Mergers Do Trigger AGNs out to z $\sim$ 0.6
  Aims. The fueling and feedback of Active Galactic Nuclei (AGNs) are important
in understanding the co-evolution between black holes and host galaxies.
Mergers are thought to have the capability to bring gas inwards and ignite
nuclear activity, especially for more powerful AGNs. However, there is still
significant ongoing debate on whether mergers can trigger AGNs and, if they do,
whether mergers are a significant triggering mechanism. Methods. We select a
low-redshift ($0.005<z<0.1$) sample from the Sloan Digital Sky Survey (SDSS)
and a high-redshift ($0 < z < 0.6$) sample from the Galaxy And Mass Assembly
(GAMA) survey. We take advantage of the convolutional neural network technique
to identify mergers. We use mid-infrared (MIR) color cut and optical emission
line diagnostics to classify AGNs. We also include Low Excitation Radio
Galaxies (LERGs) to investigate the connection between mergers and low
accretion rate AGNs. Results. We find that AGNs are more likely to be found in
mergers than non-mergers, with an AGN excess up to $1.81\pm{0.16}$, suggesting
that mergers can trigger AGNs. We also find the fraction of mergers in AGNs is
higher than that in non-AGN controls, for both MIR and optically selected AGNs,
as well as LERGs, with values between $16.40\pm{0.5}\%$ and $39.23\pm{2.10}\%$,
implying a non-negligible to potentially significant role of mergers in
triggering AGNs. This merger fraction in AGNs increases as stellar mass
increases which supports the idea that mergers are more important for
triggering AGNs in more massive galaxies. In terms of merger fraction as a
function of AGN power we find a positive trend for MIR selected AGNs and a
complex trend for optically selected AGNs, which we interpret under an
evolutionary scenario proposed by previous studies. In addition, obscured MIR
selected AGNs are more likely to be hosted in mergers than unobscured MIR
selected AGNs.
