The Detection Rate of Associated \mgii\ Absorption Lines in Quasars Depends on Their Radio Emission

TL;DR

This study shows that the likelihood of detecting ext{MgII} absorption lines in quasars increases with their evolutionary stage, especially in older, non-peaked radio spectrum quasars, due to jet-driven feedback expelling gas.

Contribution

It provides the first large-scale statistical analysis linking quasar radio spectral evolution to the incidence of associated ext{MgII} absorption lines, highlighting jet feedback effects.

Findings

Evolved quasars have a 1.7 times higher incidence of ext{MgII} absorbers than young sources.

Non-peaked radio spectrum quasars show significantly more ext{MgII} absorption lines.

Jet-driven feedback expels gas, increasing absorption line coverage in older quasars.

Abstract

In active galactic nuclei, jet-driven feedback plays a significant role in influencing the properties of gas within their host galaxy and the circumgalactic medium. By combining observations from the Very Large Array Sky Survey, the Faint Images of the Radio Sky at Twenty-cm, the LOFAR Two Metre Sky Survey, and the Sloan Digital Sky Survey, we assembled a sample of 3,141 radio-loud quasars, among which 418 exhibit \mgii\ associated absorption lines in their Sloan spectra. We classify these quasars into evolutionary stages based on their radio spectral shapes. Our analysis reveals that evolved quasars exhibit a significantly higher incidence of \mgii\ associated absorption lines compared to younger sources, particularly among quasars with ``non-peaked'' radio spectra, which show an incidence of \mgii\ associated absorbers approximately 1.7 times greater than that of gigahertz-peaked spectrum sources. This observation can be explained effectively by jet-driven feedback. As quasars age, their jets expand and expel substantial amounts of gas from small scales to larger scales, ultimately reaching the circumgalactic medium. The gas expelled from the inner regions and distributed over larger scales results in a greater coverage fraction of absorbing gas. Consequently, evolved quasars exhibit a higher incidence of \mgii\ absorption lines.