Environment or Outflows? New insight into the origin of narrow associated QSO absorbers

TL;DR

This study analyzes the velocity distribution of MgII narrow absorption lines in quasar spectra, revealing high-velocity outflows and differences between radio-loud and radio-quiet quasars, providing insights into quasar feedback mechanisms.

Contribution

It presents new large-scale analysis of MgII NALs with improved redshift estimates, identifying high-velocity outflows and differences based on radio properties, advancing understanding of quasar feedback.

Findings

High-velocity MgII NALs extend to at least 6000 km/s from QSOs.

Significant excess of low-velocity MgII NALs in radio-loud QSOs.

Evidence suggests gas expulsion and heating in quasar environments.

Abstract

Recent detailed studies of Narrow Absorption Line (NAL) systems in QSO-spectra have revealed that at least 50% of QSOs have NALs associated with the central engine, and in most cases they are found to be outflowing. Will studies of NALs provide the much sort after evidence for ubiquitous QSO feedback that can halt the formation of stars in galaxies? I present new results on the distribution of line-of-sight velocity offsets between MgII absorbers and their background QSOs, based on a large catalogue of absorbers from SDSS DR6 and greatly improved QSO-redshift estimates. My analysis reveals a high-velocity population of MgII NALs extending out to at least 6000 km/s from the QSOs, which cannot be ascribed to the clustering of local galaxies, similar to that observed recently for CIV absorbers. The very existence of such low ionisation gas clouds in the intense ionising field of the QSO suggests that we may indeed be witnessing the mechanical expulsion of gas, alongside the heating previously observed. I also show that there is a significant excess of low-velocity MgII NALs in radio-loud QSOs compared to radio-quiet QSOs. In the near future, improved QSO clustering results will allow us to say whether this is due to environmental or feedback effects.