  We present a novel, virtual X-ray observatory designed to obtain synthetic
observations from hydro-numerical simulations, named PHOX. In particular, we
provide a description of the code constituting the photon simulator and of the
new approach implemented. We apply PHOX to simulated galaxy clusters in order
to demonstrate its capabilities. In fact, X-ray observations of clusters of
galaxies continue to provide us with an increasingly detailed picture of their
structure and of the underlying physical phenomena governing the gaseous
component, which dominates their baryonic content. Therefore, it is fundamental
to find the most direct and faithful way to compare such observational data
with hydrodynamical simulations of cluster-like objects, which can currently
include various complex physical processes. Here, we present and analyse
synthetic Suzaku observations of two cluster-size haloes obtained by processing
with PHOX the hydrodynamical simulation of the large-scale, filament-like
region in which they reside. Taking advantage of the simulated data, we test
the results inferred from the X-ray analysis of the mock observations against
the underlying, known solution. Remarkably, we are able to recover the
theoretical temperature distribution of the two haloes by means of the
multi-temperature fitting of the synthetic spectra. Moreover, the shapes of the
reconstructed distributions allow us to trace the different thermal structure
that distinguishes the dynamical state of the two haloes.
