  The galaxy CID-42 (CXOC J100043.1+020637.2) at z=0.359 has been proposed to
contain a promising candidate for a gravitational wave (GW) recoiling
supermassive black hole (SMBH), a slingshot SMBH from a triple-SMBH
interaction, or a kpc-scale dual Active Galactic Nuclei (AGN). These claims
were primarily based on a pair of bright cores separated by $\sim 0.''5$
resolved in optical HST imaging. Existing HST, Chandra and ground-based imaging
and spectroscopy are unable to confirm either scenario. With improved spatial
resolution, depth, and IR wavelength coverage, NIRCam multi-band imaging from
the COSMOS-Web JWST treasury program well resolved the two cores in CID-42,
revealing a significant stellar bulge for both cores (with stellar masses of
$\sim 10^{10}\,M_\odot$ for both). JWST imaging further revealed that only the
SE core contains an unobscured AGN point source, based on both image
decomposition and spectral energy distribution fitting. There is no evidence
for AGN activity in the NW core. These new observations unambiguously rule out
the GW-recoiling and slingshot SMBH scenarios, and establish CID-42 as a
low-redshift merging pair of galaxies, with only one active AGN in the system.
These results demonstrate the unparalleled capabilities of JWST (even with
imaging alone) in studying the galactic-scale environment of merging galaxies
and SMBHs.
