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Astronomy 305/Frontiers in Astronomy

Astronomy 305/Frontiers in Astronomy. Class web site: http://glast.sonoma.edu/~lynnc/courses/a305 Office: Darwin 329A (707) 664-2655 Best way to reach me: lynnc@charmian.sonoma.edu. Group 11. Great job, group 11!. What does the Universe look like?. What happens when galaxies collide?

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Astronomy 305/Frontiers in Astronomy

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  1. Astronomy 305/Frontiers in Astronomy Class web site: http://glast.sonoma.edu/~lynnc/courses/a305 Office: Darwin 329A (707) 664-2655 Best way to reach me: lynnc@charmian.sonoma.edu Prof. Lynn Cominsky

  2. Group 11 Great job, group 11! Prof. Lynn Cominsky

  3. What does the Universe look like? • What happens when galaxies collide? • How do galaxies cluster? • What are the largest structures in the Universe? • What other types of background radiation exist? • Summary of scales in the Universe Prof. Lynn Cominsky

  4. Cartwheel Galaxy • Wheel shape was formed from collision of two galaxies • Bright stars are forming at the edges of the wheel (105 light years in diameter) • Intruder galaxy is no longer visible This is from HST Prof. Lynn Cominsky

  5. Collisions and Mergers movie • Galaxy collisions contribute to large scale structure formation • Note: galaxies do not make noise when they collide! Prof. Lynn Cominsky

  6. More Galaxy Collision movies Prof. Lynn Cominsky

  7. Galaxy Harassment • Spirals merge to form ellipticals • Biggest elliptical cannibalizes the others to form one giant elliptical in the center of the cluster • Dwarf ellipticals are formed by harassment (high velocity encounters) of low-mass spirals • Detectable arcs of debris are left over – providing fuel for quasars Prof. Lynn Cominsky

  8. Galaxy Harassment movie • Gas is red • Stars are yellow and in a disk initially • Dark matter is blue and in a halo initially • Green are other galaxies in the cluster • Initial spiral becomes warped, and eventually elliptical Prof. Lynn Cominsky

  9. M87 Virgo cluster of galaxies • The Virgo cluster of galaxies is about 65 million light years away • It contains about 2500 galaxies • It is dominated by M87 Prof. Lynn Cominsky

  10. Virgo Cluster • It is the nearest rich cluster of galaxies • Classification - irregular • Covers about 100o of sky or at its distance it spreads out over tens of millions of light years • Recessional velocity is about 0.3% of velocity of light • X-ray emission concentrated around individual galaxies, particularly M84 and M86 • The strong radio galaxy M87 in the Virgo cluster is also a strong source of X-rays Prof. Lynn Cominsky

  11. Virgo/ROSAT M = V2R G X-ray emission from Clusters • Gas in clusters of galaxies is held by mass where: • Mass of hot gas is more than 3 times the mass of the visible light galaxies in the Virgo cluster • Strongest X-rays are around M87 Prof. Lynn Cominsky

  12. Distances to Galaxy Clusters • Brightest Cluster Galaxies: The brightest galaxy in a cluster of galaxies has been used as a standard candle. • But: rich clusters with many galaxies will probably have the most luminous galaxies even though these galaxies are very rare, while the brightest galaxy in less rich clusters are probably not as bright Prof. Lynn Cominsky

  13. Standard Candles • Fobs = Ltrue/(4pd2) where • Fobs = flux observed at Earth • Ltrue = true brightness at source • d = distance from Earth to source • Objects with known luminosities that can be used to calculate distance movie Prof. Lynn Cominsky

  14. Types of Galaxy Clusters • Regular clusters • concentrated central core • well-defined spherical structure • often dominated by a giant galaxy • usually quite rich, M~1015 Mo • most galaxies are elliptical or lenticular • Irregular clusters • no well-defined center • ~half the galaxies are spirals • Often contain subclusters • Probably not steady state Prof. Lynn Cominsky

  15. Optical/La Palma Hydra Cluster • Distance of 840 million light years • Several hundred galaxies in the cluster • 35 million degree gas in center rising to 40 million in the outside • Several million light years across the gas cloud Prof. Lynn Cominsky

