Spiral GalaxiesElliptical GalaxiesIrregular GalaxiesClassification of GalaxiesProperties of GalaxiesStephan’s Quintet – Colliding galaxiesThe “Anntenae” Galaxies – a case studyRing Galaxies – the “splash”Galactic SuperwindsThe Magellanic CloudsOur Immediate Galactic NeighborhoodMembers of the Local GroupM31 vs Milky WayCollisional AftermathAnd outward…Galaxy ClustersGalactic Cannibals – Central CD EllipticalsMaking a CD galaxyThe Core of M87 (at the center of Virgo)Giant Radio LobesSeyfert GalaxiesQuasars (Quasi-stellar Objects)Host Galaxies of QuasarsSupermassive Black HolesMeasuring the Monster’s MassImages of Active Galaxy disksUnification of Active Galactic Nucleiinto the Universe…Large Scale StructureSpiral GalaxiesElliptical GalaxiesIrregular GalaxiesClassification of GalaxiesProperties of GalaxiesSpirals Ellipticals IrregularsMass [typical; range](solar masses)1011 ; 109 - 10121011.5 ; 106 - 10131010 ; 108 - 1011Size (pc) 104- 105.5104- 106103- 105Color Blue arms,reddish bulgereddish bluishLuminosity 108 - 1010105 - 1011107- 109Stellar Populations Pops I & II Pop II Pop I (Pop II)Interstellar medium Yes Very little Still someRotation Yes (disk) no Not a lotFraction 30% 20% 50% Other galaxy types : Peculiar, Interacting, Ring, Starburst, Dwarf,Luminous Infrared, Active Nuclei, Damped Lyman-alphaStephan’s Quintet – Colliding galaxiesThe “Anntenae” Galaxies – a case studyRing Galaxies – the “splash”Head-on collisions can produce a “ripple” of star formation that expands outwards.Galactic SuperwindsThe Magellanic CloudsLarge Magellanic Cloud Small Magellanic CloudSouthern Hemisphere onlyThese are the nearest irregular galaxies. There are others even closer, being torn apart by our Galaxy (last discovery: 2003 in Canis Major).Our Immediate Galactic NeighborhoodMembers of the Local GroupM31 vs Milky WayBefore the Sun dies, we may collide and merge with the Andromeda Galaxy… (not quite sure yet about this)Collisional AftermathAnd outward…Galaxy ClustersVirgoComaNotice the giant ellipticals at the centers of many clusters.These are an example of “galactic cannibalism”.Galactic Cannibals – Central CD EllipticalsAt the heart of rich clusters, galaxies pass through the center and are disrupted and collected.Making a CD galaxyThe Core of M87 (at the center of Virgo)Giant Radio LobesMany such jets are seen. If they last long enough, they can blast out of the galaxy for millions of light years: the largest single coherent objects in the universe.Seyfert GalaxiesIncreasing exposure times….Some galaxies have unusually bright nuclei…Quasars(Quasi-stellar Objects)QSOStarStrange “stars” were found with spectral lines that turned out to be normal lines but at extremely high red Doppler shifts. The expansion of the Universe means that they must be VERY far away, yet they were not too faint. Even Seyfert nuclei would not be bright enough. The energy output would have to be up to 100’s of times that from a whole normal galaxy, but the source was point-like.Host Galaxies of QuasarsFinally, we were able to obtain deep images of quasars, and show that indeed they are extremely bright galactic nuclei. The only power source that is adequate is a supermassive black hole, eating up to several solar masses per year.Supermassive Black HolesYou know the Milky Way has a 3 million solar mass BH at its center. Are they common? Bigger?Centaurus ALuminosities seem to require them.How could we prove the theory?A billion solar-mass black hole is still only the size of the solar system.Measuring the Monster’s MassImages of Active Galaxy disksRecently, the theory of AGN has received spectacular visual confirmation from the Hubble Space Telescope.Unification of Active Galactic NucleiDepending on what the viewing angle is, what we see can be rather different. This is now sorted out.into the Universe…Large Scale StructureOn the largest scales (100 million ly) the Universe takes on a “foamy” appearance, with great filaments and walls of galaxies and clusters, surrounding great “voids” that are relatively
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