Table 1.
UV emission line notations and ionization energies.
| Atomic | Wavelength | Short notation |
Transition | EIonization |
Expected | |||
|---|---|---|---|---|---|---|---|---|
| ion | [Å] | Main | Blue comp. | Red comp. | [eV] | [Ry] | flux ratio | |
| H I | 1216 | Lyα | H0 recombination | 13.60 ( ⋆ ) | 1.00 ( ⋆ ) | |||
| N V( † ) | 1239, 1243 | N V | N V1 | N V2 | N3+→ N4+ | 77.47 | 5.69 | f(N V1)/f(N V2) = 2(a),(b),(c) |
| C IV( † ) | 1548,1551 | C IV | C IV1 | C IV2 | C2+→ C3+ | 47.89 | 3.52 | f(C IV1)/f(C IV2) = 2(b),(c),(d) |
| He II | 1640 | He II | He0→ He1+ | 24.59 | 1.81 | |||
| He II | 1640 | He II | He1+ recombination | 54.42 ( ⋆ ) | 4.00 ( ⋆ ) | |||
| O III | 1661,1666 | O III | O III]1 | O III]2 | O1+→ O2+ | 35.12 | 2.58 | f(O III1)/f(O III2) ≃ 0.7(c) |
| Si III | 1883,1892 | Si III | [Si III] | Si III] | Si1+→ Si2+ | 16.35 | 1.20 | f([Si III])/f(Si III]) ≲ 1.7(e) |
| C III | 1907,1909 | C III | [C III] | C III] | C1+→ C2+ | 24.38 | 1.79 | f([C III])/f(C III]) ≲ 1.6(e) |
Notes. The atom and emission line rest-frame wavelength for the UV lines studied here are provided in the first two columns. The short notation columns list the names used throughout this paper for the main lines or emission line doublets and their blue and red doublet components. The transition column provides that transitions for which the ionization energies are quoted in the column EIonization (Kramida et al. 2019; Leitherer et al. 2011). These energies correspond to the minimum required ionization energy needed to generate the respective emission lines. References for the expected emission line doublet component flux ratios presented in the last column are: (a)Torres-Peimbert & Pena (1984), (b)Martin & Wiese (1976), (c)Morton (1991), (d)Feibelman (1983), and (e)Osterbrock & Ferland (2006); Kewley et al. (2019a). ( † )The line profiles of N V and C IV are complicated by the fact that this emission is potentially a superposition of P Cygni profiles from stellar winds, emission from the ISM, and nebular emission. ( ⋆ )These energies correspond to the energy required to ionize the atom before electrons recombine with the atom to emit the emission line.
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