galaxy Formation II. Quasars A. The Discovery of Quasars B. Quasar Distances C. Evidence of Quasars in Distant Galaxies D. Superluminal Expansion E. A Model Quasar F. Quasars Through Time Outline
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Active Galaxies Galaxies with extremely violent energy release in their nuclei (pl. of nucleus). “Active Galactic Nuclei” (= AGN) Up to many thousand times more luminous than the entire Milky Way; energy released within a region approx. the size of our solar system!
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The Spectra of Galaxies Taking a spectrum of the light from a normal galaxy: The light from the galaxy should be mostly star light, and should thus contain many absorption lines from the individual stellar spectra.
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Seyfert Galaxies NGC 1566 Circinus Galaxy Unusual spiral galaxies: Very bright cores Emission line spectra. Variability: ~ 50 % in a few months Most likely power source: Accretion onto a supermassive black hole (~10 7 – 10 8 M sun )
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Interacting Galaxies Seyfert galaxy NGC 7674 Active galaxies are often associated with interacting galaxies, possibly result of recent galaxy mergers. Often: gas outflowing at high velocities, in opposite directions Seyfert galaxy NGC 4151
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Cosmic Jets and Radio Lobes Many active galaxies show powerful radio jets Radio image of Cygnus A Material in the jets moves with almost the speed of light (“Relativistic jets”). Hot spots: Energy in the jets is released in interaction with surrounding material
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Radio image superposed on optical image Centaurus A (“Cen A” = NGC 5128): the closest AGN to us. Jet visible in
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This note was uploaded on 11/04/2011 for the course PHYS 227 taught by Professor Professorroberts during the Fall '11 term at BYU.

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Chapter 17 - Note that the following lectures include...

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