Looking for Signatures of AGN Feedback in Radio-Quiet AGN

In this article, we discuss the state of AGN feedback in radio-quiet (RQ) AGN. This study involves heterogeneous samples of nearby Seyfert and LINER galaxies as well as quasi-stellar objects (QSOs) that have been observed at low radio frequencies (few similar to 100 MHz) with the upgraded Giant Meterwave Radio Telescope (GMRT) and similar to GHz frequencies with the Karl G. Jansky Very Large Array (VLA) and Very Long Baseline Array (VLBA). These multi-frequency, multi-resolution observations detect a range of arcsecond-scale radio spectral indices that are consistent with the presence of multiple contributors including starburst winds and AGN jets or winds; steep spectrum relic emission is observed as well. Polarization-sensitive data from the VLA and GMRT suggest that the radio outflows are stratified (e.g., in IIIZw2, Mrk231); distinct polarization signatures suggest that there could either be a spine + sheath structure in the radio outflow, or there could be a jet + wind structure. Similar nested biconical outflows can also explain the VLBA and SDSS emission-line data in the KISSR sample of double-peaked emission-line Seyfert and LINER galaxies. Furthermore, the modeling of the emission-lines with plasma modeling codes such as MAPPINGS indicates that parsec-scale jets and winds in these sources can disturb or move the narrow-line region (NLR) gas clouds via the shock + precursor mechanism. Apart from the presence of relic emission, several Seyfert and LINER galaxies show clear morphological signatures of episodic jet activity. In one such source, NGC2639, at least four distinct episodes of jets are observed, the largest one of which was only detectable at 735 MHz with the GMRT. Additionally, a similar to 6 kpc hole in the CO molecular gas along with a dearth of young stars in the center of its host galaxy is observed. Multiple jet episodes on the 10-100 parsec scales and a similar to 10 parsec hole in the molecular gas is also observed in the Seyfert galaxy NGC4051. This suggests a link between episodic jet activity in RQ AGN and AGN feedback influencing the evolution of their host galaxies. However, a similar simple relationship between radio outflows and molecular gas mass is not observed in the Palomar-Green (PG) QSO sample, indicating that AGN feedback is a complex phenomenon in RQ AGN. AGN feedback must occur through the local impact of recurring multi-component outflows in RQ AGN. However, global feedback signatures on their host galaxy properties are not always readily evident.

Automated summary

In this article, the authors discuss the state of AGN feedback in radio-quiet (RQ) AGN. They use observations from GMRT, VLA, and VLBA to study nearby Seyfert and LINER galaxies as well as QSOs. The results show a range of radio spectral indices and suggest the presence of multiple contributors including starburst winds and AGN jets or winds.