A Multi-wavelength Study of the Dual Nuclei in Mrk 212
  We present radio observations of the galaxy merger remnant Mrk 212 with the
Karl G. Jansky Very Large Array (VLA) and the upgraded Giant Meter Radio
Telescope (uGMRT). Mrk 212 has two previously known radio sources associated
with the two optical nuclei, S1 and S2, with a projected separation of ~6 kpc,
making it a dual active galactic nuclei (AGN) candidate. Our new 15 GHz VLA
observations reveal that S1 is a double radio source centred around the optical
nucleus; its total extent is ~750 parsec and its average 1.4-8.5 GHz spectral
index is -0.81 +/- 0.06. S1 therefore, resembles a compact symmetric object
(CSO). The 15 GHz VLA image identifies the radio source at S2 to be a compact
core. Our radio observations therefore strongly support the presence of a dual
AGN in Mrk 212. The optical emission line flux ratios obtained from the
Himalayan Chandra Telescope (HCT) observations however, show that S1 and S2
both fall in the AGN + SF (star formation) region of the BPT diagram. Weak AGN
lying in the SF or AGN + SF intermediate regions in the BPT diagram have indeed
been reported in the literature; our sources clearly fall in the same category.
We find an extended radio structure in our newly reduced 8.5 GHz VLA data, that
is offset by ~1" from the optical nucleus S2. New deep FUV and NUV observations
with the Ultraviolet Imaging Telescope (UVIT) aboard AstroSat reveal SF knots
around S2 as well as kpc-scale tidal tails; the SF knots around S2 coincide
with the extended radio structure detected at 8.5 GHz. The radio spectral
indices are consistent with SF. Any possible association with the AGN in S2 is
unclear at this stage.
