  We present a model calculation of transverse-momentum-dependent distributions
(TMDs) of gluons in the nucleon. The model is based on the assumption that a
nucleon can emit a gluon, and what remains after the emission is treated as a
single spectator particle. This spectator particle is considered to be
on-shell, but its mass is allowed to take a continuous range of values,
described by a spectral function. The nucleon-gluon-spectator coupling is
described by an effective vertex containing two form factors. We fix the model
parameters to obtain the best agreement with collinear gluon distributions
extracted from global fits. We study the tomography in momentum space of gluons
inside nucleons for various combinations of their polarizations. These can be
used to make predictions of observables relevant for gluon TMD studies at
current and future collider facilities.
