Unveiling AGN Outflows: [O iii] Outflow Detection Rates and Correlation with Low-Frequency Radio Emission

TL;DR

This study explores the link between low-frequency radio emission and ionised gas outflows in AGN, revealing that radio detected AGN exhibit higher outflow rates and broader emission line components, suggesting a connection with AGN feedback mechanisms.

Contribution

It provides new evidence of a correlation between ionised outflows and low-frequency radio emission in AGN, highlighting the role of low-powered jets or shocks.

Findings

Radio detected AGN have a higher outflow rate (67.2%) than non-detected (44.6%).

Broad [O III] emission components are enhanced in radio detected AGN.

Most AGN do not show a radio excess driven by powerful jets.

Abstract

Some Active Galactic Nuclei (AGN) host outflows which have the potential to alter the host galaxy's evolution (AGN feedback). These outflows have been linked to enhanced radio emission. Here we investigate the connection between low-frequency radio emission using the International LOFAR Telescope and [O III] $\lambda$5007 ionised gas outflows using the Sloan Digital Sky Survey. Using the LOFAR Two-metre Sky Survey (LoTSS) Deep Fields, we select 198 AGN with optical spectra, 115 of which are detected at 144 MHz, and investigate their low-frequency radio emission properties. The majority of our sample do not show a radio excess when considering radio luminosity - SFR relationship, and are therefore not driven by powerful jets. We extract the [O III] $\lambda$5007 kinematics and remove AGN luminosity dependencies by matching the radio detected and non-detected AGN in $L_{\mathrm{6\mu m}}$ and redshift. Using both spectral fitting and $W_{80}$ measurements, we find radio detected AGN have a higher outflow rate (67.2$\pm$3.4 percent) than the radio non-detected AGN (44.6$\pm$2.7 percent), indicating a connection between ionised outflows and the presence of radio emission. For spectra where there are two components of the [O III] emission line present, we normalise all spectra by the narrow component and find that the average broad component in radio detected AGN is enhanced compared to the radio non-detected AGN. This could be a sign of higher gas content, which is suggestive of a spatial relationship between [O III] outflows and radio emission in the form of either low-powered jets or shocks from AGN winds.