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18 - Structure of the Universe

18 - Structure of the Universe. Extragalactic Distance Scale. Cepheids M V =-3.35logΠ-2.13+2.13(B-V) Π=period (days) Novae M V (max)=-9.96-2.31log(Δm/day) first 2 mags Planetary Nebulae Luminosity Function M 5007 (brightest)=-4.48

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18 - Structure of the Universe

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  1. 18 - Structure of the Universe

  2. Extragalactic Distance Scale • Cepheids MV=-3.35logΠ-2.13+2.13(B-V) Π=period (days) • Novae MV(max)=-9.96-2.31log(Δm/day)first 2 mags • Planetary Nebulae Luminosity Function M5007(brightest)=-4.48 • Globular Cluster Luminosity Function MB(turnover)=-6.5 • Tully-Fisher MH=-10.01log(2vr/sin i)+3.61 • D-σ logD=1.333logσ + C (for relative distances) • Brightest Red Supergiants MV=-8.0 • SN Ia MB(max)=-19.6 (but correct for decline time and redshift) • Brightest Galaxy in Cluster MV=-22.82 • Surface Brightness Fluctuations

  3. Cepheid Distance Scale • L’s for PL relation from Cluster Fitting and a few (~6?) measured parallaxes • 1997 (Feast & Catchpole) - Hipparcos parallaxes for 223 Cepheids, of which 26 carry a lot of weight (accurate π’s and spread in P) • PLC relation due to width of instability strip (Sandage) • Dependent on metallicity • Affected by extinction (in near-IR brightnesses are less, too). • Blending light with nearby stars • Different methods give different results

  4. Globular Cluster Luminosity Function

  5. Planetary Nebula Luminosity Function

  6. Tully-Fisher Relation (in near-IR)

  7. D-σ Relation(recently brightness- D-σ =“fundamental plane”)

  8. Brightest Galaxy in Cluster

  9. Supernovae Ia’s

  10. 35 SN Ia’s 1-day averages Correcting for stretch and time dilation Original Data Corrected for Time Dilation (redshift z) Corrected for Stretch

  11. Slipher (1914-1925) - Radial Velocities of GalaxiesMost (“nearby”) galaxies exhibit spectral shift to longer wavelengths - “redshifts”

  12. UniversalExpansion

  13. 1929 - Hubble enters the picture Note: data originally published in 1929 PNAS, not 1936!

  14. The Hubble Law actually first introduced by Lamaitre in 1927 These are valid only for small z. For larger z, need to use true relativitstic formulation: This gives the Hubble Law (for space with flat geometry - which it seems to be) as:

  15. NOTE Implications: • This sort of law would be derived by any observer in the universe - everyone sees the same law. Everything is (overall) moving away from everything else at the same rate per unit distance. • Universe is expanding - space is expanding, carrying the matter with it. • The universe need not have a “center” for this to be true. • The age of a universe with no acceleration/deceleration is simply 1/H0. • If universal, such a law allows one to determine the distance of an object from its value of z.

  16. Hubble & Humason 1931 extend Hubble Law to larger distances

  17. H0 from SN Ia’s WMAP gives H0=71

  18. Large-Scale Structure(on many scales) • Groups (N<50, D~2 Mpc) • Clusters (N~50 (“poor”) - thousands (“rich”), D~8 Mpc) “regular” - spherical & centrally condensed (Coma) “irregular” - not (Virgo) • Superclusters - clusters of clusters

  19. The Local Group

  20. M 82 M 81 Group NGC 3077 M 81

  21. M 81 Group in H I

  22. M82 RGB Chandra (X-rays) VLA & Merlin (radio)

  23. Leo I Group (M 96 Group)

  24. Nearby Groups

  25. Virgo Cluster

  26. Coma Cluster

  27. Dark Matter 1933 - Fritz Zwicky uses the virial theorem to deduce the existence of “dunkle Materie” (dark matter) in the Coma cluster. Helvetica Physica Acta, 6, 110 (1933)

  28. M/L for Coma ~500, compared to ~3 locally. Considers the possibility there may be “internebular matter” that is giving mass estimates of clusters of galaxies too high a value. Considers independent methods to get masses of individual galaxies... “Method iv involves the observation of gravitational lens effects. Measurements of deflecting angles combined with data on the absolute distance of the “lens nebula” from the observer suffice to determine the mass of the lens nebula. The chances for the successful application of this method grow rapidly with the size of the available telescopes.” - Zwicky, ApJ, 86, 217 (1937).

  29. Hot Intergalactic Gas X-ray emission from Perseus Cluster. Probably >50% of all baryonic matter. Accounts for a fraction of the “dark matter”. The rest is “non-baryonic”.

  30. Abell 1795 “cooling flow”

  31. Red: radio synchrotron Blue: X-rays

  32. Local Supercluster

  33. Even LARGER Scale Structure CfA - single slice

  34. CfA “hockey puck” “Great Wall” Local Supercluster Pisces-Perseus supercluster

  35. Density fluctuations & Non-Hubble Flow

  36. Origin of Structure - Cold Dark Matter

  37. Lensing & Dark Matter

  38. Red: X-ray emitting gas Blue: Lensing material

  39. HUDF - Beckwith et al. (Nov. 2006 AJ 132, 1729-1755)

  40. Galaxy Evolution Filters

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