C. Gheller et al., COLLISIONAL VERSUS COLLISIONLESS MATTER - A ONE-DIMENSIONAL ANALYSIS OF GRAVITATIONAL CLUSTERING, Monthly Notices of the Royal Astronomical Society, 283(4), 1996, pp. 1184-1196
We present the results of a series of one-dimensional N-body and hydro
dynamical simulations which have been used for testing the different c
lustering properties of baryonic and dark matter in an expanding backg
round. The numerical code is based on the piecewise parabolic method.
Initial Gaussian random density perturbations with a power-law spectru
m P(k)proportional to k(n) are assumed. We analyse the distribution of
density fluctuations and thermodynamical quantities for different spe
ctral indices n and discuss the statistical properties of clustering i
n the corresponding simulations. At large scales the final distributio
n of the two components is very similar while at small scales the dark
matter presents a lumpiness which is not found in the baryonic matter
. The amplitude of density fluctuations in each component depends on t
he spectral index n but that of the baryonic matter is always larger t
han the one in the dark component. This result is also confirmed by th
e behaviour of the bias factor, defined as the ratio between the rms o
f baryonic and dark matter fluctuations at different scales, which is
larger than unity in all the models we have considered. The final temp
eratures depend on the initial spectral index: the highest values (10(
8) K) are obtained for n = -1, and are in proximity to high-density re
gions. In the other models, the typical post-shock temperatures are sm
aller (10(5)-10(7) K).