The Properties of Low-Redshift FeLoBAL Quasars: III. The Location and Geometry of the Outflows

TL;DR

This study investigates the properties, locations, and geometries of outflows in low-redshift FeLoBAL quasars, revealing correlations with accretion rates, outflow velocities, and emission features, and proposing different mechanisms for various quasar types.

Contribution

It provides new insights into the relationship between outflow velocities, accretion rates, and outflow locations, and explores the connection between BAL outflows and [O III] emission in FeLoBAL quasars.

Findings

High-velocity outflows are found at parsec scales in high accretion rate quasars.

Outflow velocity correlates with Eddington ratio, with scatter linked to launch radius.

[O III] emission properties depend on BAL location and Seyfert type, with hidden broad components in some cases.

Abstract

We present continued analysis of a sample of low-redshift iron low-ionization broad absorption-line quasars (FeLoBALQs). Choi et al. (2022) presented $SimBAL$ spectral analysis of BAL outflows in 50 objects. Leighly et al. (2022) analyzed optical emission lines of 30 of those 50 objects and found that they are characterized by either a high accretion rate ($L_\mathrm{Bol}/L_\mathrm{Edd}>0.3$) or low accretion rate ($0.03<L_\mathrm{Bol}/L_\mathrm{Edd}<0.3$). We report that the outflow velocity is inversely correlated with the BAL location among the high accretion rate objects, with the highest velocities observed in the parsec-scale outflows. In contrast, the low Eddington ratio objects showed the opposite trend. We confirmed the known relationship between outflow velocity and $L_\mathrm{Bol}/L_\mathrm{Edd}$, and found that the scatter plausibly originates in the force multiplier (launch radius) in the low (high) accretion rate objects. A log volume filling factor between $-6$ and $-4$ was found in most outflows, but was as high as $-1$ for low-velocity compact outflows. We investigated the relationship between the observed [O III] emission and that predicted from the BAL gas. We found that these could be reconciled if the emission-line covering fraction depends on Seyfert type and BAL location. The difference between the predicted and observed [O III] luminosity is correlated with the outflow velocity, suggesting that [O III] emission in high Eddington ratio objects may be broad and hidden under Fe II emission. We suggest that the physical differences in the outflow properties as a function of location in the quasar and accretion rate point to different formation, acceleration, and confinement mechanisms for the two FeLoBALQ types.