Comparing metallicity correlations in nearby non-AGN and AGN-host galaxies

TL;DR

This study examines how active galactic nuclei (AGN) affect the spatial distribution of gas-phase metallicity in galaxies, revealing that AGN-host galaxies have shorter metallicity correlation lengths primarily due to reduced star formation rates.

Contribution

Introduces a Bayesian method for measuring metallicity that accounts for AGN contributions and compares metallicity correlations in AGN-host and non-AGN galaxies within a unified framework.

Findings

AGN-host galaxies have smaller metallicity correlation lengths than non-AGN galaxies at fixed stellar mass.

Star formation rate is more fundamental than stellar mass in determining metallicity correlation length.

Both SFR and stellar mass positively correlate with metallicity correlation length.

Abstract

The gas-phase metallicity distribution within galaxies records critical information about galactic evolution. In this work we investigate how active galactic nuclei (AGN) influence this distribution by measuring the two-point correlation functions of gas-phase metallicity in 95 non-AGN and 37 AGN-host galaxies from the Calar Alto Legacy Integral Field spectroscopy Area integral field spectrographic survey. We measure metallicity using a novel Bayesian method that properly includes both stellar and AGN contributions to emission line fluxes and allows us to measure metallicities in both AGN-host and non-AGN galaxies in a single, consistent framework. We find that the two-point correlation functions of both AGN-host and non-AGN galaxies are well-fit by a simple injection-diffusion model, and that the correlation lengths $l_\mathrm{corr}$ we derive for the non-AGN galaxies are reasonably consistent with those obtained in earlier work. The AGN-host galaxies generally have smaller $l_\mathrm{corr}$ than non-AGN galaxies at fixed stellar mass, but similar $l_\mathrm{corr}$ at fixed star formation rate (SFR), suggesting that the primary effect of hosting an AGN in this sample is a reduction in SFR at fixed stellar mass, and that this in turn suppresses the correlation length. Our findings further indicate that, while both SFR and stellar mass are positively correlated with metallicity correlation length $l_\mathrm{corr}$, the former is more fundamental, implying that fluctuations in the metallicity distribution within galaxies are driven more by short-term responses to physical processes such as star formation that can change much faster than a Hubble time.