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The Physical Properties and Energetics of FeLoBAL Quasar Outflows

Published onJun 01, 2020
The Physical Properties and Energetics of FeLoBAL Quasar Outflows

Quasar outflows can carry a significant amount of energy and mass from the active galactic nuclei (AGNs) to their host galaxies. They are frequently seen as blueshifted broad absorption lines (BALs) in the rest-UV quasar spectra and are considered to be one of the main drivers of the quasar feedback/evolution. Despite a long history and the rich data sets currently available, only a handful of BAL quasar (BALQ) spectra have been analyzed in detail. This is mainly because the BALQ spectra are challenging to analyze, especially when they show severe line blending.We present the first systematic study of a moderate-sized sample of FeLoBALQs using the spectral-synthesis code SimBAL (Leighly et al. 2018). FeLoBALQs are a subset of BALQs with the highest column density outflows that show absorption lines from the Fe II and other low-ionization ions. They are mostly dust-reddened and are believed to be in a short-lived “blow-out” phase of quasar evolution. SimBAL’s forward modeling method allowed us to extract the physical properties of the outflowing gas in all the objects in the sample, including the most heavily absorbed ones that show significant line blending of thousands of Fe II transitions.From the sample of 26 FeLoBALQs we found the outflows have a wide range of ionization parameter values, log U ~ -4 to 1.5 and densities, log n ~ 3 to 8 (cm-3). The sample contains a variety of FeLoBALQ spectral morphologies with varying degrees of absorption strengths. Anomalous reddening (Choi et al. 2020) was required for nine objects where the steep reddening was only found at short wavelengths. We also found a wide range of outflow locations ranging from parsec to kilo-parsec scales. Eleven objects have outflows that are estimated to have enough energy for quasar feedback (E>0.005LBol). We identified a previously reported correlation between the strength of the outflow and the bolometric luminosity. This study demonstrates the feasibility of statistical analysis of large samples of FeLoBALQs using SimBAL.

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