Galaxies

Galactic vs Extragalactic Astronomy

Some History

• Charles Messier and his objects
• Curtis-Shapley debate (1920)
• Hubble (the man) discovers a cephied in M31
• Hubble (the telescope): Cephieds in M100
  the recordholder: NGC 4603

Galaxy Types

• Elliptical
  • cD: NGC 4881 in the Coma cluster
  • giant ellipticals: M87 optical, IR
    NGC 3377 optical, IR
  • dwarf ellipticals: NGC 147
• Lenticular
  • M85
  • NGC 5866/M102?
  • NGC 2787
• Spiral
  • M104
  • NGC 891
• Irregular
  • NGC 2207 and IC 2163
  • Arp 220
• Starburst
  • M82
  • NGC253
  • M94 optical, IR
  • NGC 1313
  • NGC 4314
  • NGC 1808
• Hubble's tuning fork

Photometry: Imaging Galaxies

• Surface brightness
• Sky brightness, e.g., at Mauna Kea
  sources include: zodiacal light from interplanetary dust, sky glow, more sky glow, anthropogenic sources
• Projection effects