A Mini-BAL Outflow at 900 pc from the Central Source: VLT/X-shooter Observations

TL;DR

This study uses high-quality VLT/X-shooter spectra to analyze a mini-BAL quasar, determining the physical conditions and location of the outflowing gas at approximately 900 parsecs from the central black hole.

Contribution

It provides the first detailed physical and spatial characterization of a mini-BAL outflow at this distance using combined ionization and density diagnostics.

Findings

Outflow velocity range: -1500 to -3000 km/s.

Hydrogen column density: log(N_H) ≈ 21.47.

Distance of outflow from central source: ~880 pc.

Abstract

We determine the physical conditions and location of the outflow material seen in the mini-BAL quasar SDSS J1111+1437 (z = 2.138). These results are based on the analysis of a high S/N, medium-resolution VLT/X- shooter spectrum. The main outflow component spans the velocity range -1500 to -3000 km s$^{-1}$ and has detected absorption troughs from both high-ionization species: C IV , N V , O VI , Si IV , P V , and S IV ; and low-ionization species: H I , C II , Mg II , Al II , Al III , Si II , and Si III . Measurements of these troughs allow us to derive an accurate photoionization solution for this absorption component: a hydrogen column density, log ( N H ) = 21.47 $^{+0.21}_{-0.27}$ cm$^{-2}$ and ionization parameter, log (U_H) = -1.23$^{+0.20}_{-0.25}$. Troughs produced from the ground and excited states of S IV combined with the derived U_H value allow us to determine an electron number density of log (n_e) = 3.62$^{+0.09}_{-0.11}$ cm$^{-3}$ and to obtain the distance of the ionized gas from the central source: R = 880$^{+220}_{-260}$ pc.