Merger-AGN connection in the NW-2 field

We first investigate the merger-AGN connection using a binary AGN/non-AGN classification. We observe a clear AGN excess (a factor of 2-3) in mergers with respect to non-mergers for the MIR AGNs, and a mild excess for the X-ray and SED AGNs, indicating that mergers could trigger all three types but are more connected with the MIR AGNs. About half of the MIR AGNs are in mergers but it is unclear whether mergers are the main trigger.

For the X-ray and SED AGNs, mergers are unlikely to be the dominant triggering mechanism. We also explore the connection using the continuous AGN fraction f_AGN_ parameter. Mergers exhibit a clear excess of high f_AGN_ values relative to non-mergers, for all AGN types.

We unveil the first merger fraction f_merger_-f_AGN_ relation with two distinct regimes. When the AGN is not very dominant, the relation is only mildly increasing or even flat, with the MIR AGNs showing the highest f_merger_. In the regime of very dominant AGNs (f_AGN_>=0.8), f_merger_ shows the same steeply rising trend with increasing f_AGN_ for all AGN types.

These trends are also seen when plotted against AGN bolometric luminosity. We conclude that mergers are most connected with dust-obscured AGNs (generally linked to a fast-growing phase of the supermassive black hole) and are the main or even the sole fuelling mechanism of the most powerful AGNs.