Looking at Radio-Quiet AGN with Radio Polarimetry

TL;DR

This study uses radio polarization and emission-line observations to investigate the dominant radio emission mechanisms in radio-quiet AGN, revealing interactions between outflows and surrounding gas that influence their radio properties.

Contribution

It demonstrates how combined radio polarization and emission-line studies can distinguish between jets, winds, and star formation as sources of radio emission in RQ AGN, providing new insights into their nature.

Findings

Detected composite jet and wind outflows in specific quasars.

Found anti-correlation between polarized radio emission and emission-line gas.

Suggested interaction between radio outflows and gaseous environment affects radio emission.

Abstract

The dominant radio emission mechanism in radio-quiet quasars (RQQs) is an open question. Primary contenders include: low-power radio jets, winds, star-formation and coronal emission. Our work suggests that radio polarization and emission-line studies can help to distinguish between these scenarios and determine the primary contributor. Our multi-frequency, multi-scale radio polarization study has revealed a composite jet and "wind" radio outflow in the radio-intermediate quasar, III Zw 2, as well as in the BALQSO, Mrk 231. Our radio polarization study in conjunction with the [O III] emission-line study of five type 2 RQQs have provided insights on the interplay of jets/winds and emission-line gas. These sources reveal an anti-correlation between polarized radio emission and [O III] emission. This is similar to that observed in some radio-loud AGN in the literature and suggests that the radio emission could be depolarized by the emission-line gas. Overall, our work suggests that a close interaction between the radio outflow and the surrounding gaseous environment is likely to be responsible for their stunted form in RQ and RI AGN.