Galaxies

• Types:
  
  • Spiral: ongoing star formation
  • Barred spiral, star formation in barred sprial
  • Elliptical
  • Irregular: Sextans A, LMC, SMC
  • colliding/merging galaxies
    
• Internal motions: rotation curves
  
  • the pioneers: Fritz Zwicky, Vera Rubin
    
  • geometry of the problem
  • M33: optical, with 21-cm rotation curve
  • NGC 2997: optical global and zoom; hot off the slit spectrograph
  • typical rotation curves examples, by galaxy type
• clusters

Changing Gears: The Big Picture

Cosmology

Where are the Galaxies: Structure of the Universe

• cosmological principle: homogeneous & isotropic
• actual data: 2dF Galaxy Redshift Survey
  • survey geometry
  • results in 3-D

Galaxy Motion Relative to Us

• Hubble's law
• Hubble motion: artist's conception

The Expansion of the Universe

• demanded by homogeneity and isotropy
• scale factor
• raisin cake analogy
  balloon analogy

The Center of the Universe?

• demands of homogeneity and isotropy
• alternative location: a short drive southwest of campus
  Philo, IL: downtown landmark, zoom