  About half of the expected total baryon budget in the local Universe is
`missing'. Hydrodynamical simulations suggest that most of the missing baryons
are located in a mildly overdense, warm-hot intergalactic medium (WHIM), which
is difficult to be detected at most wavelengths. In this paper we explore
multi-wavelength synthetic observations of a massive galaxy cluster developed
in a full Eulerian-AMR cosmological simulation. A novel numerical procedure is
applied on the outputs of the simulation, which are post-processed with a
full-radiative transfer code that allows to compute the change of the intensity
at any frequency along the null-geodesic of photons. We compare the emission
from the whole inter-galactic medium (IGM) and from the WHIM component (defined
as the gas with a temperature in the range $10^5-10^7$ K) at three
observational bands associated to thermal X-rays, thermal and kinematic
Sunyaev-Zel'dovich effect, and radio emission. The synthetic maps produced by
this procedure could be directly compared with existing observational maps and
could be used as a guide for future observations with forthcoming instruments.
The analysis of the different emissions associated to a high-resolution galaxy
cluster is in broad agreement with previous simulated and observational
estimates of both gas components.
