Table 3.
Definitions of ISM phases(a) and their respective gas temperature and hydrogen abundance ranges.
| ISM phase definition | Abbreviation | Temperature [K] | Hydrogen abundance |
|---|---|---|---|
| Hot Ionised Medium | HIM | T > 5 × 105 | – |
| Warm-Hot Ionised Medium | WHIM | 3.5 × 104 < T < 5.0 × 105 | – |
| Warm Collisionally Ionised Medium | WCIM | 1.5 × 104 < T < 3.5 × 104 | χHII > 0.5 |
| Warm Photoionised Medium | WPIM | 6.0 × 103 < T < 1.5 × 104 | χHII > 0.5 |
| Warm Neutral Medium | WNM | 6.0 × 103 < T < 3.5 × 104 | χHI > 0.5 |
| Warm Ionised Medium | WIM | T < 6.0 × 103 | χHII > 0.5 |
| Unstable Neutral Medium | UNM | 5.0 × 102 < T < 6.0 × 103 | χHI > 0.5 |
| Cold Neutral Medium | CNM | T < 5.0 × 102 | χHI > 0.5 |
| Cold Molecular Medium | UMM | T < 6.0 × 103 | χH2 > 0.25 |
Notes. Hydrogen abundances are obtained according to the relation: χHI = 1 − 2χH2 − χHII, meaning that χH2 = 0.5 for gas cells where all of the hydrogen is in molecular form.
Adopted from Kim et al. (2023b), with the difference that we use the term ‘warm ionised medium’ for what they call ‘unstable ionised medium’.
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