  16. Radio/NRAO X-ray/Chandra Hydra Cluster Prof. Lynn Cominsky

  17. Cluster Formation • Formation and evolution of a galaxy cluster (from T6 group at Los Alamos) • Evolution of a Cd galaxy cluster (from John Dubinski at CITA) movies Prof. Lynn Cominsky

  18. How clusters affect galaxy evolution movie • Ram pressure and turbulent stripping of gas from a spiral galaxy as it falls through the hot ICM of a rich galaxy cluster (by Vicent Quilis with Ben Moore) • The galaxy model is 3d with a stellar disk, bulge + dark matter halo. The colours show the gas density in a thin slice centered on the disk Prof. Lynn Cominsky

  19. Small Cluster • X-rays from this smaller cluster were discovered by ROSAT • Hot gas engulfs the two bright elliptical galaxies • It is about 500 million light years away Prof. Lynn Cominsky

  20. Very Distant Cluster • This is a very red cluster, located at Z~1 • It is the most distant cluster discovered by HST • It may be too far away to have formed in a dense universe Prof. Lynn Cominsky

  21. Very Distant Cluster • This cluster is 8 billion light years away, so it formed when the universe was half its present age • It is also very red • It should not exist if the Universe is dense Prof. Lynn Cominsky

  22. Merging Clusters • A2256 cluster has about 500 galaxies • It is about 10 million light years across • It is about 1 billion light years away • The 80 million degree gas is brightest in the center where two clusters are merging Prof. Lynn Cominsky

  23. Merging Clusters • A2142 cluster • The 50 million degree gas is coolest in the center where two clusters have finished merging • The gas outside the center is 100 million degrees – heated by the collision • Chandra image Prof. Lynn Cominsky

  24. ESO/Optical Cannibal Cluster • A3827 is about 1.5 billion light years away • The central dominant galaxy is eating five smaller galaxies Prof. Lynn Cominsky

  25. 3 Mpc Coma Cluster • Coma cluster has about 1000 galaxies • It is located near the north galactic pole • It is about 250 million light years away (80 Mpc) • Large bright central cluster is merging with smaller galaxy group at the lower right Prof. Lynn Cominsky

  26. Perseus Cluster • One of the closest galaxy clusters at a distance of 300 million light years • Part of the Perseus Pisces supercluster which is 15 degrees across and has over 1000 galaxies Prof. Lynn Cominsky

  27. Local Supercluster • The Local supercluster contains the Virgo cluster of galaxies as well as about 50 galaxy groups Prof. Lynn Cominsky

  28. Local Supercluster Superclusters • Superclusters usually have 3-10 clusters of galaxies • They are not gravitationally bound • Our local supercluster contains the Virgo cluster (at 16 Mpc) and extends about 40- 50 Mpc Prof. Lynn Cominsky

  29. The body of the stickman is due to the Coma cluster His arms form “walls” “Stickman” • “Slice” –style Redshift survey pioneered by Margaret Geller, Marc Davis and John Huchra • Distance is plotted vertically as given by redshifts Prof. Lynn Cominsky

  30. Las Campanas Survey • Done by Shectman et al. • Largest redshift survey • Clearly shows walls and voids • 75-80% of space is devoid of bright galaxies • Typical distance between 2 galaxies is around 7.5 Mpc • Typical distance between 2 clusters is around 20 Mpc Prof. Lynn Cominsky

  31. Flyby universe movie • Las Campanas data – notice the walls and voids as you fly by Prof. Lynn Cominsky

  32. Walls and Voids • Universe looks like soap bubbles in 3D • Galaxies occur on the bubble surfaces • Superclusters are formed where bubbles merge • Walls are made of elongated superclusters – the largest is the “Great Wall” - about 100 Mpc in length at a distance of 100 Mpc • Voids are about 100 Mpc in diameter – are 90% of space • Clusters of galaxies are bright spots on the walls Prof. Lynn Cominsky

  33. Large Scale Structure formation • Comparison of the 2df galaxy redshift survey to mock catalogue constructed from a Lambda CDM simulation (from Ben Moore) movie Prof. Lynn Cominsky

