CO Traces Molecular Hydrogen (but not always)

• from the spectra we measure:
• excitation temperature and opacity
• and column density
• assume H2 to CO abundance ratio
  • 4.5E+21 molecules/sq-cm average
  • 14.0E+21 molecules/sq-cm peak (10^4/cc)
  • Tex = 10 K
  • Tex > 25 K on the rim