Tracking Outflow using Line-Locking (TOLL). II. Large Line-Locking Web identified in Quasar J151352+085555

TL;DR

This paper reports the discovery of one of the largest known line-locking webs in quasar outflows, revealing complex cloud interactions and emphasizing the role of radiative acceleration in shaping quasar winds.

Contribution

It presents the identification and analysis of an extensive line-locking web in quasar J151352+085555, including detailed photoionization modeling and statistical insights into cloud properties.

Findings

12 absorption line systems identified

10 out of 12 absorbers are line-locked

Cloud metallicities are likely sub-solar

Abstract

Quasar outflows often consist of two clouds with velocity separations matching the doublet spacings of common UV resonance transitions, a phenomenon known as line-locking, which is commonly observed in quasar spectra. Multiple clouds can be locked together through multi-ion doublets, forming 'line-locking web'. In the second paper of the TOLL project, we present discovery of one of the largest 'line-locking web' known to date from the VLT/UVES spectra of QSO J151352+085555. We identify 12 associated narrow absorption line systems through the C IV, N V, Si IV, O VI, and multiple Lyman lines (Ly${\alpha}$ to Ly${\epsilon}$), and find 10 out of the 12 absorbers are line-locked together by comparing velocity separations between different absorption systems. By conducting photoionization modeling with CLOUDY, we measure the total hydrogen column densities, metallicities, and ionization parameters of these absorbers, which suggests the absorbers likely have sub-solar metallicities. A preliminary statistical analysis demonstrates the shadowed clouds tend to have similar ionization states comparing to the shadowing ones. Identification of one of the largest line-locking webs implies that radiative acceleration plays an important role in sorting out cloud velocities in quasar outflows, and highlights the need for more sophisticated theoretical models to explain its formation and evolution.