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Spiral GalaxiesElliptical GalaxiesIrregular GalaxiesClassification of GalaxiesProperties of GalaxiesStephan’s Quintet – Colliding galaxiesThe “Anntenae” Galaxies – a case studyGalactic Train WrecksCollisional AftermathRing Galaxies – the “splash”Galactic SuperwindsThe Magellanic CloudsThe Galactic NeighborhoodThe “Local Group” of GalaxiesMembers of the Local GroupAnd outward…Galaxy ClustersGalactic Cannibals – Central CD EllipticalsMaking a CD galaxyinto the Universe…Large Scale StructureDark Matter - rotation curvesDark Matter – cluster speedsWhat could the dark matter be?Dark Matter :gravitational lensingWIMPS and Cold Dark MatterSpiral 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 studyGalactic Train WrecksCollisional AftermathRing 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 onlyThe Galactic NeighborhoodThe “Local Group” of GalaxiesMembers of the Local GroupAnd 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 galaxyinto 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 empty.Dark Matter - rotation curvesRotation curves imply the mass-to-light ratios of galaxies go up as we look on larger scales: Sun M/L=1, solar neighborhood  M/L=3, galaxy  M/L=50Dark Matter – cluster speedsgalaxy clusters  M/L=200-500From average speed of galaxies – the cluster would fly apart From X-ray gas held in – several million degrees and extensiveWhat could the dark matter be?1) Normal but dark matter (“baryonic”) : rocks, white or brown dwarfs?2) Black holes or neutron stars? Too much metals would have been produced.Anyway, there is a fundamental reason from the Big Bang this can’t be it…Dark Matter :gravitational lensingThe mass required to produce the observed lensing is much higher than the luminous mass. This is a direct observation of gravity due to dark matter.WIMPS and Cold Dark MatterCould dark matter be some kind of new particles which interact very weakly with matter (like neutrinos do) but massive, and not moving relativistically? Experiments at Berkeley and elsewhere are looking for them (guaranteed Nobel


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Berkeley ASTRON 10 - Galaxies

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