A Radio Polarimetric Study to Disentangle AGN Activity and Star-Formation in Seyfert Galaxies

TL;DR

This study uses radio polarimetric observations to distinguish between star formation and AGN activity in Seyfert galaxies, revealing jet-related origins of radio emission and episodic AGN activity.

Contribution

It provides new insights into the origins of radio emission in Seyfert galaxies through detailed polarization and morphological analysis, highlighting the role of jets and AGN activity.

Findings

Seyfert galaxies show lobe/bubble-like radio features

Starburst galaxies' radio emission coincides with star-forming regions

Seyferts tend to have more polarized radio structures

Abstract

To understand the origin of radio emission in radio-quiet AGN and differentiate between the contributions from star formation, AGN accretion, and jets, we have observed a nearby sample of Seyfert galaxies along with a comparison sample of starburst galaxies using the EVLA in full-polarization mode in the B-array configuration. The radio morphologies of the Seyfert galaxies show lobe/bubble-like features or prominent cores in radio emission whereas the starburst galaxies show radio emission spatially coincident with the star-forming regions seen in optical images. There is tentative evidence that Seyferts tend to show more polarized structures than starburst galaxies at the resolution of our observations. We find that unlike a sample of Seyfert galaxies hosting kilo-parsec scale radio (KSR) emission, starburst galaxies with superwinds do not show radio-excess compared to the radio-FIR correlation. This suggests that shock acceleration is not adequate to explain the excess radio emission seen in Seyferts and hence most likely have a jet-related origin. We also find that the [O III] luminosity of the Seyferts is correlated with the off-nuclear radio emission from the lobes, whereas it is not well correlated with the total emission which also includes the core. This suggests strong jet-medium interaction, which in turn limits the jet/lobe extents in Seyferts. We find that the power contribution of AGN jet, AGN accretion, and star formation is more or less comparable in our sample of Seyfert galaxies. We also find indications of episodic AGN activity in many of our Seyfert galaxies.