This week! Icko Iben Lecturer Prof. Wendy Freedman, U. Chicago

• expert in distance measures, resolved stellar populations, and the Hubble Constant
• most-cited paper: Freedman+ 2001, followup to Hubble 1929
  iconic plots: original and update

How I spent last week

The 21 cm Line

• physics: hyperfine splitting
• awesome examples:
  • the sky in 21 cm; disk map: velocity-colored and in velocity space
  • galaxy M33 in optical and in 21 cm; multiwavelength, composite
  • galaxy rotation curves at 21 cm
  • cosmic 21 cm radiation evidence for monopole and fluctuations; LOFAR, SKA

Atomic Collisions

• cross sections
• critical densities

Nebular Diagnostics