Radio Emission and AGN Feedback in Post-starburst Galaxies

TL;DR

This study examines radio-mode AGN activity in post-starburst galaxies to assess its role in halting star formation, finding that such activity likely occurs after the starburst ends and is linked to older stellar populations.

Contribution

It provides evidence that radio AGN activity in post-starburst galaxies is triggered post-starburst and is not responsible for quenching star formation.

Findings

Radio AGN activity is observed in 12 out of 513 galaxies.

Radio activity is not correlated with recent star formation.

Radio luminosity correlates with total stellar mass, not recent star formation.

Abstract

We investigate radio-mode AGN activity among post-starburst galaxies from the Sloan Digital Sky Survey to determine whether AGN feedback may be responsible for the cessation of star formation. Based on radio morphology and radio-loudness from the FIRST and NVSS data, we separate objects with radio activity due to an AGN from ongoing residual star formation. Of 513 SDSS galaxies with strong A-star spectra, 12 objects have 21-cm flux density above 1 mJy. These galaxies do not show optical AGN emission lines. Considering that the lifetime of radio emission is much shorter than the typical time-scale of the spectroscopic features of post-starburst galaxies, we conclude that the radio-emitting AGN activity in these objects was triggered after the end of the recent starburst, and thus cannot be an important feedback process to explain the post-starburst phase. The radio luminosities show a positive correlation with total galaxy stellar mass, but not with the mass of recently formed stars. Thus the mechanical power of AGN feedback derived from the radio luminosity is related to old stellar populations dominating the stellar mass, which in turn are related to the masses of central supermassive black holes.