  34. XMM-Newton LSS Survey • X-ray emitting clusters of galaxies • About 15 per square degree Prof. Lynn Cominsky

  35. Lyman-alpha forest studies • Lyman alpha is the name of the electron transition from n=1 to n=2 in Hydrogen • When the H atom is hit by a photon, the electron can get enough energy to make this transition, and the photon is removed from the initial beam from the source Prof. Lynn Cominsky

  36. quasar clouds Lyman-alpha forest studies • The observer sees light from the distant quasar that is absorbed due to intervening H-clouds • However, because the Universe is expanding, the Ly-a absorption lines occur at different wavelengths, which tell you the distance to each cloud Prof. Lynn Cominsky

  37. Quasar clustering studies • Measurements of positions of QSOs can be used to trace large scale structure • This shows the spectra of 10 QSOs as a function of redshift Prof. Lynn Cominsky

  38. Quasar clustering studies • 2dF survey measured redshifts from 250,000 galaxies and 23,000 QSOs • Used camera with two-degree wide field on AAT to measure up to 400 redshifts simultaneously Prof. Lynn Cominsky

  39. 2dF results • Walls and voids also seen in southern hemisphere Prof. Lynn Cominsky

  40. Formation of Large Scale Structure • Simulation by Martin White shows the evolution of structure starting with fluctuations in the Cosmic Microwave Background movie Prof. Lynn Cominsky

  41. The End of Greatness movie • Most recent surveys are so large that the largest structures (about 100 Mpc) are smaller than the survey size • This is a 200 Mpc simulation from Ben Moore (using LCDM) Prof. Lynn Cominsky

  42. Where are we going? • The Milky Way Galaxy is falling towards the Virgo cluster at ~300 km/s • The Virgo cluster is falling towards the Hydra-Centaurus superclusteralso at ~300 km/s But the Hydra-Centaurus cluster is also falling towards something….. Prof. Lynn Cominsky

  43. Abell 3627 near the Great Attractor Great Attractor • ~1016 solar masses concentrated 65 Mpc away in the direction of Centaurus • The “Great Attractor” seems to be pulling in the Hydra-Centaurus super-cluster • But only 10% that amount of visible matter can be seen! Prof. Lynn Cominsky

  44. Wedge Plot Activity • These data are from CLEA’s LSS lab • Each group should plot 20 of the galaxies on the wedge plot transparency • Then we will put all the plots together • How many clusters do you see? • Why is the wedge plot a better representation of the measurements than the linear plot? Prof. Lynn Cominsky

  45. Scales in the Universe • Solar system • http://www.csupomona.edu/~ajm/materials/scales.html • 12 billion km in diameter • Milky Way Galaxy  40,000 pc (~120,000 light years) • Local Group  few Mpc • Larger Cluster  several Mpc • Great Wall  100 Mpc • Observable Universe  3,000-6,000 Mpc (10-20 billion light years) Prof. Lynn Cominsky

  46. Infrared Background • The Cosmic InfraRed Background (CIRB) is the radiation from stars in many faint galaxies. • It is what is left over after emission from our Solar System and our Galaxy has been subtracted away • Near IR is redshifted starlight from distant galaxies • Far IR is starlight absorbed by dust and reemitted Prof. Lynn Cominsky

  47. Infrared Background Reemitted by dust Red shifted starlight CMB Prof. Lynn Cominsky

  48. Zodiacal Light • Diffuse visible light reflected from interplanetary dust • Orbits in same plane as planets • Brightest (in North) in fall and spring Prof. Lynn Cominsky

  49. Ultraviolet Background • The last spectral region to be explored in detail • Narrow bands have been searched • Many mechanisms exist across the UV band • Fluorescent emission from molecular H2 • Emission lines from highly ionized atoms • Hot intergalactic medium? • Shock heating from cosmic structure formation? Prof. Lynn Cominsky

  50. X-ray Background • ROSAT 0.75 keV map Shows smooth blue background plus bright superbubble ring at D=150 pc with R= ~100 pc Prof. Lynn Cominsky

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