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| Paper: |
Probing High-Column Outflows in BALQSOs Using Metastable Helium |
| Volume: |
460, AGN Winds in Charleston |
| Page: |
72 |
| Authors: |
Leighly, K. M.; Lucy, A. B.; Dietrich, M.; Terndrup, D.; Gallagher, S. C. |
| Abstract: |
Outflows are believed to be ubiquitous and fundamentally important in
active galaxies. Despite their importance, key physical properties of
outflows remain poorly unconstrained; this severely limits study of the
acceleration process. It is especially difficult to
constrain the column density since most of the lines are
saturated. However, column densities can be measured using ions that
are expected to be relatively rare in the gas, since they are least
likely to be saturated. Phosphorus, specifically the P V
doublet at 1118 and 1128Å, is generally regarded as a useful
probe of high column densities because of its low abundance. We have
found that the metastable neutral helium triplet is an equally
valuable probe of high column densities in BALQSOs. The significant
advantage is that it can be observed in the infrared (He I*λ 10830) and the optical (He I*λ 3888)
bands from the ground in low-redshift (z < 1.2) objects.
We report the discovery of the first He I*λ 10830 BALQSO
FBQS J1151+3822, and discuss constraints on the column density
obtained from the optical and IR He I* lines. In addition, a
new observation revealing Mg II and Fe II absorption
provides further constraints, and Cloudy modeling of
He I*, Mg II and Fe II suggests that the
difference between LoBALs and FeLoBALs is column density along the
line of sight. |
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