Testing the role of AGN on the star formation and metal enrichment of "twin galaxies"

TL;DR

This study investigates how active galactic nuclei (AGN) influence star formation and chemical enrichment by comparing twin galaxy pairs with and without AGN, revealing that AGN hosts tend to have older, more metal-rich stellar populations.

Contribution

It introduces a twin galaxy comparison method to isolate AGN effects on galaxy evolution, providing new insights into their impact on stellar populations and chemical enrichment histories.

Findings

AGN galaxies are more evolved than their non-AGN twins 90% of the time.

AGN hosts are older and more metal-rich than non-AGN counterparts.

Differences between twin galaxies are statistically significant.

Abstract

We explore the effect of AGN activity on the star formation history of galaxies by analysing the stellar population properties of ten pairs of nearby twin galaxies -- selected as being visually similar except for the presence of an AGN. The selection of such twin samples represents a method to study AGN feedback, as recently proposed by del Moral Castro et al. We use integral field unit (IFU) data from CALIFA, stacked within three fixed apertures. AGN galaxies in a twin pair suggest more evolved stellar populations than their non-AGN counterpart 90% of the time, regardless of aperture size. A comparison with a large sample from SDSS confirms that most twins are representative of the general population, but in each twin the differences between twin members is significant. A set of targeted line strengths reveal the AGN member of a twin pair is older and more metal rich than the non-AGN galaxy, suggesting AGN galaxies in our sample may either have an earlier formation time or follow a different star formation and chemical enrichment history. These results are discussed within two simple, contrasting hypotheses for the role played by AGN in galaxy evolution, which can be tested in the future at a greater detail with the use of larger data sets.