  Galaxy mergers play a crucial role in the formation of massive galaxies and
the buildup of their bulges. An important aspect of the merging process is the
in-spiral of the supermassive black-holes (SMBHs) to the centre of the merger
remnant and the eventual formation of a SMBH binary. If both the SMBHs are
accreting they will form a dual or binary active galactic nucleus (DAGN). The
final merger remnant is usually very bright and shows enhanced star formation.
In this paper we summarize the current sample of DAGN from previous studies and
describe methods that can be used to identify strong DAGN candidates from
optical and spectroscopic surveys. These methods depend on the Doppler
separation of the double peaked AGN emission lines, the nuclear velocity
dispersion of the galaxies and their optical/UV colours. We describe two high
resolution, radio observations of DAGN candidates that have been selected based
on their double peaked optical emission lines (DPAGN). We also examine whether
DAGN host galaxies have higher star formation rates (SFRs) compared to merging
galaxies that do not appear to have DAGN. We find that the SFR is not higher
for DAGN host galaxies. This suggests that the SFRs in DAGN host galaxies is
due to the merging process itself and not related to the presence of two AGN in
the system.
