Lecture 12 - Heating and Cooling of HII regions

Question 1

Name the four relevant heating and cooling processes of HII regions

Answer 1

1. Heating by photoionization
2. Cooling by recombination radiation
3. Cooling by free-free emission
4. Cooling by collisionally excited line radiation

Question 2

Are recombination electrons more or less energetic than average electrons?

Answer 2

Less, since slow electrons are more likely to recombine