1The Syllabus:Quasars & Active galactic Nuclei (AGN)[28.2] Unified model of AGN …(Skip [28.1], [28.3]) [18.2] Accretion Disk description pp. 661-666[24.4] The Galactic CenterDec 7,9,11[26.2] The formation of galaxiesNov 30, Dec 2,4Thanksgiving HolidayFri Nov 27[26.1] Interaction of galaxiesNov 23,25What is dark matter?[30.2] The origin of structure; WMAP measurements.Nov 16,18,20The Structure of the Universe & Evolution of Galaxies[27.3] Clusters of galaxies[28.4] Using quasars to probe the universe (gravitational lenses) Nov 9,11,13• Present-day structure.• Evidence for Dark Matter.• Gravitational lenses.• What is Dark Matter?•Hot vs. cold DM• The growth of structure.• Initial fluctuations.• WMAP.• Bottom-up structureformation.( turkey break)• The Quasar Era.• Evolution to modern-day galaxies.• Chemical enrichmentrevisited.• The first stars.The agenda:The Structure of the Universe• The Local Group• 2 main mass concentrations• MW + satellites–LMC–SMC• M31 + satellites–M32–M332The Brightest Members of the Local Group (an old list)Galaxy Clusters1000’s of galaxiesHercules Cluster3The Local Supercluster• Biggest component: Virgo Cluster (1014M).• Local Supercluster (1015M)Virgo Cluster(2000 galaxies)Blue = 0oKRed = 4oKBlue = 2.724oKRed = 2.732oKDipole Anistropy4Structure upon structure• Local Group• Virgo Cluster (1014M).• All part of Local Supercluster (1015M)• Local Supercluster is part of streaming motion towards “Great Attractor”•1016-17M• located 45 Mpc away.• Detected by extra motions superimposed on “Hubble Flow”.Virgo Cluster(2000 galaxies)LocalSuperclusterBubbles and VoidsIncluding SDSS (Sloan Digital Sky Survey)cz(km s-1) Î211 MpcHarvard Center for Astrophysics (CfA) survey (1985)5Bubbles and VoidsIncluding SDSS (Sloan Digital Sky Survey)Projected on skyThe Evidence for Dark MatterMass/Luminosity Ratio• Local stellar luminosity function: M/L = 0.67• Our Galaxy, at larger scales:• Local motions ⊥ disk (Oort limit): M/L ~ 3-5• Flat rotation curve > 30• Escape speed > 30• Pop II dynamics (glob. clusters, etc.) ~ 276Dark matter in nearby galaxies• Flat rotation curves in other spiral galaxies • ==> dark halos• typically M/L > 28h > 20• Central regions of Elliptical Galaxies• Virial theorem:• or… compare surface brightness, velocity dispersions to isothermal sphere model• M/L ~ 12h ~ 9RGMr52=σ3DProjectedDensity distribution for an isothermal sphereE galaxy X-ray halos • Hot x-ray emitting gas in E galaxies is in hydrostatic equilibrium•ρ(r), T(r) measured from X-ray bremsstrahlung emission:[CO 27.18, pg. 1066]Volume emissivity:amplitudefreq.distr.pressuredensity[CO fig. 27.17][CO 27.17]Energy ÆFlux Æρ2)(rrGMdrdP−=pBmTkPµρ=∂∂−∂∂−=rTrmGTrkrMpBlnlnlnln)(ρµHydrostaticequilibrium:Ideal gas law:M(r)M87 is best caseGiant E1 at center of Virgo clusterÎ M/L ~ 750P+dPPDensity = ρ7• Local Group Dynamics –The Impending MW – M31 Collision• Approaching each other at 119 km/s• Current separation: r = 770 kpc Î collision in r/v ~ 6x109yrs.• Rough mass estimate from Kepler’s laws•P = PERIOD = age of Universe with r = 0 at t = 0 • Binney & Tremaine: • more exact analysis, same answer (M = 3-5x1012M☼)• M/L ~ 100Galaxy Groups & Clusters[CO 27.16]a = semi-major axis(kinetic energy) = -(potential energy) + (total energy)Dark Matterso farMass/Luminosity• Local stellar luminosity function: M/L = 0.67• Our Galaxy, at larger scales:• Local motions ⊥ disk (Oort limit): M/L ~ 3-5• MW Rotation curve > 30• Escape speed > 30• Pop II dynamics (glob. clusters, etc.) ~ 27 • Flat rotation curves in other spirals > 20• E galaxy virial theorem 9• X-ray halo of M87 > 750 • Local Group dynamics
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