Table 2.
Wavelengths and ionisation potential of the relevant ion for each emission line.
| Line name | Wavelength | String ID | Ionisation potential | Fixed ratio |
|---|---|---|---|---|
| (air) [Å| | [eV] | |||
| Hydrogen Balmer lines | ||||
| Hβ | 4861.35 | HB4861 | 13.60 | no |
| Hα | 6562.79 | HA6562 | 13.60 | no |
| Low-ionisation lines | ||||
| [N I]λ5197 | 5197.90 | NI5197 | — | No |
| [N I]λ5200 | 5200.26 | NI5200 | — | No |
| [N II]λ5754 | 5754.59 | NII5754 | 14.53 | No |
| [O I]λ6300 | 6300.30 | OI6300 | — | No |
| [O I]λ6364 | 6363.78 | OI6363 | — | 0.33 [O I]λ6300 |
| [N II]λ6548 | 6548.05 | NII6548 | 14.53 | 0.34 [N II]λ6584 |
| [N II]λ6584 | 6583.45 | NII6583 | 14.53 | No |
| [S II]λ6717 | 6716.44 | SII6716 | 10.36 | No |
| [S II]λ6731 | 6730.82 | SII6730 | 10.36 | No |
| High-ionisation lines | ||||
| [O III]λ4959 | 4958.91 | OIII4958 | 35.12 | 0.35 [O III]λ5007 |
| [O III]λ5007 | 5006.84 | OIII5006 | 35.12 | No |
| [He I]λ5876 | 5875.61 | HeI5875 | 24.58 | No |
| [S III]λ6312 | 6312.06 | SIII6312 | 23.34 | No |
Notes. All lines are corrected for the Milky Way foreground contribution. Wavelengths are taken from the National Institute of Standards and Technology (NIST; https://physics.nist.gov/PhysRefData/ASD/lines_form.html), and are Ritz wavelengths in air except for the H Balmer lines, in which case we use the ‘observed’ wavelength in air as reported in NIST. The DAP string name is used to identify the correct extension in the MAPS files. Ionisation potentials are taken from Draine (2011). Lines redder than ∼7000 Å are currently not fitted.
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