NOEMA observations support a recoiling black hole in 3C186
  3C186 is a powerful radio loud quasar (QSO) at the center of a cool-core
cluster at z=1.06. Previous studies reported evidence for a projected spatial
offset of ~1'' between the isophotal center of the galaxy and the point-source
QSO as well as a spectral shift of ~2000 km/s between the narrow and broad line
region of the system. In this work we report high-resolution molecular gas
CO(4-3) observations of the system taken with NOEMA interferometer. We clearly
detect a large reservoir of molecular gas, $M_{H_2}\sim8\times10^{10}~M_\odot$,
that is cospatial with the host galaxy and likely associated with a rotating
disk-like structure. We firmly confirm both the spatial offset of the galaxy's
gas reservoir with respect to the continuum emission of the QSO and the
spectral offset with respect to the redshift of the broad line region. Our
morphological and kinematical analysis confirms that the most likely scenario
to explain the 3C186 system is that the QSO is a kicked super-massive black
hole (SMBH), which we believe may have resulted from a strong gravitational
wave recoil as two SMBHs coalesced after the merger of their host galaxies.
