The clustering of baryonic matter. II: halo model and hydrodynamic
  simulations
  We recently developed a generalization of the halo model in order to describe
the spatial clustering properties of each mass component in the Universe,
including hot gas and stars. In this work we discuss the complementarity of the
model with respect to a set of cosmological simulations including hydrodynamics
of different kinds. We find that the mass fractions and density profiles
measured in the simulations do not always succeed in reproducing the simulated
matter power spectra, the reason being that the latter encode information from
a much larger range in masses than that accessible to individually resolved
structures. In other words, this halo model allows one to extract information
on the growth of structures from the spatial clustering of matter, that is
complementary with the information coming from the study of individual objects.
We also find a number of directions for improvement of the present
implementation of the model, depending on the specific application one has in
mind. The most relevant one is the necessity for a scale dependence of the bias
of the diffuse gas component, which will be interesting to test with future
detections of the Warm-Hot Intergalactic Medium. This investigation confirms
the possibility to gain information on the physics of galaxy and cluster
formation by studying the clustering of mass, and our next work will consist of
applying the halo model to use future high-precision cosmic shear surveys to
this end.
