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03 May 2024 |
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Evidence for Fluorescent Fe II Emission from Extended Low Ionization Outflows in Obscured Quasars | | Tinggui Wang
; Gary Ferland
; Chenwei Yang
; Huiyuan Wang
; Shaohua Zhang
; | | Date: |
1 Sep 2016 | | Abstract: | Recent studies have shown that outflows in at least some broad absorption
line (BAL) quasars are extended well beyond the putative dusty torus. Such
outflows should be detectable in obscured quasars. We present four WISE
selected infrared red quasars with very strong and peculiar ultraviolet Fe ii
emission lines: strong UV Fe II UV arising from transitions to ground/low
excitation levels, and very weak Fe II at wavelengths longer than 2800 {AA}.
The spectra of these quasars display strong resonant emission lines, such as C
IV, Al III and Mg II but sometimes, a lack of non-resonant lines such as C
III], S III and He II. We interpret the Fe II lines as resonantly scattered
light from the extended outflows that are viewed nearly edge-on, so that the
accretion disk and broad line region are obscured by the dusty torus, while the
extended outflows are not. We show that dust free gas exposed to strong
radiation longward of 912 {AA} produces Fe II emission very similar to that
observed. The gas is too cool to collisionally excite Fe II lines, accounting
for the lack of optical emission. The spectral energy distribution from the UV
to the mid-infrared can be modeled as emission from a clumpy dusty torus, with
UV emission being reflected/scattered light either by the dusty torus or the
outflow. Within this scenario, we estimate a minimum covering factor of the
outflows from a few to 20% for the Fe II scattering region, suggesting that Fe
II BAL quasars are at a special stage of quasar evolution. | | Source: | arXiv, 1609.0064 | | Services: | Forum | Review | PDF | Favorites | |
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