A comparative study of radio signatures from winds and jets: Modelling synchrotron emission and polarization

TL;DR

This study models and compares the radio emission and polarization signatures of AGN winds and jets through simulations, providing observational criteria to distinguish between these outflow mechanisms.

Contribution

It introduces detailed simulations of magnetized winds and analyzes their radio signatures, highlighting differences from jets and the importance of resolution in observations.

Findings

Winds show broader, hourglass-shaped emission regions unlike jets' thin spines.

Observable features depend on wind power, density, and viewing angle.

High resolution is crucial to distinguish wind and jet emission features.

Abstract

Outflows driven by active galactic nuclei (AGN) are seen in numerous compact sources; however, it has remained unclear how to distinguish between the driving mechanisms, such as winds and jets. Therefore, our study aims to offer observational insights from simulations to aid in this distinction. Specifically, in this paper, we investigate the evolution of wide-angled, moderately relativistic, magnetized winds and analyze their non-thermal radio emission and polarization properties. We find that the evolution of winds varies depending on factors such as power, density, and opening angle, which in turn influence their observable characteristics. Additionally, different viewing angles can lead to varying observations. Furthermore, we note distinctions in the evolution of winds compared to jets, resulting in disparities in their observable features. Jets typically exhibit a thin spine and hotspot(s). Winds manifest broader spines or an "hourglass-shaped" bright emission in the cocoon, which are capped by bright arcs. Both display high polarization coinciding with the bright spine and hotspots/arcs, although these regions are relatively compact and localized in jets when compared to winds. We emphasize the importance of high resolution, as we demonstrate that emission features from both jets and winds can become indistinguishable at lower resolutions. The distribution of polarization is largely unaffected by resolution, though lower polarization becomes more noticeable when the resolution is decreased.