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Exploring the Link between Broad-Absorption-Line Outflows and [OIII] Emission in Low-Redshift FeLoBAL Quasars

Published onJun 01, 2020
Exploring the Link between Broad-Absorption-Line Outflows and [OIII] Emission in Low-Redshift FeLoBAL Quasars

Black hole-galaxy feedback is an established ingredient in cosmological structure formation simulations, but the form of that feedback is not known. Among the candidates for quasar-mode feedback are broad absorption line (BAL) outflows and ionized emission-line outflows. These phenomena are found at similar distances from the central engine (parsecs to kiloparsecs), and they are both powered by photoionization of gas with similar physical conditions. It is conceivable that they are manifestations of the same outflowing gas, with the difference being that BAL quasar outflows are observed in the line of sight. There are, however, a number of reasons why no direct relationship would be detectable. For example, there could be additional outflows or stationary gas not in the line of sight that would contribute to the [OIII] emission without being detected as a BAL. In addition, large outflow velocities would produce extremely broad emission lines that blend with the continuum. We investigated the relationship between BAL outflows and low-ionization emission-line properties in a sample of 25 FeLoBAL quasars. The redshifts of the objects in this unique sample were chosen so that both the [OIII] emission lines and FeII and MgII absorption lines appear in a single Sloan Digital Sky Survey spectrum. We modeled the FeLoBAL absorption using the spectral-synthesis code SimBAL, and used the results to predict the [OIII] emission from the BAL gas. The predicted and observed [OIII] emission were found to be loosely correlated for the subset of objects with similar emission- and absorption-line kinematics, and when a radius-dependent covering fraction and a projection correction factor for the outflow velocity were included.

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