Galaxy Zoo: Are Bars Responsible for the Feeding of Active Galactic Nuclei at 0.2 < z < 1.0?

TL;DR

This study investigates whether large-scale bars in galaxies at 0.2<z<1.0 are responsible for fueling active galactic nuclei (AGN), finding no significant correlation between bars and AGN activity, thus challenging the idea that bars are primary AGN fuelers.

Contribution

The paper introduces a novel comparison method showing that large-scale bars do not significantly enhance AGN activity at intermediate redshifts, extending previous local universe findings.

Findings

No significant difference in bar fraction between AGN and inactive galaxies.

Bar fraction cannot be more than twice as high in AGN hosts with 99.7% confidence.

Large-scale bars are unlikely to be the main fueling mechanism for AGN since z=1.

Abstract

We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS, COSMOS, and GOODS-S surveys to create samples of face-on, disc galaxies at 0.2 < z < 1.0. We use a novel method to robustly compare a sample of 120 AGN host galaxies, defined to have 10^42 erg/s < L_X < 10^44 erg/s, with inactive control galaxies matched in stellar mass, rest-frame colour, size, Sersic index, and redshift. Using the GZH bar classifications of each sample, we demonstrate that AGN hosts show no statistically significant enhancement in bar fraction or average bar likelihood compared to closely-matched inactive galaxies. In detail, we find that the AGN bar fraction cannot be enhanced above the control bar fraction by more than a factor of two, at 99.7% confidence. We similarly find no significant difference in the AGN fraction among barred and non-barred galaxies. Thus we find no compelling evidence that large-scale bars directly fuel AGN at 0.2<z<1.0. This result, coupled with previous results at z=0, implies that moderate-luminosity AGN have not been preferentially fed by large-scale bars since z=1. Furthermore, given the low bar fractions at z>1, our findings suggest that large-scale bars have likely never directly been a dominant fueling mechanism for supermassive black hole growth.