Post-starburst--AGN Connection: Spatially Resolved Spectroscopy of Hdelta-Strong AGNs

Abstract

Ever since the co-existence of an active galactic nucleus (AGN) and a starburst was observationally discovered, there has been a significant controversy over whether there is a physical connection between starbursts and AGNs. If yes, it is a subject of interest to reveal which one triggers another. Here we bring a unique insight onto the subject by identifying 840 galaxies with both a post-starburst signature (strong Balmer absorption lines) and an AGN (based on the emission line ratio). These poststarburst-AGNs account for the 4.2% of all the galaxies in a volume-limited sample. The presence of a post-starburst phase with an active AGN itself is of importance, suggesting that AGNs may outlive starbursts in the starburst-AGN connection. In addition, we have performed spatially resolved spectroscopy of three of our poststarbusrst-AGN galaxies, obtaining some evidence that the post-starburst region is more extended, but sharply centred around the central AGN, confirming a spatial connection between the post-starburst and the AGN.