For some sources (e.g. a black body at 100,000 K or the spectrum of a very old star), the temperatures calculated with CMacIonize defer significantly from those of Cloudy: the CMacIonize temperature is high but pretty flat near the centre for a uniform box, while in Cloudy the central temperature is much higher and then falls of. The reason turns out to be double ionized helium: the Cloudy output indicates high ionic fractions for He++ in the central region with the higher temperature. CMacIonize does not have He++ and hence significantly underestimates the photoionization heating.
Adding He++ is very complicated: it requires the addition of an additional helium ion and a thorough change to the ionization balance calculation. Additionally, the addition of a number of other elements with ionization energies close to that of He++ is required to get the cooling right.
The best strategy to embark upon this ambitious change would be to
- first add the atomic data required for He++ and the other metal ions that need to be included. These can be tested independently as part of the existing unit tests.
- then add He++ to the ionization balance by running some fixed temperature simulations. Hopefully it will be possible to benchmark these against Cloudy.
- finally, the additional metals can be added and a full comparison with Cloudy for a high temperature black body can be done. Since the computation of the ionization balance of metals can be implemented independently of the H/He balance, this should not be too hard.
For some sources (e.g. a black body at 100,000 K or the spectrum of a very old star), the temperatures calculated with CMacIonize defer significantly from those of Cloudy: the CMacIonize temperature is high but pretty flat near the centre for a uniform box, while in Cloudy the central temperature is much higher and then falls of. The reason turns out to be double ionized helium: the Cloudy output indicates high ionic fractions for He++ in the central region with the higher temperature. CMacIonize does not have He++ and hence significantly underestimates the photoionization heating.
Adding He++ is very complicated: it requires the addition of an additional helium ion and a thorough change to the ionization balance calculation. Additionally, the addition of a number of other elements with ionization energies close to that of He++ is required to get the cooling right.
The best strategy to embark upon this ambitious change would be to