Table 4
Photoionization models.
| COS | STIS |
 a
|
||||||||
| AOD | PC | AOD | PC | |||||||
| Trough | log UH | log NH | log UH | log NH | log UH | log NH | log UH | log NH | C iv | N v |
| (cm-2) | (cm-2) | (cm-2) | (cm-2) | |||||||
|
|
||||||||||
| T1 | –1.1 | 18.5 | –1.5 | 18.5 | –1.2 | 18.3 | –1.5 | 18.4 | –0.51 | –0.17 |
| T2 | –1.4 | 18.8 | –1.4 | 18.9 | –1.4 | 18.9 | –1.3 | 19.0 | –0.55 | –0.28 |
| T3 | –1.2 | 18.4 | –1.2 | 18.6 | –1.3 | 18.4 | –1.1 | 18.7 | –0.57 | –0.35 |
| T4 | –1.1 | 18.6 | –1.1 | 18.6 | –1.2 | 18.5 | –1.2 | 18.6 | –0.60 | –0.41 |
| T5(high)b | –1.0 | 19.2 | –1.1 | 19.2 | –1.1 | 19.1 | –1.1 | 19.2 | –0.62 | –0.48 |
| T5(low) | –1.6 | 18.6 | –1.5 | 18.2 | –1.8 | 18.4 | –1.5 | 18.2 | –0.41 | +0.26 |
| T6 | –0.9 | 18.6 | –0.9 | 18.6 | –0.9 | 18.5 | –0.9 | 18.8 | –0.68 | –0.56 |
| T7c | –0.5 | 19.2 | ··· | ··· | –0.8 | 18.8 | ··· | ··· | –0.72 | –0.59 |
|
|
||||||||||
| Total NH | ··· | 19.8 | ··· | 19.6 | ··· | 19.6 | ··· | 19.7 | ||
Notes. Troughs T8 and T9 have heavy blending in the blue component of C iv, and the red component of C iv is very weak. We therefore do not include ionization analysis of these troughs.
Fractional changes in column density expected if the number density were high enough for the absorber to be in equilibrium at the time of the COS observations (see Sect. 3)
Lower limits. Summation of low and high ionization components for trough T5 overpredicts C iv by a factor of 2, which is ameliorated by increasing UH of the high ionization component. Since all of the C iv comes from the low ionization component, we use the lower ionization parameter to compute lower limits on the distance for this trough (see Sect. 3).
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