Influence of baryons on spatial distribution of matter: higher order
  correlation functions
  Baryonic physical processes could leave non-negligible imprint on cosmic
matter distribution pattern. Series of high precision simulation data sets with
identical initial condition are employed for count-in-cell (CIC) analysis,
including one N-body dark matter run, one with adiabatic gas only and one with
dissipative processes. Variances and higher order correlation functions of dark
matter and gas are estimated. It is found that baryon physical processes mainly
affected dark matter distribution at scales less than $1h^{-1}$Mpc. In
comparison with the pure dark matter run, adiabatic process alone strengthens
variance of dark matter by \sim 10% at scale $0.1h^{-1}$Mpc, while $S_n$s of
dark matter deviate from pure dark matter case only mildly at a few
percentages. Dissipative gas run does not differ much to the adiabatic run in
dark matter variance, but renders significantly different $S_n$ parameters of
dark matter, bringing about more than 10% enhancement to $S_3$ at
$0.1h^{-1}$Mpc and $z=0$. Distribution patterns of gas in two hydrodynamical
simulations are prominently different. Variance of gas at $z=0$ decreases by
$\sim 30%$ in adiabatic simulation while by $\sim 60%$ in non-adiabatic
simulation at $0.1h^{-1}$Mpc, the attenuation is weaker at larger scales but
still obvious at $\sim 10h^{-1}$Mpc. $S_n$ parameters of gas are biased upward
at scales $< \sim 4h^{-1}$Mpc, dissipative processes give $\sim 84%$ promotion
at $z=0$ to $S_3$ at $0.1h^{-1}$Mpc against the moderate $\sim 7%$ in adiabatic
simulation. The clustering segregation we observed between gas and dark matter
could have intricate implication on modeling galaxy distribution and relevant
cosmological application demanding fine details of matter distribution in
strongly nonlinear regime.
