The Lyman Limit

• physics, data
• awesome example: QSO absober Lyman limit systems

"Metal" Lines

• physics: resonance lines
• astrophysics: atmospheric opacity
• awesome examples:
  • in the solar spectrum
  • in quasar spectra

Hydrogen Spectroscopy Redux: the Balmer Jump

• Balmer series
• stellar spectra: here and here; note the Balmer jump

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
  • galaxy rotation curves at 21 cm
  • cosmic 21 cm radiation evidence for monopole and fluctuations; LOFAR, SKA